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  • 1990-1994  (751)
  • 1985-1989
  • 1991  (751)
  • Chemical Engineering  (643)
  • pharmacokinetics
  • 1
    Digitale Medien
    Digitale Medien
    Distribution of mouse interferon-β in normal and brain tumour-bearing mice (1991)
    Springer
    Acta neurochirurgica 109 (1991), S. 46-51 
    Details
    ISSN: 0942-0940
    Schlagwort(e): Mouse interferon ; mouse glioma ; pharmacokinetics ; radioassay ; autoradiography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The distribution of125I-labelled recombinant mouse interferon-β (rMuIFN-β) in normal and glioma (203 glioma) bearing mice was studied by radioassay and macro-autoradiography at 15 and 30 min after a single intravenous injection. The level of rMuIFN-β in the spleen was about 20-fold higher than in serum. Concentrations higher than the serum level was detected in the lung, liver and kidney. The concentration of rMuIFN-β in the brain was 8% of the serum level and the concentration in the glioma 30 min after administration was about 10-fold higher than in normal mouse brain. Macro-autoradiographic study demonstrated a wide distribution range and selective uptake in glioma tissue. Furthermore, we found that mouse gliomas were sensitive to mouse IFN-β. Our findings demonstrate that in the mouse glioma model, intravenously administered interferon reaches the tumour.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01405697
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  • 2
    Digitale Medien
    Digitale Medien
    Clinical pharmacokinetics and tolerability of alpidem in healthy subjects given increasing single doses (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 369-374 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Alpidem ; Anxiolytics ; pharmacokinetics ; tolerance ; metabolites ; sedation ; adverse events
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In a double-blind, placebo-controlled, crossover experiment in 21 healthy male volunteers, aged 19 to 27 y, the pharmacokinetics and tolerance of the new anxiolytic drug alpidem (SL80.0342) and its three major metabolites were studied after single doses of 25, 50, 100 and 200 mg. Plasma concentrations of alpidem (in 20 subjects) and metabolites (in 6 subjects) were measured by HPLC over a period of 54 h after dosing. Cmax, tmax and AUC(0–54) and, when possible, t1/2 were determined for alpidem and metabolites and the dose linearity of the parameters was investigated. The time to peak of alpidem was dose independent in most subjects and was short (1–4 h); the mean values at the four dosing levels were 1.9, 1.7, 1.6 and 1.8 h. The peak concentration increased with the dose, the mean values being 17, 34, 88 and 115 ng · ml−1, respectively. In 50% of the subjects cmax tended to stabilize between the 100 and 200 mg dose. Dose linearity was also present for the AUC, which plateaued between the 100 and 200 mg dose in only 3 out of 20 subjects; the mean AUC was 119, 281, 669 and 1117 ng · ml−1 · h, respectively. The apparent half-life of elimination appeared to be dose independent, mean values at the increasing dosing levels being 18.7, 19.9, 18,1 and 17.9 h. A similar relationship between the kinetics parameters and dose of the alpidem was observed for the metabolites SL83.0912, SL80.0522 and SL83.0725. The formation of metabolites was not saturated as their AUCs relative to corresponding alpidem AUCs were not dose related. Thus the kinetics of alpidem and its three major metabolites were linear after doses of 25 to 200 mg. The drug was well tolerated by most of the subjects. Sedation and dizziness occurred mainly after the 100 and 200 mg doses.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314970
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  • 3
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of caffeine in patients with decompensated type I and type II diabetes mellitus (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 449-452 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Diabetes mellitus ; Caffeine ; pharmacokinetics ; P-450 mono-oxygenase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Diabetes may alter the pharmacokinetics of aminopyrine and antipyrine, which are used to assess liver function. Caffeine has recently been used to test liver function, but the effect of diabetes on caffeine kinetics is not known. The kinetics of caffeine has been examined in patients with decompensated Type I and Type II diabetes and in two age- and sex-matched control groups. In both types of diabetes the apparent caffeine clearance, half-life, and apparent volume of distribution were similar to controls. It is concluded that decompensated diabetes does not influence the cytochrome P-448 mono-oxygenase system responsible for caffeine metabolism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00626367
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  • 4
    Digitale Medien
    Digitale Medien
    Dopamine pharmacokinetics in critically ill newborn infants (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 593-597 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Dopamine ; Newborns ; critically ill patients ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Dopamine is frequently used in critically ill newborn infants for treatment of shock and cardiac failure, but its pharmacokinetics has not been evaluated using a specific analytical method. Steady-state arterial plasma concentrations of dopamine were measured in 11 seriously ill infants receiving dopamine infusion, 5–20 μg · kg−1 · min−1, for presumed or proven sepsis and hypotensive shock. Steady-state concentrations of dopamine ranged from 0.013–0.3 μg/ml. Total body clearance averaged 115 ml · kg−1 · min−1. The apparent volume of distribution and elimination half life averaged 1.8 1 · kg−1 and 6.9 min, respectively. No relationship was observed between dopamine pharmacokinetics and gestational age, postnatal age or birthweight. Substantial interindividual variation was seen in dopamine pharmacokinetics in seriously ill infants, and plasma concentrations could not be predicted accurately from its infusion rate. Marked variation in clearance explains in part, the wide dose requirements of dopamine needed to elicit clinical response in critically ill newborn infants.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00279976
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  • 5
    Digitale Medien
    Digitale Medien
    The concentration-dependent disposition and kinetics of inulin (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 619-624 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Inulin ; pharmacokinetics ; half life ; distribution ; concentration-dependent clearance ; healthy subjects ; chronic renal failure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The disposition of inulin was studied in 30 healthy male and 10 healthy female volunteers, and 10 patients with stable chronic renal failure (mean creatinine clearance 45 ml·min−1) following intravenous infusion of 70 mg·kg−1 over 5 min. Plasma concentrations fell rapidly initially but the rate of decline decreased continuously over 8 h and a linear terminal elimination phase could not be identified. Inulin was excreted rapidly by the subjects with normal renal function and 97.3% of the dose was recovered in the urine in 8 h. There was a progressive highly significant fall in the renal clearance of inulin after 2 h as plasma concentrations fell below about 150 mg·l−1. Six to 8 h after administration the clearance was less than 50% of the initial value in the healthy volunteers and the corresponding fall in the renal patients was 33%. The concentration-dependent renal clearance of inulin was confirmed in “step-up” and “step-down” constant infusion studies in which clearances were measured at mean plasma concentrations ranging from 35.2 to 186.7 mg·l−1. These studies virtually excluded time, changes in posture and urine flow rate as important factors. There was no statistically significant fall in clearance during the first 2 h and kinetic analysis was based on data obtained over this time. Under these conditions the mean plasma half life, volume of distribution (Vss) and total body clearance of inulin in the healthy males, healthy females and patients with chronic renal failure were 73.2, 65.5 and 172.4 min, 10.5, 9.6 and 8.81·70 kg−1 and 113.3, 111.5 and 43.3 ml·min−1·70 kg−1 respectively. There were no sex differences in any of the kinetic variables. The mechanism of the concentration-dependent clearance of inulin is unknown but the findings are consistent with saturable renal tubular reabsorption. Care is required with the use of inulin for measurement of the glomerular filtration rate by the single injection technique.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00279982
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  • 6
    Digitale Medien
    Digitale Medien
    Effect of ampicillin on mefloquine pharmacokinetics in thai males (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 631-633 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Mefloquine ; ampicillin ; Thai subjects ; pharmacokinetics ; enterohepatic recycling ; drug interaction ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The kinetics of a single oral dose of mefloquine given either alone or with ampicillin has been studied in 8 healthy Thai male volunteers. There was a significantly higher maximum whole blood mefloquine concentration after coadministration with ampicillin (1648 vs 1228 ng·ml−1), as well as a significantly reduced terminal half life (15.3 vs 17.7 days), mean residence time (20.1 vs 23.4 days) and volume of distribution at steady state (14.1 vs 19.4 l·kg−1). Although there was no significant change in the AUC from zero time to infinity, the AUC from zero time to 5 days was significantly increased by ampicillin (4.86 vs 3.27 μg·ml−1 day). These changes in mefloquine disposition after antibiotic treatment may be due both to an increase in fractional bioavailability and a reduction in the enterohepatic recycling of mefloquine.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00279985
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  • 7
    Digitale Medien
    Digitale Medien
    Lack of effect of multiple dose sucralfate on the pharmacokinetics of roxatidine acetate (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 637-638 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Roxatidine acetate ; sucraflate ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00279987
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  • 8
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of halofantrine and n-desbutylhalofantrine in patients with falciparum malaria following a multiple dose regimen of halofantrine (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 161-164 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Halofantrine ; Malaria falciparum ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Halofantrine is a new blood schizontocidal drug used for the treatment of multidrug-resistant falciparum malaria. The pharmacokinetics of halofantrine (HAL) and its principal metabolite, N-desbutylhalofantrine (BHAL), was investigated in 6 adult male patients of Melanesian origin with uncomplicated falciparum malaria. The patients received 500 mg of halofantrine hydrochloride at times 0, 6 and 12 h (total 1.5 g). All patients responded to treatment with a mean parasite clearance time of 52.7 h and a mean fever clearance time of 33.8 h. The following kinetic parameters (mean values) were determined for HAL and BHAL, respectively: maximum plasma concentration (Cmax)=896 and 491 ng·ml−1; time to reach the Cmax (tmax)=15 and 56 h; elimination half-life (t1/2)=91 and 79 h and the mean residence time (MRT)=71 and 102 h. Based on the clinical response the plasma concentrations of HAL and BHAL were adequate for the treatment of uncomplicated falciparum malaria in the 6 patients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265910
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  • 9
    Digitale Medien
    Digitale Medien
    Fosinopril pharmacokinetics and pharmacodynamics in chronic ambulatory peritoneal dialysis patients (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 165-169 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Fosinopril ; fosinoprilat ; CAPD ; ACE-inhibitor ; pharmacokinetics ; pharmacodynamics ; peritoneal dialysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics and pharmacodynamics of fosinoprilat, the diacid of fosinopril sodium, a new angiotensin-converting enzyme (ACE) inhibitor, were investigated after the oral administration of 10 mg of fosinopril sodium to 6 chronic ambulatory peritoneal dialysis (CAPD) patients. The results from 1 patient are reported separately because of the presence of concomitant liver dysfunction. The mean t1/2, Cmax, tmax, and AUC values for 5 of the CAPD patients were 19.5 h, 202 ng·ml−1, 4.8 h, and 3.19 μg·h·ml−1, respectively. Values for 1 CAPD patient with liver dysfunction were t1/2 of 65.4 h, Cmax of 182 ng·ml−1, tmax of 9 h, and AUC of 18.1 μg·h·ml−1. Peritoneal clearance of fosinoprilat was negligible, ranging from 0.07 to 0.23 ml·min−1. Serum ACE activity remained significantly suppressed at 24 and 48 h after fosinopril sodium administration with mean decreases from baseline of 94.2% and 70.6%, respectively. ACE activity was suppressed to an even greater degree in the patient with liver dysfunction, remaining 97% inhibited 72 h after drug administration. Plasma renin activity (PRA) increased and plasma aldosterone concentrations decreased following drug administration. Mean arterial pressure did not change appreciably throughout the study. Dosage reductions may not be necessary in the majority of dialysis patients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265911
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  • 10
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of intravenous bisoprolol in obese and non-obese volunteers (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 171-174 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Bisoprolol ; pharmacokinetics ; obesity ; blood flow
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of a single i. v. dose of dlbisoprolol 0.16 mg·kg−1 ideal body weight has been studied in 8 obese women (mean weight 91 kg; 161% of ideal body weight) and 8 non-obese women (51 kg; 94% of ideal body weight). Compared to the controls, the obese subjects showed an increase in the total apparent volume of distribution (Vz) (182 vs 135 1) and a decrease in Vz per kg body weight (2 vs 2.7 l·kg−1). There was a negative correlation between Vz l·kg−1 and the percentage of ideal body weight (r=−0.672). Total body clearance was increased, but t1/2 and renal clearance was unchanged. It is concluded that tissue diffusion of bisoprolol in obese subjects is limited, despite its lipophilicity, possibly because of alteration in the blood flow to adipose tissue produced by bisoprolol.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265912
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  • 11
    Digitale Medien
    Digitale Medien
    Steady state pharmacokinetics of hydrolysed bopindolol in young and elderly men (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 175-178 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Bopindolol ; pharmacokinetics ; beta-adrenoceptor blocker ; age ; hydrolysed bopindolol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Steady-state pharmacokinetic parameters of the new, long-acting beta-adrenoceptor blocker bopindolol have been measured in 17 young and 20 elderly healthy men. The t1/2β and the AUC(0→24 h) of hydrolysed bopindolol (the active metabolite) were both increased (40% and 26%, respectively) in the elderly subjects but tmax, Cmax and CL/f were not altered. However, after adjusting the parameters to allow for the different average body weights of the two groups, Cmax and CL/f became significantly different (+29% and −30%, respectively). AUC(0→24 h) was increased by 41%. The changes of up to 41% in pharmacokinetic parameters were smaller than the alterations of 50–100% usually seen when titrating doses of antihypertensive drugs. The clinical relevance of the effects was not examined, but similar changes have been reported for other beta-blockers which did not appear to be clinically relevant and did not affect the dosage required to treat hypertension.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265913
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  • 12
    Digitale Medien
    Digitale Medien
    Dose-dependent absorption and elimination of cefadroxil in man (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 179-183 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Cefadroxil ; saturable absorption ; saturable renal tubular reabsorption ; cephalexin ; competitive inhibition ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetic behaviour of cefadroxil was dose-dependent in healthy male volunteers following the oral administration of single doses of 5, 15, and 30 mg · kg−1. As the dose of cefadroxil increased from 5 to 15 and 30 mg · kg−1, the peak plasma concentrations, normalized to 5 mg · kg−1, decreased significantly from 15.1 to 10.7 and 7.6 mg·l−1, while the corresponding normalized areas under the plasma concentration-time curves from 0 to 2 h decreased significantly from 1258 to 946 and 801 min·mg·l−1. When the same subjects were given 5 mg·kg−1 of cefadroxil together with 45 mg·kg−1 of cephalexin, the absorption of cefadroxil was slowed to a similar or greater extent than with the high dose of cefadroxil. Although the absorption rate decreased as the dose increased, the systemic availability of cefadroxil was essentially complete at all doses, as judged by the 24 h urinary recoveries of the antibiotic. Kinetic analysis of the plasma concentration-time curves gave the best fit with a zero-order followed by a first-order absorption process, consistent with saturable intestinal absorption of cefadroxil. The elimination rate of cefadroxil was directly related to dose and plasma concentrations, and the clearance at the dose of 5 mg·kg−1 was significantly increased by the simultaneous administration of high-dose cephalexin. The renal clearance of cefadroxil ranged from 98 ml·min·l−1 at total plasma cephalosporin (cefadroxil + cephalexin) concentrations less than 2.5 mg·l−1 to 156 mg·l−1 at concentrations greater than 40 mg·l−1. These findings are consistent with saturable active gastrointestinal absorption and renal tubular reabsorption of cefadroxil, with competitive inhibition of both processes by cephalexin.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265914
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  • 13
    Digitale Medien
    Digitale Medien
    Interaction of ORG 10172, a low molecular weight heparinoid, and digoxin in healthy volunteers (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 245-250 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Org 10172 ; Digoxin ; heparinoid ; pharmacokinetics ; pharmacodynamics ; drug interactions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Potential pharmacokinetic and pharmacodynamic interactions between a new low molecular weight heparinoid Org 10172 (bolus injection of 3250 anti-Xa units) and digoxin (0.25 mg once daily for 8 days) were studied in 6 healthy male volunteers using an open, randomised three-way cross-over design. Digoxin produced a slight increase in clearance of anti-Xa activity from 4.3 to 4.8 ml·min−1, while plasma anti-thrombin and thrombin generation inhibiting (TGI) activity remained unchanged. Digoxin did not affect the actions of Org 10172 on the clotting tests. In the presence of Org 10172 there was a reduction in the AUC of digoxin during one dosing interval after the seventh digoxin tablet from 20 to 17 ng·ml−1·h, and a significant reduction in the average serum digoxin conentration. Since renal digoxin clearance was not significantly changed this probably might be due to a change in the non-renal clearance of digoxin. Atrio-ventricular node conduction, as measured by PR-time intervals, remained unchanged during all three treatments. In conclusion, although the pharmacokinetics of Org 10172 and digoxin were slightly changed by the combination, it is probably safe to administer Org 10172 and digoxin simultaneously. The clinical relevance of the slight decrease in plasma anti-Xa activity levels cannot yet be defined.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315437
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  • 14
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of tiaprofenic acid in children after a single oral dose (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 251-253 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Tiaprofenic acid ; children ; pharmacokinetics ; NSAID
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary. Twelve healthy children in three age groups anaesthetized for minor surgery were given a single oral dose of tiaprofenic acid (3 mg · kg−1) (TA). Seven blood samples and zero to 8 and 8 to 24 h urines were collected. TA concentrations in plasma and urine were measured by HPLC. No significant difference was found between the age groups in the kinetic parameters of TA and no correlation was found between these parameters and age; tmax=2.12h, Cmax=8.78mg · l−1, AUC(0→8 h) 33.9mg · h · l−1, AUC=39.3 mg · h · l−1, t1/2=2.35 h, Vz=0.319 l · kg−1, CL=0.094 l · h−1 · kg−1. Renal clearance was 14 ml · h−1. kg−1. 33% of the TA dose was recovered in the 24 h urine, 48% of which was conjugated, whereas in adults, TA is only found in urine as conjugates. The apparent plasma clearance was significantly higher (56%) than in 12 healthy adults given 1.5 mg · kg−1 TA. Volume of distribution and t1/2 did not significantly differ between children and adults. Since no relationship has been established between plasma TA and either efficacy or toxicity, a different dose regimen cannot be recommended in 3–11 year-old children from that in adults.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315438
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  • 15
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of midazolam in children: comparative study of intranasal and intravenous administration (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 355-357 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Midazolam ; pharmacokinetics ; intranasal ; intravenous ; children ; bioavailability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Twelve children 1–5 y old were randomly assigned to receive midazolam 0.2 mg·kg−1 either by the intravenous (IV) or intranasal (IN) routes. After IN administration the rapid onset of absorption was observed (tmax 12 min). After both routes of administration the half-life was similar (2.2 h IN and 2.4 h IV). After IN administration the apparent plasma clearance and volume of distribution were about twice as high as after IV administration. The results are consistent with an estimated mean bioavailability of 55%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314967
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  • 16
    Digitale Medien
    Digitale Medien
    Antipyrine kinetics in undernourished diabetics (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 359-361 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Diabetes ; Antipyrine ; undernutrition ; drug metabolism ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In developing countries diabetics frequently suffer from varying grades of malnutrition. The combined effect of malnutrition and non-insulin dependent diabetes (NIDDM) on the drug metabolising enzyme system has been evaluated using antipyrine as a protodrug. All the patients were under treatment and their plasma glucose values were within normal limits. The AUC of antipyrine was similar in all the groups. Although none of the kinetic parameters was altered in normal diabetics, the clearance of antipyrine was decreased and its half life was prolonged, with an increase in volume of distribution, in undernourished diabetics compared to undernourished controls. The results indicate that diabetes per se may not influence antipyrine kinetics when the blood glucose is well under control, but in the presence of undernutrition, it significantly alters the disposition of the drug.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314968
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  • 17
    Digitale Medien
    Digitale Medien
    Lack of effect of paracetamol on the pharmacokinetics and metabolism of codeine in man (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 379-382 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Codeine ; paracetamol ; codeine-6-glucuronide ; pharmacokinetics ; metabolism ; partial clearance ; drug interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Plasma and urine concentrations of codeine and its measurable metabolites were determined by HPLC in six healthy subjects after a single 30 mg oral dose of codeine either alone or after 7 doses of 1 g paracetamol 8 hourly. After codeine alone, the t1/2 (h), AUC (μmol·l−1·h) and CLR (ml·min−1) for codeine were 2.2, 0.81, and 252 respectively. These were not significantly altered by paracetamol: 2.2, 0.84, and 291 respectively. For codeine-6-glucuronide the values were 2.4, 22.0, and 29.7 respectively. These were not significantly different from those after codeine plus paracetamol: 2.4, 21.9, and 39.6. There were no significant differences between the two treatments in the apparent partial clearances (ml·min−1) of codeine to morphine (88 codeine alone, 70 codeine plus paracetamol), to norcodeine (71 codeine alone, 88 codeine plus paracetamol), and to codeine-6-glucoronide (820 codeine alone, 1022 codeine plus paracetamol). The urinary excretion of codeine-6-glucuronide, morphine, norcodeine, and codeine were not significantly different between the two treatments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314972
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  • 18
    Digitale Medien
    Digitale Medien
    Relationship between renal function and disposition of oral cefixime (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 579-583 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Cefixime ; renal failure ; pharmacokinetics ; volunteers ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of cefixime following a single oral dose of 200 mg have been investigated in 6 normal subjects and in 22 patients with various degrees of renal insufficiency. Serum and urine samples were collected between 0 and 72 h and were subjected to two methods of analysis: bioassay and HPLC. There was a linear relationship between the two sets of results from 228 samples. This result suggests that none of the metabolites, which may accumulte in uraemic patients, has antibacterial activity. In normal subjects, the peak serum level (Cmax) was 2.50 μg·ml−1 at 2.83 h (tmax); the apparent elimination half-life (t1/2) was 3.73 h; the apparent total body clearance (CL·f−1) was 154 ml·min−1, the mean renal clearance (CLR) was 39.1 ml·min−1 and the apparent fraction of the dose recovered in 24 h urine was 0.22. In uraemic patients, Cmax and tmax were slightly increased and t1/2 was increased to 12–14 h in patients with an endogenous creatinine clearance below 20 ml·min−1. The apparent volume of distribution was decreased. Apparent total and renal clearances were lower in proportion to the degree of renal insufficiency. Linear relationships were found between CL/f, CLR and creatinine clearance (CLCR). The findings suggest that the dose of cefixime needs to be reduced only in patients with severe renal failure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314988
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  • 19
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of chlormezanone in elderly patients (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 603-607 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Chlormezanone ; pharmacokinetics ; elderly
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of Chlormezanone (CM) has been determined after a single oral dose of 400 mg CM in 5 young volunteers (28 y) and in 8 elderly patients (79 y). In the young subjects, CM was rapidly absorbed and distributed, and was slowly eliminated with a half-life of 38 h major metabolites were not detected in plasma or urine. Only 3% of CM was excreted unchanged in urine. In elderly patients absorption was delayed but not reduced; the Cmax and AUC did not differ from those in younger subjects, the elimination rate was reduced compared to the younger subjects (mean 54 h). The increase was in part related to the reduction in renal function and metabolism observed in aging. However, the change in pharmacokinetics was moderate and no adjustment in dosage seems necessary for treatments of limited duration in elderly patients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314993
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  • 20
    Digitale Medien
    Digitale Medien
    Clinical chronopharmacology of oral sustained-release isosorbide-5-mononitrate in healthy subjects (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 71-75 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Isosorbide-5-mononitrate ; sustained-release formulation ; pharmacokinetics ; cardiovascular effects ; chronopharmacology ; healthy volunteers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In 10 healthy male subjects the pharmacokinetics and haemodynamic effects of sustained-release isosorbide-5-mononitrate 60 mg (IS-5-MN) were studied after oral administration at two different times in the day (08.00 h and 20.00 h). Effects on blood pressure and heart rate after 3 min standing upright were measured in relation to the individual circadian control values. The pharmacokinetic parameters (Cmax, tmax, AUC, t1/2) did not differ after morning and after evening dosing, tmax being 5.2 h and 4.9 h, respectively. In contrast, the cardiovascular effects of IS-5-MN were clearly circadian phase-dependent. The maximum decrease in blood pressure decrease and increase in heart rate occurred significantly earlier after the evening (BPsys 2.8 h; BPdia 2.9 h; HR 3.8 h) than after the morning dose (BPsys 5.0 h; BPdia 6.0 h; HR 5.2 h). Thus, the peak haemodynamic effects coincided with the peak drug concentration after the morning dose, whereas the peak effect was in advance of the peak drug concentration after the evening dose of IS-5-MN. The data provide evidence of circadian phase-dependency in the dose-response relationship of oral IS-5-MN.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315142
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  • 21
    Digitale Medien
    Digitale Medien
    Pitfalls of pharmacokinetic dosage guidelines in renal insufficiency (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 87-93 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Pharmacotherapy ; renal insufficiency ; pharmacokinetics ; renal drug elimination ; drug monitoring ; dosage guidelines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary As the renal elimination of most drugs is closely correlated with the endogenous creatinine clearance, it is possible to use this parameter of kidney function to adjust drug dosage in renal failure. However, this simple procedure neglects possible changes in the volume of distribution, plasma protein binding, drug metabolism, intestinal absorption, and pharmacodynamics in renal insufficiency, as well as the occurrence of biologically active drug metabolities. Because of these uncertainties in critical cases the validity of the dosage calculated using the creatinine clearance should be checked by clinical surveillance and measurements of drug blood concentrations. Further, pharmacokinetic dosage guidelines based on the individual creatinine clearance may not be applicable to diuretics and drugs which have markedly differing kinetics of pharmacodynamic effects and blood levels.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315145
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  • 22
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of the anti-inflammatory drug ximoprofen in healthy subjects and in disease states (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 101-106 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Ximoprofen ; pharmacokinetics ; normal subjects ; hepatic disease ; renal disease
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of ximoprofen, a potent new non-steroidal anti-inflammatory agent, has been investigated in normal healthy subjects and in patients with hepatic or renal disease. After intravenous infusion of 22.8 mg to healthy subjects, plasma ximoprofen concentrations declined in a polyexponential manner with a terminal phase half-life of 1.9 h. The systemic clearance of ximoprofen was 115 ml·min−1 and the volumes of distribution were 18.0 l Vz and 13.8 l Vss. Ximoprofen was 80–90% bound to plasma proteins. The systemic availabilities (f) of orally and rectally administered doses of 30 mg of ximoprofen were 98% and 56% respectively and, in the case of the rectal dose, absorption appeared to be prolonged leading to “flip-flop” kinetics. After single oral doses of 30 mg of ximoprofen to patients with hepatic disease, half-life (2.2 h), peak plasma concentrations (1.55 μg·ml−1 cf 1.04 μg·ml−1 in healthy subjects) and areas under the curve (6.12 μg·h·ml−1 cf 3.54 μg·h·ml−1 in healthy subjects) were significantly different from those in healthy subjects. After single oral doses of 30 mg of ximoprofen to patients with renal disease, pharmacokinetic parameters of half-life (4.0 h), mean residence time (6.0 h) and area under the curve (9.2 μg·h·ml−1) were significantly different from those in healthy subjects. There were no significant differences in pharmacokinetic parameters between patients having differing degrees of renal disease. These data nevertheless suggest that accumulation of ximoprofen in hepatic or renal disease would be of slight or negligible clinical relevance and that no alteration of the dose regimen (up to 15 mg twice daily) may be required when ximoprofen is administered in these disease states.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315147
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  • 23
    Digitale Medien
    Digitale Medien
    CSF Baclofen levels after intrathecal administration in severe spasticity (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 363-365 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Baclofen ; severe spasticity ; pharmacokinetics ; CSF ; intrathecal injection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetic parameters in the CSF of baclofen given to 4 patients as an intrathecal bolus are reported. Considerable inter-individual variability in the parameters was observed. The elimination half-life ranged from 0.9 to 5 h and the clearance from 0.013 to 0.08 l·h−1. In order to optimize treatment, it is suggested that CSF baclofen levels be matched to changes in Hoffman's monosynaptic reflex (H reflex).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265844
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  • 24
    Digitale Medien
    Digitale Medien
    Evaluation of proposed sulphoxidation pathways of carbocysteine in man by HPLC quantification (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 387-392 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Carbocysteine ; pharmacogenetics ; drug metabolism ; sulphoxidation ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A quantitative study has been made of the metabolism of S-carboxymethyl-L-cysteine (CMC) and its sulphoxides in volunteers by HPLC. Precolumn derivatization was applied prior to gradient reversed phase HPLC separation and fluorescence detection. For CMC and its metabolites containing a primary amino group the reagent 9-fluorenylmethylchloroformate was used. The other metabolites of CMC were derivatized at their carboxylic group with 1-pyrenyldiazomethane to give stable fluorescent products. Urine samples were collected for 8 h after oral administration of 1.125 g CMC to 33 healthy volunteers. Elimination of CMC in urine as sulphoxides did not account for more than 1% of the dose in any of the volunteers. Thus, CMC-sulphoxide metabolites are not quantitatively important. Recovery of the original substance in 8-hour urines ranged from 10 to 30% and a further 2 to 20% was recovered as the metabolite thiodiglycolic acid. Oral doses of 0.19, 1.125, and 2.25 g CMC in a second group of 12 healthy volunteers did not reveal dose dependence of the urinary excretion of the sulphoxides or of thiodiglycolic acid. Serum concentration-time-curves of CMC, (S)- and (R)-CMC sulphoxide were measured in a group of 9 healthy volunteers. The CMC sulphoxides in serum reached 1.5% of the parent substance after 4 hours. The ratio of CMC to its sulphoxide metabolites was similar in serum and urine. Pharmacogenetic polymorphism of sulphoxidation was not confirmed by the specific HPLC methods used.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265849
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  • 25
    Digitale Medien
    Digitale Medien
    Interaction of metoprolol with lorazepam and bromazepam (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 405-409 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Metoprolol ; lorazepam ; bromazepam ; interaction ; psychomotor tests ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The interaction between metoprolol and bromazepam and lorazepam was studied in 12 healthy male volunteers aged 21–37 years. Metoprolol had no significant effect on the pharmacokinetics of bromazepam or lorazepam. However, bromazepam AUC was 35% higher in the presence of metoprolol. Bromazepam enhanced the effect of metoprolol on systolic blood pressure but not on diastolic blood pressure or pulse rate. Lorazepam had no effect on either blood pressure or pulse. Metoprolol did not enhance the effect of bromazepam on the psychomotor tests used in this study. Metoprolol caused a small increase in critical flicker fusion threshold with lorazepam but had no effect on the other tests. Lorazepam (2 mg) was more potent than bromazepam (6 mg) in the doses used in this study. The interaction of metoprolol with bromazepam and lorazepam is unlikely to be of clinical significance. No change in dose is necessary when using these drugs together.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265852
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  • 26
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of ibuprofen in febrile children (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 427-428 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Ibuprofen ; children ; fever ; pharmacokinetics ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Ibuprofen may be an alternative to acetaminophen to control fever in children but little is known about its pharmacokinetics in pediatric patients. We studied 17 patients (age 3–10 yr) with fever; the most prevalent diagnoses were streptococcal pharyngitis and otitis media. Ibuprofen liquid was given as a single dose, 5 mg/kg (9 patients) or 10 mg/kg (8 patients). Multiple blood samples were collected over 8 hours and analyzed by HPLC. The maximum observed serum concentrations of ibuprofen ranged from 17–42 μm·ml−1 at 5 mg·kg−1 and 25–53 μm·ml−1 at 10 mg·kg−1 doses. Pharmacokinetics did not appear to be affected by ibuprofen dose. Mean tmax, oral clearance and elimination half life were 1.1 h, 1.2 ml·min−1·kg−1, and 1.6 h, respectively in patients at 5 mg·kg−1 doses; the corresponding values were 1.2 h, 1.4 ml·min−1·kg−1, and 1.6 h in those receiving 10 mg·kg−1 doses. There was no relationship between age and ibuprofen kinetics. No adverse effects occurred in any patients. These data suggest that ibuprofen pharmacokinetics may not be affected by dose between 5 and 10 mg/kg or age between 3 and 10 years.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265858
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  • 27
    Digitale Medien
    Digitale Medien
    Disposition of epirubicin and metabolites with repeated courses to cancer patients (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 481-487 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Epirubicin ; pharmacokinetics ; plasma concentrations ; cancer patients
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Thirteen cancer patients were studied following a total of 41 courses of epirubicin (EPI) (38–50 mg·m−2, mean 49.2 mg·m−2, administered by a 60 min infusion), together with other cancer chemotherapeutic agents. The aim was to consider the disposition of EPI and metabolites following subsequent courses as it has been reported that doxorubicin (the 4′-epimer parent of EPI) clearance is increased following the first administration. We have observed that EPI-glucuronide accounted for a mean 78.0%, epirubicinol 0.2% and epirubicinol-glucuronide 19.3% and that parent EPI accounted for only 2.4% of the EPI-compounds measured (mean of all patients and courses) for the 3 h period immediately following the infusion. These data confirm the rapid metabolism of EPI and the dominance of the glucuronidation metabolite pathway (which is not available to doxorubicin) and are compared with the metabolite profile observed in other reports. Large inter- and intra-individual variability in area under the plasma concentration/time curve were observed with no clear evidence of any consistent directional trend for such fluctuations, suggesting that factors contributing to EPI disposition are multivariate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315227
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  • 28
    Digitale Medien
    Digitale Medien
    Polymorphic flecainide disposition under conditions of uncontrolled urine flow and pH (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 155-162 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Flecainide ; sparteine/debrisoquine polymorphism ; metabolism ; enantiomers ; pharmacokinetics ; stereoselectivity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of R- and S-flecainide have been determined in five poor (PM) and five extensive (EM) metabolisers of sparteine/debrisoquine under conditions of uncontrolled urine flow and pH. The half-lives of R- and S-flecainide in PMs (R 19.3 h; S 16.1 h) were approximately twice those observed in EMs (R 8.8 h; S 9.1 h). The apparent oral clearances of R- and S-flecainide were lower in PMs (R 313 ml·min−1; S 379 ml·min−1) than in EMs (R 783 ml·min−1; S 828 ml·min−1). The renal clearance, however, was comparable for both enantiomers in both EMs and PMs, and therefore the phenotypic differences in flecainide disposition observed must be due to differences in metabolic clearance. The nonrenal clearance of both enantiomers was significantly lower in poor (R 123 ml·min−1; S 201 ml·min−1) relative to extensive metabolisers (R 533 ml·min−1; S 586 ml·min−1). The partial clearance to the two major metabolites meta-O-dealkylated flecainide (MODF) and the meta-O-dealkylated lactam of flecainide (MODLF) was significantly lower in poor (62 ml·min−1) than extensive (267 ml·min−1) metabolisers. The impairment in flecainide metabolism in poor metabolisers of sparteine/debrisoquine has therefore been confirmed. Under conditions reflecting the clinical situation the difference in disposition between EMs and PMs would be considerable. However, it may be predicted that at standard doses concentrations greater than 1000 ng·ml−1 would not be attained in the PMs studied. The serum protein binding of R- and S-flecainide was studied in each subject and no differences between the enantiomers or the phenotypes were observed (Free fraction EM: R 0.43; S 0.42; PM R: 0.46; S: 0.46). Enantioselective disposition was noted in all PMs studied, due to a significantly lower nonrenal clearance of the R-enantiomer. In extensive metaboliser subjects, considerable interindividual variation in the enantioselective disposition of flecainide was noted, ranging from metabolism favouring either enantiomer to the absence of any selectivity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280070
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  • 29
    Digitale Medien
    Digitale Medien
    The relationships between dose and concentration of tolbutamide and insulin and glucose responses in patients with non-insulin-dependent diabetes (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 163-168 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Tolbutamide ; diabetes mellitus ; non-insulin dependent ; pharmacokinetics ; pharmacodynamics ; glucose ; insulin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary It is uncertain how the hypoglycaemic effect of sulphonylureas varies with drug concentration in patients with non-insulin-dependent diabetes mellitus. The interrelationship of tolbutamide dosage and concentration, and glucose and insulin concentrations were therefore examined in 54 out-patients (the observational group) and in 20 patients studied under controlled conditions (the experimental group). In the observational group, tolbutamide concentration depended significantly on the daily dose, time from dose to sampling, body weight, and age. Blood glucose and insulin concentration were related, but were independent of tolbutamide concentration. In the experimental group, peak, but not pre-dose, tolbutamide concentration, depended on dose and on body mass index. Fasting and maximum post-prandial blood glucose concentration were positively correlated with maximum tolbutamide concentration, probably because tolbutamide dosage was highest in those with the poorest response. In the subset with a fasting blood glucose concentration of less than 8 mmol·l−1, neither glucose nor insulin concentrations depended significantly on tolbutamide concentrations. Tolbutamide concentration does not directly determine hypoglycaemic response in outpatients, and therapeutic monitoring of drug concentrations would not improve the management of such patients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280071
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  • 30
    Digitale Medien
    Digitale Medien
    Effect of duration of levodopa/decarboxylase inhibitor therapy on the pharmacokinetic handling of levodopa in elderly patients with idiopathic Parkinson's disease (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 459-462 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Levodopa/decarboxylase inhibitor ; Parkinson's Disease ; pharmacokinetics ; duration of therapy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We address, from a pharmacokinetic viewpoint, the important question of why some patients with clinical idiopathic Parkinson's disease experience a fall off in benefit from levodopa maintenance therapy. Thirteen such patients, of mean age 78 y, without overt fluctuations in motor control in temporal relation to dosing with a levodopa/decarboxylase inhibitor combination, were studied. Levodopa (currently 400 to 800 mg daily) had been started at between 61 and 81 y of age, the mean duration of therapy being 54 months. Plasma concentrations of levodopa and its peripheral metabolite, 3-0-methyldopa, were measured before a morning dose of levodopa (100 mg)/carbidopa (25 mg) and at hourly intervals for 6 h after. There was a significant negative regression between duration of levodopa therapy (but not age or severity of disease) and the area under the plasma concentration/time curve (AUC) for levodopa attributed to the test dose. A significant negative regression was also seen of duration of therapy on the dose absorbed per unit distribution volume, but not on the elimination rate constant, indicating a decrease in bioavailability and/or an increase in distribution volume with duration. There was a tendency for the plasma 3-0-methyldopa concentration, standardised for daily dose, [30MD], to increase with duration of therapy. Although, the regression of duration on [30MD] did not reach statistical significance, that on the ratio, [30MD]/AUC, did so at the 0.01 level. The amount by, and time for which, the plasma levodopa concentration exceeds any critical threshold for the competitive active uptake process into the brain may thus decrease with duration of therapy. This may explain in part the limited reversal of the neurological deficit, which is more typical of later onset Parkinsonism, and, possibly, the decrement in biological half time with duration of therapy, typical of early onset disease. 3-0-Methyldopa is known to compete for active uptake with levodopa; the ratio, [30MD]/AUC, may be a measure of this competition. Intrinsic activity of neuronal uptake mechanisms, capacity of the basal ganglia for storage of dopamine, and post synaptic neuronal activity may, of course, also be determinants of clinical outcome.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00626369
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  • 31
    Digitale Medien
    Digitale Medien
    Elimination of flecainide as a function of urinary flow rate and pH (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 61-63 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Flecainide ; dose adjustment ; urinary pH ; urinary flow rate ; renal elimination ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In order to evaluate the influence of urinary flow rate at different pH values on the pharmacokinetics of the basic antiarrhythmic drug flecainide 7 healthy men received 50 mg flecainide under 4 different conditions: 1. acidic urine (pH 5) and a high fluid load (125 ml · h−1) 2. acidic urine (pH 5) and a low fluid load (25 ml · h−1) 3. alkaline urine (pH 8) and a high fluid load (125 ml · h−1) 4. alkaline urine (pH 8) and a low fluid load (25 ml · h−1) At acidic pH the half-life, the amount of unchanged drug in the urine (Ae), renal clearance (CLR) and area under the curve (AUC) were independent of the fluid load. At alkaline pH Ae (5.8 vs 2.6 mg) and CLR (73 vs 33 ml · min−1) were significantly affected by fluid load (high vs low), whereas half-life and AUC were not different (15.7 vs 16.0 h, 1480 vs 1540 ng · ml−1 · h). When comparing acidic and alkaline urinary pH conditions, half-life, Ae, CLR, and AUC were different. For a high fluid load the values at acidic vs alkaline pH were half-life 10.0 vs 15.7 h; Ae 15.9 vs 5.8 mg; CLR 288 vs 73 ml · min−1; AUC 976 vs 1480 ng · ml−1 · h. For a low fluid load the corresponding values at acidic vs alkaline pH were half-life 10.1 vs 16.0 h; Ae 15.9 vs 2.6 mg; CLR 267 vs 33 ml · min−1; AUC 1045 vs 1540 ng · ml−1 · h. It is concluded that urinary pH affects flecainide pharmacokinetics independently of urinary flow rate, and that a high flow enhances the elimination of flecainide only with an alkaline urine. This effect of flow rate does not appear to be of clinical relevance.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280108
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  • 32
    Digitale Medien
    Digitale Medien
    Kinetics of cholinesterase inhibition by eptastigmine in man (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 83-84 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Eptastigmine ; cholinesterase inhibitor ; Alzheimer's disease ; pharmacokinetics ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280116
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  • 33
    Digitale Medien
    Digitale Medien
    Pharmacokinetic investigation of oral and IV dihydroergotamine in healthy subjects (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 597-602 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Dihydroergotamine mesilate ; pharmacokinetics ; urinary excretion ; prolonged half-life ; deep compartment ; RIA ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A new radioimmunoassay (RIA) for the specific measurement of dihydroergotamine (DHE), sufficiently sensitive for the determination of low plasma concentrations, has been used to investigate the pharmacokinetics of unchanged DHE. In a randomized crossover trial, eight healthy male volunteers received single doses of DHE 5 mg, 10 mg and 20 mg orally and 0.1 mg and 0.5 mg intravenously. It was possible to determine plasma concentrations and urinary excretion of DHE over the following 48 h. A long terminal plasma elimination phase of unchanged DHE (half-life 15 h) was found. A similar terminal elimination half-life was also calculated from urine data. The multi-exponential decline in plasma DHE with a long terminal half-life suggests that distribution into a deep compartment contributes to the long-lasting effect of the drug. Plasma protein binding was 93%. Despite extensive tissue distribution (Vz=33 l/kg) and a high plasma clearance (CLP=2l/min), dose-independent linear pharmacokinetics was observed. The present assay was at least 20-times more specific than the polyvalent RIA used previously and appears suitable to explore the pharmacokinetics of unchanged DHE in patients on low-dose therapy. The long terminal elimination half-life of DHE only reported previously in studies using 3H-labelled drug, and considered to be due to metabolites, was also true for the parent compound. This, in addition to the sustained pharmacological activity of the 8′-hydroxy metabolite already shown, provides a further explanation for the long duration of action of DHE in animals and man.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314992
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  • 34
    Digitale Medien
    Digitale Medien
    Effect of piperine on bioavailability and pharmacokinetics of propranolol and theophylline in healthy volunteers (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 615-617 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Piperine ; Propranolol ; Theophylline ; pharmacokinetics ; drug interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The effect of piperine on the bioavailability and pharmacokinetics of propranolol and theophylline has been examined in a crossover study. Six subjects in each group received a single oral dose of propranolol 40 mg or theophylline (150 mg) alone or in combination with piperine 20 mg daily for 7 days. An earlier tmax and a higher Cmax and AUC were observed in the subjects who received piperine and propranolol. It produced a higher Cmax, longer elimination half-life and a higher AUC with theophylline. In clinical practice, the enhanced systemic availability of oral propranolol and theophylline could be exploited to achieve better therapeutic control and improved patient compliance.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314996
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  • 35
    Digitale Medien
    Digitale Medien
    Inhibition of ex-vivo PAF-induced platelet aggregation by the PAF-antagonist RP 48740: relationship to plasma concentrations in healthy volunteers (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 141-145 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Platelet activating ; Factor RP 48740 ; platelet aggregation ; PAF-antagonist ; dose-response relationship ; adverse effects ; pharmacokinetics ; dose-response relationship
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary RP 48740, 3-(3-pyridyl)-1H,3H-pyrrolo [1,2-c] thiazole-7-carboxamide, a specific competitive PAF-receptor antagonist in vitro, was given to 29 healthy male volunteers for 7 days. Plasma drug concentrations and exvivo PAF-induced platelet aggregation were assessed on Days 1, 4, and 7. RP 48740 had linear pharmacokinetics after single and repeated doses. It caused stable inhibition of PAF-induced platelet aggregation in a dose-dependent manner. The effect disappeared within 24 h, even after 7 days of repeated doses. The effect of RP 48740 displayed a sigmoidal relation to the plasma drug concentration; I50 2.3 (0.3) mg·l−1. There were no clinical or biological adverse reactions to RP 48740 during the study.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265907
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  • 36
    Digitale Medien
    Digitale Medien
    Enantioselective steady-state kinetics of unbound disopyramide and its dealkylated metabolite in man (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 481-484 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Disopyramide ; pharmacokinetics ; protein binding ; enantiomers ; metabolism ; metabolite kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Disopyramide is provided as a racemic mixture of R and S enantiomers, which have different pharmacodynamic and pharmacokinetic characteristics. Five volunteers were given racemic disopyramide 100 mg and 200 mg t.d.s. in a cross-over design. Plasma and urine concentrations of disopyramide and its active metabolite monodesisopropyl-disopyramide (MND) were determined at steady state by an enantioselective HPLC method. Unbound drug in plasma was measured after ultrafiltration. There was enantioselective clearance of unbound disopyramide (0.39 l.h−1.kg−1 for R-disopyramide and 0.58 l.h−1.kg−1 for S-disopyramide after 100 mg t.d.s.). The enantioselectivity was due to differences in the metabolism of disopyramide to MND and in further non-renal clearance, and the renal clearance of disopyramide was not enantioselective. The in vivo protein binding of disopyramide, which was saturable for both enantiomers, was also enantioselective. The difference in binding of the two enantiomers was explained by a difference in apparent binding capacity rather than in apparent binding affinity. The renal clearance of S-MND was significantly higher than R-MND (0.29 and 0.19 l.h−1.kg−1, respectively, after 100 mg t.d.s.). The renal clearance of MND also showed a tendency to saturation at higher concentrations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00626374
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  • 37
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of oral salbutamol controlled-release in Asian patients with asthma (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 495-496 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Asthma ; Salbutamol ; Asians ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Using a double blind, double dummy crossover design, single dose and steady state pharmacokinetics of oral controlled release (SCR) salbutamol 4 mg and 8 mg tablets b. d. has been studied in 8 Asian patients. Plasma salbutamol was measured over 12 h. In 8 patients the single dose mean Cmax was 4.2 ng·ml−1 and 7.7 ng·ml−1 after 4 and 8 mg, respectively. In 5 patients the steady state mean Cmax, Cmin and tmax were 8.1 ng·ml−1 and 4.7 ng·ml−1 and 6 h for the 4 mg tablets and 14.1 ng·ml−1 and 7.1 ng·ml−1 and 4 h for the 8 mg tablets. It is concluded that both doses of SCR show features of controlled release and that they produced a relatively constant plasma level of salbutamol in Asian patients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00626378
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  • 38
    Digitale Medien
    Digitale Medien
    Relation between plasma concentration and clinical efficacy after sublingual single dose apomorphine in Parkinson's disease (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 493-494 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Parkinson's disease ; Apomorphine ; pharmacokinetics ; adverse effect ; on-off effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Five patients with Parkinson's disease were given a single sublingual dose of apomorphine in 3 mg tablets (2 patients received 18 mg and 3 patients took 39 mg). The therapeutic effect appeared within 33.0 min and lasted 137 min. There was a significant correlation between peak concentration, area under the curve, dose (mg/kg) and the duration of the therapeutic effect.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00626377
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  • 39
    Digitale Medien
    Digitale Medien
    Therapeutic monitoring of cyclosporin — an update (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 273-283 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Cyclosporin A ; therapeutic monitoring ; assay techniques ; pharmacokinetics ; dose-response relationships
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The success of organ transplantation is closely related to clinical use of the immunosuppressive drug cyclosporin (CsA). The dosage of CsA is complicated by the large intra- and interindividual variability in its pharmacokinetics, as well as by the narrow concentration range between insufficient immunosuppression and toxicity. Potential sources of error in the sampling procedure and the advantages and disadvantages of the available analytical methods are discussed. Traditionally, 12 or 24 hour trough concentrations of CsA are monitored. Recently, peak concentrations or estimation of AUCs by a limited sampling strategy have been tried to improve the relatively weak concentration-effect and concentration-toxicity relationships found with trough CsA concentration monitoring. Studies of the CsA concentration-effect relationships for various treatment indications are reviewed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314952
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  • 40
    Digitale Medien
    Digitale Medien
    Verapamil in the prophylaxis of bronchial asthma (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 317-319 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Asthma ; Verapamil ; histamine-induced bronchoconstriction ; calcium antagonists ; plasma levels ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A single oral dose of verapamil 80 mg was shown significantly to inhibit histamine-induced bronchoconstriction in 8 out of 16 asthmatic subjects (maximum increase in PD20FEVHi 416%). There was still significant protection (Δ PD20FEV1Hi〉100%) in the responders 5 h after the oral dose. The relationship of the bronchoprotective effect to the plasma level of verapamil was also examined. Responders and non-responders did not differ significantly in the peak plasma level or the time course of the plasma verapamil concentration. The protective effect was not correlated with the peak plasma level of verapamil or with the baseline bronchial hyperreactivity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314959
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  • 41
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of paroxetine in patients with cirrhosis (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 351-354 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Paroxetine ; Cirrhosis ; pharmacokinetics ; multiple-dose study ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In a 14-day multiple-dose study the pharmacokinetics of paroxetine was investigated in 12 patients with alcoholic cirrhosis and in 6 subjects without liver disease. The dose of 20–30 mg paroxetine daily was adjusted to the reduction in liver function, as assessed by the galactose elimination capacity. Accordingly, all but two of the cirrhotic patients received 20 mg, while all six control subjects received 30 mg. Dose-corrected, trough drug concentration at steady state (CSS min) and dose-corrected AUC24h were significantly higher in the patients with liver diseases than in the control subjects [3.4 vs 1.5 ng · ml−1 per mg paroxetine and 89 vs 43 h (ng) · ml−1 per mg paroxetine]. The elimination t1/2 was prolonged [83 vs 36 h], but the difference was not statistically significant, and the cirrhotic patients were still able to clear almost all the paroxetine by metabolism. All but two patients with cirrhosis experienced nausea during the first two or three days after the first dose, while none of the controls had this symptom. The study showed slower elimination of paroxetine and consequently higher plasma levels in patients with cirrhosis, suggesting that in the latter the dose of paroxetine should be in the lower end of the therapeutic range.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314966
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  • 42
    Digitale Medien
    Digitale Medien
    Dose-dependent pharmacokinetics of benzoic acid following oral administration of sodium benzoate to humans (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 363-368 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Benzoic acid ; hippuric acid ; pharmacokinetics ; hyperammonaemia ; ureagenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Plasma concentration-time data for benzoic and hippuric acids and urinary excretion-time data for hippuric acid were analyzed simultaneously after oral doses of 40, 80 or 160 mg/kg sodium benzoate administered at least one week apart to 6 healthy subjects. The mean AUCs of benzoic acid after the doses of 80 and 160 mg/kg of sodium benzoate were 3.7- and 12.0-times greater, respectively, than after 40 mg/kg. However, the mean AUC of hippuric acid was roughly proportional to the benzoate doses. The observed data were explained by a one-compartment model with first-order rate absorption and Michaelis-Menten elimination of benzoic acid, together with a one-compartment model with first-order elimination for hippuric acid. Although the maximum rate of biotransformation of benzoic acid to hippuric acid varied between 17.2 and 28.8 mg·kg−1·h−1 among the six individuals, the mean value (23.0 mg·kg−1·h−1) was fairly close to that provided by daily maximum dose (0.5 g·kg−1·day−1) recommended in the treatment of hyperammonaemia in patients with inborn errors of ureagenesis. The individual maximum rate of metabolism can be estimated from the urinary excretion rate of hippuric acid 1.5 to 3 h after the single oral dose of 80 to 160 mg·kg−1 sodium benzoate. The justification of this concept requires further studies in patients with inborn errors of urea synthesis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314969
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  • 43
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of intramuscular nicomorphine and its metabolites in man (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 375-378 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Nicomorphine ; 6-nicotinoylmorphine ; morphine ; intramuscular administration ; metabolism ; absorption ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary After i.m. injection nicomorphine is relatively slowly absorbed from the muscular depot and is found in the serum for approximately 1 h. The rate of absorption differs between patients and governs the overall pharmacokinetic profile of the compound. The relative AUCs were nicomorphine 18%, 6-nicotinoylmorphine 17%, and morphine 65%. Nicomorphine and 6-nicotinoylmorphine have significantly higher AUCs after i.m. injection than after i.v. injection, while the AUC of morphine and the total AUC show no difference between the two modes of administration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314971
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  • 44
    Digitale Medien
    Digitale Medien
    Decreased and variable systemic availability of zidovudine in patients with AIDS if administered with a meal (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 305-308 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Zidovudine ; acquired immunodeficiency syndrome (AIDS) ; pharmacokinetics ; bioavailability ; food intake
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The systemic availability of oral zidovudine has been studied in 13 patients with the acquired immunodeficiency syndrome (AIDS) dosed either fasting or with breakfast. The mean peak plasma concentration and AUC of zidovudine were significantly 2.8- and 1.4-times higher in fasting patients than in those treated during meal. In both conditions the mean half-life was about 1.5 h and the period of plasma zidovudine concentrations 〉1 μmol · l−1 was 2 h (NS). It is concluded that if zidovudine is taken on an empty stomach, high peak plasma concentrations and decreased variation in pharmacological parameters may be expected. Whether or not this will influence toxicity and efficacy remains to be shown.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315215
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  • 45
    Digitale Medien
    Digitale Medien
    Absorption of theophylline from a new theophylline controlled-release capsule (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 319-320 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Theophylline ; controlled-release formulation ; absorption ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315219
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  • 46
    Digitale Medien
    Digitale Medien
    Diuretic effect and disposition of furosemide in cystic fibrosis (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 333-341 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Furosemide ; cystic fibrosis ; pharmacokinetics ; diuretic effect ; baseline urine flow
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacodynamics and kinetics of single oral and intravenous doses of furosemide were studied in 9 patients (mean age 18.5 y) with cystic fibrosis. The diuretic effect of furosemide lasted for 6 h after oral administration and 2 h following intravenous injection of the drug. The patients with cystic fibrosis had a more pronounced diuretic response both to the oral and intravenous treatments than that reported in normals. Furosemide caused a marked decrease in urine pH for 5 h following the oral dose and between the 2nd and 3rd h after i.v. injection. The baseline nocturnal urine flow rate in 7 of the 9 patients given furosemide orally was increased by 30.6% compared to that reported in healthy subjects. The bioavailability of furosemide, its mean absorption rate and the mean plasma and urinary elimination half-lives both of the oral and the intravenous drug were similar to those reported in normal subjects. The patients with cystic fibrosis showed, however, about double normal mean total clearance after both the oral and i.v. treatments, and its renal clearance was almost half the plasma clearance. Nonrenal clearance was markedly increased in the patients, which agreed with a considerable decrease in the renal excretion of the drug. The mean apparent volume of distribution was also markedly increased compared to data in the literature. Oral furosemide resulted in a moderate increase in haematocrit and haemoglobin levels in 7 of 9 patients with cystic fibrosis and marked hypokalemia developed in 6 of the 9 patients 6 h after dosing. Pulmonary function tests performed at that time were changed in an inconsistent manner. The sweat test was significantly perturbed in those subjects, although the concentration of chloride in sweat did not fall below 60 mEq/l in any of the sweat samples tested.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265840
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  • 47
    Digitale Medien
    Digitale Medien
    The pharmacokinetics and pharmacodynamics of lisuride in healthy volunteers after intravenous, intramuscular, and subcutaneous injection (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 399-403 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Lisuride ; pharmacokinetics ; prolactin concentrations ; healthy volunteers ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The plasma concentration of lisuride and prolactin have been measured in twelve healthy male volunteers after IV, IM or SC injection of 25 μg lisuride hydrogen maleate as an aqueous solution. After IV administration the plasma lisuride fell in two phases with half-lives of 14 min and 1.5 h. Total clearance was 13 ml·min−1·kg−1. After IM and SC injection the plasma concentrations peaked at 12 to 15 min and the profiles were similar to that found after IV administration. The systemic availabilities were 90% and 94%, respectively. Prolactin concentrations were reduced by a maximum of 60% relative to the normal circadian rhythm after all three routes of administration. The treatments were well tolerated, the only adverse reactions reported by some of the volunteers being mild, transient dizziness, tiredness, and nausea.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265851
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  • 48
    Digitale Medien
    Digitale Medien
    Disposition of oral quinine in acute falciparum malaria (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 49-52 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Quinine ; pharmacokinetics ; falciparum malaria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Plasma quinine concentrations following oral quinine sulphate 10 mg salt/kg have been measured by HPLC in 15 adult Thai patients with uncomplicated falciparum malaria. In 10 of the same patients the study was repeated in convalescence. In acute malaria plasma concentrations were approximately 50% higher than in convalescence; the mean acute peak plasma quinine concentration was 8.4 mg·l−1 compared to 5.7 mg·l−1 in convalescence. There was considerable variation in the rate of drug absorption, particularly in acute malaria. The mean time to peak plasma concentration was 5.9 h in acute malaria and 3.2 h in convalescence. The apparent clearance of oral quinine (CL/f) during the illness was 1.51 ml·kg−1·min−1, which was significantly lower than in convalescence — 2.67 ml·kg−·min−1. Estimated free quinine clearance was also lower in the acute phase: 30.6 compared to 49.0 ml·kg−1·min−1 in convalescence. Mean (SD) plasma protein binding of quinine was 94.7% in acute malaria and 92.8% in convalescence. Binding was significantly correlated with the plasma concentration of α1 acid glycoprotein (r=0.5), which was significantly higher in the acute phase; 1.48 g·l−1 compared to 1.05 g·l−1 during convalescence. Oral quinine sulphate was well absorbed in uncomplicated falciparum malaria. High blood concentrations following the administration of oral quinine in acute malaria are probably related to increased plasma protein binding, lower apparent volume of distribution, and a reduction in its systemic clearance.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315138
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  • 49
    Digitale Medien
    Digitale Medien
    Lack of effect of omeprazole treatment on steady-state plasma levels of metoprolol (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 61-65 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Omeprazole ; substituted benzimidazole ; metoprolol ; interaction ; cytochrome P450 ; debrisoquine hydroxylase ; pharmacokinetics ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In a randomised double-blind crossover study, seven healthy males were concomitantly given metoprolol 100 mg o. d. as a controlled release formulation, and omeprazole 40 mg o. d. or placebo, for 8 days. Plasma levels of the R- and S-enantiomers of metoprolol were determined on the 8th day of each treatment. The subjects were also characterised by their metabolic capacity to hydroxylate debrisoquine. Concomitant omeprazole treatment had no significant influence on the steady-state plasma levels of the two enantiomers of metoprolol. All subjects were characterised by extensive debrisoquine hydroxylation, i.e. extensive metoprolol metabolism. As metoprolol is metabolised to a great extent by debrisoquine hydroxylase (IID6), it is concluded that concomitant omeprazole treatment will probably have a negligible influence on the metabolism of the relatively large number of drugs mainly metabolised by this isoenzyme of the cytochrome P450 family.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315140
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  • 50
    Digitale Medien
    Digitale Medien
    Is there a need for more precise definitions of bioavailability? (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 123-126 
    Details
    ISSN: 1432-1041
    Schlagwort(e): bioavailability definition ; health authorities ; pharmacokinetics ; drug registration Participants: L. P. Balant (Geneva, Switzerland), L. Z. Benet (San Francisco, USA), H. Blume (Eschborn, FRG), G. Bozler (Biberach, FRG), D. D. Breimer (Leiden, The Netherlands), M. Eichelbaum (Stuttgart, FRG), U. Gundert-Remy (Berlin, FRG), J. L. Hirtz (Paris, France), E. Mutschler (Frankfurt, FRG), K. K. Midha (Saskatoon, Canada), A. G. Rauws (Bilthoven, The Netherlands), W. A. Ritschel (Cincinnati, USA), L. N. Sansom (Adelaide, Australia), J. P. Skelly (Rockville, USA), and K.-O. Vollmer (Freiburg, FRG)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary After evaluation of the present definitions in a set of particular cases, it was agreed that there was no need for “more precise” definitions and that the current ones were adequate in the majority of cases. However, it was felt that the present definitions might be improved, in particular in view of the existence of non-systemically acting drugs and future “targeted drugs”. Thus, the FDA definition might be modified as follows: “Bioavailability means the rate and extent to which the active drug ingredient or therapeutic moiety from a drug product becomes available at the site of drug action or in a biological medium believed to reflect accessibility to a site of action”.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280064
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  • 51
    Digitale Medien
    Digitale Medien
    Changes in gentamicin pharmacokinetic profiles induced by mechanical ventilation (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 297-302 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Gentamicin ; pharmacokinetics ; mechanical ventilation ; therapeutic dose range
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The influence of controlled mechanical ventilation (CMV) on the pharmacokinetic profile of gentamicin has been examined in 23 patients after elective open heart surgery. A parallel design was adopted in two groups of patients: 13 patients requiring CMV for at least 32 h after surgery, all of whom were able to breath spontaneously (SB) after 72 h (study group), and 10 patients who required CMV for only a brief period and who showed SB at 32 h postsurgery. Haemodynamic parameters remained stable throughout the study. Apparent volume of distribution (Vz), half-life (t1/2), total clearance (CL), peak (C max ss ) and trough (C min ss ) plasma levels at steady-state for target levels (6–8 μg/ml), were measured. In the study group significant differences between CMV and SB conditions were found in Vz (mean 0.36 and 0.25 l/kg), t1/2 (mean 3.63 and 2.90 h) and C max ss (mean 4.30 and 5.53 μg/ml) while C min ss (mean 1.06 μg·ml−1 and 0.92 μg·ml−1) did not change significantly. In contrast, the pharmacokinetics in the control group showed no differences. It appears that CMV leads to an increase in gentamicin Vz, which accounts for the fall in C max ss below the therapeutic dose range (〈5 μg/ml) recommended for gentamicin. It seems advisable to use a larger dose of gentamicin in patients receiving CMV, even before the level is assessed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315213
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  • 52
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of intravenous and oral chlordesmethyldiazepam in patients on regular haemodialysis (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 65-68 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Chlordesmethyldiazepam ; pharmacokinetics ; i.v./p.o. administration ; renal failure ; protein binding ; pharmacodynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of a single 2 mg IV dose of chlordesmethyldiazepam has been studied in 11 patients with renal failure on regular haemodialysis and in 11 age-matched healthy controls. The kinetics was also examined after a single 2 mg oral dose in 6 of the 11 renal failure patients. After intravenous administration the kinetics of total chlordesmethyldiazepam in renal patients and controls were the same. The unbound fraction of the drug in renal patients was higher (5.5%) than in controls (2.9%). Correction for differences in protein binding revealed a reduced apparent volume of distribution (47 vs. 140 l · kg−1) and a reduced clearance (5.0 vs. 10.5 ml · min−1 · kg−1) in the patients. The systemic availability of oral chlordesmethyldiazepam was good (82%) despite a relatively slow absorption rate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280109
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  • 53
    Digitale Medien
    Digitale Medien
    Response to furosemide during dehydration with and without naproxen pretreatment of kidney donors and renal transplant recipients (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 209-214 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Furosemide ; renal transplant recipients ; kidney donors ; naproxen ; dehydration ; pharmacokinetics ; salt-regulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The response to 40 mg furosemide p.o. in 6 healthy kidney donors and 6 renal transplant recipients with and without naproxen pretreatment has been studied. No volume replacement was given in order to study the development of tolerance. The subjects showed an average dehydration of 1.5 kg · 6 h−1. While mean creatinine clearance was equal in patients and donors (76 vs 80 ml/min), renal furosemide clearance was significantly lower in the patients (47 vs 81 ml/min; P〈0.05). The patients also excreted a smaller fraction of the dose in the urine (5.7 vs 7.8 mg/6 h; P〈0.05). As the overall renal sensitivity was similar in the two groups, the natriuretic response was correspondingly smaller in transplant recipients as compared to donors. Within the observation period of 6 h after dosing, acute tolerance developed in the donors and in 4 of the 6 patients, as shown by clockwise hysteresis in the dose (urine furosemide excretion rate)-response (natriuresis) curves. Pretreatment with naproxen reduced renal sensitivity to furosemide (right shift of the dose response curve) in all the donors but in only 2 of the patients. In both groups acute tolerance was less pronounced after naproxen, which may indicate involvement of the prostaglandin system in the development of acute tolerance. The results may also indicate regeneration of sympathetic nerves with functional capacity in at least some renal transplants, or that other mechanisms of salt regulation compensate for loss of sympathetic nerve activity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315197
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  • 54
    Digitale Medien
    Digitale Medien
    Monitoring of the free concentration of cyclosporine in plasma in man (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 571-575 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Cyclosporine ; free drug in plasma ; therapeutic drug monitoring ; renal transplantation ; plasma binding ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The free fraction of cyclosporine A (CsA) and its total plasma concentration as determined by HPLC(CsAT) were prospectively monitored in 66 recipients of renal transplants. The free CsA levels (CsAu) were calculated. The variability in free CsA levels was no less than for total CsAT levels. The correlation between CsAu and CsAT was high (r=0.90). Both CsAT and CsAu covaried with serum triglycerides and apolipoprotein A1. Fourty-four of the 66 patients suffered acute rejection episodes on 69 occasions. CsAT and CSAu both decreased and to a similar extent at the occurrence of acute rejection (42% and 59% decrease, respectively; significant vs baseline. Notsignificant difference in decrease in CsATvsCsAu). Acute nephrotoxicity occurred on 11 occasions in 10 patients. Both CsAT and CSAu were approximately twice as high at the time of acute nephrotoxicity as compared to one week previously. Both CsAT and CsAu were higher during the first month after transplantation in patients with than in patients without systemic infection. Thus, plasma CsAu gave no additional clinical information or guidance compared to CsAT in renal transplant recipients. Due to the complexity of its assay, which requires two consecutive analyses, there does not appear to be any need for routine monitoring of CsAu in renal transplant recipients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00279972
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  • 55
    Digitale Medien
    Digitale Medien
    Flecainide: evidence of non-linear kinetics (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 57-59 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Flecainide ; pharmacokinetics ; ventricular arrhythmias
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of flecainide has been studied in 12 patients with ventricular arrhythmias, both after single administration and during chronic treatment. Both the half-life and the AUC were significantly increased during chronic treatment. This suggests that the kinetics of flecainide might be non-linear also in patients with normal kidney and liver function. The increase in plasma flecainide levels during chronic treatment could not be predicted, so close monitoring of its plasma levels is advisable.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280107
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  • 56
    Digitale Medien
    Digitale Medien
    Pharmacokinetic profile and tolerability of pimobendan in patients with terminal renal insufficiency (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 107-111 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Pimobendan ; pharmacokinetics ; tolerability ; renal impairment ; adverse effects ; haemodynamic actions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of an i.v. bolus of pimobendan (P) 2.5 mg and 5.0 mg, its tolerability and the effect on heart rate and blood pressure have been studied in 12 subjects (42–70 y) suffering from severe terminal renal impairment. Plasma level data were compared with those obtained in a previous investigation in healthy volunteers. Pharmacokinetics were dose linear and were comparable to those in healthy subjects. No adjustment of the dose of P is necessary in patients with severe renal impairment. Tolerability of P, observed by means of blood pressure monitoring, clinical chemistry tests, electrocardiography and subjective judgement resulted in 4 complaints out of 12 patients: three suffered from orthostatic problems and vomiting, and one patient had nausea. Mean heart rate was elevated by 19% (2.5 mg) and 16% (5.0 mg). Blood pressure was significantly reduced after 2.5 mg P (23% systolic and 26% diastolic pressure), and after 5.0 mg P by 25% systolic and 23% diastolic pressure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315148
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  • 57
    Digitale Medien
    Digitale Medien
    Clinical pharmacokinetics of 3-day continuous infusion cisplatin and daily bolus 5-Fluorouracil (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 115-117 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Cisplatin ; 5-Fluorouracil ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315150
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  • 58
    Digitale Medien
    Digitale Medien
    Continuous infusion of high-dose metoclopramide: comparison of pharmacokinetically adjusted and standard doses for the control of cisplatin-induced acute emesis (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 283-286 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Metoclopramide cancer chemotherapy ; emesis ; continuous infusion ; pharmacokinetics ; cisplatin ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Metoclopramide was administered by continuous infusion to two groups each of 14 patients on chemotherapy, randomized to receive either doses adjusted to individual pharmacokinetic parameters or doses adjusted as usual to body weight. The mean plasma concentration at the end of the infusion in the adjusted group was 1.01 mg · 1−1, close to that aimed for (1.20 mg · 1−1). It was significantly different from that in the other group, v0.54 mg · 1−1. Antiemetic efficacy, defined as ⩽2 emetic events in the 24 h following cisplatin, was similar in both groups (being found in 12/14 (86%) and 10/14 patients (71%), respectively). Analysis of the cumulative percentage of responders according to plasma concentration showed a clear plasma concentration-effect relationship. Routine MCP pharmacokinetic dosage adjustment is not indicated, but this therapeutic approach can be used to optimize antiemetic therapy in poor responder patients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315210
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  • 59
    Digitale Medien
    Digitale Medien
    Cyclosporine pharmacokinetics in liver transplant recipients: evaluation of results using both polyclonal radioimmunoassay and liquid chromatographic analysis (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 513-519 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Cyclosporine ; liver transplant recipients ; radioimmunoassay ; pharmacokinetics ; bioavailability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Pharmacokinetic variables were derived from cyclosporine measurements using liquid chromatography (HPLC) and radioimmunoassay with a non-selective polyclonal antibody (PARIA) in 11 orthotopic liver transplant recipients studied in paired oral and intravenous studies both before and after permanent clamping of the biliary T-tube. After oral drug administration, mean areas under blood cyclosporine concentration versus time curves before clamping were around 5.2-fold greater by PARIA than HPLC but 2.9-fold greater after clamping and closer to comparable values after intravenous cyclosporine (2.5 and 2.3-fold, respectively). Cyclosporine clearance was smaller by PARIA than HPLC (mean 7.3 versus 3.3 ml · min−1 · kg−1, respectively, before clamping). Both values decreased by 25% after clamping (to 5.5 and 2.4 ml · min−1 · kg−1, respectively), although there was no significant change in distribution or elimination half-lives (around 0.5 and 8 h, respectively). The mean bioavailability of oral cyclosporine increased significantly after clamping in 9 patients (from 10.6% to 28.1% by HPLC and from 14.8 to 35.1% by PARIA) but in two patients who developed the vanishing bile duct syndrome values fell to 〈 10% and the proportional overestimation of cyclosporine concentrations by PARIA increased. Clamping had no significant effect on the mean apparent volumes of distribution but values of Vz were approximately twice those of Vss (around 2.6 and 1.3 l · kg−1 by PARIA and HPLC respectively). Mean half lives after clamping were shorter following oral than intravenous cyclosporine (t1/2λ2 around 15 h enterally versus 8 h parenterally). These data suggest delays in cyclosporine absorption and significant first pass metabolism which may contribute to higher PARIA:HPLC ratios after oral dosing and to reduced bioavailability before clamping.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00315232
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  • 60
    Digitale Medien
    Digitale Medien
    Single-dose and steady-state kinetics of morphine and its metabolites in cancer patients — a comparison of two oral formulations (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 585-591 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Morphine ; metabolites ; clinical trial ; pharmacokinetics ; controlled release formulation ; cancer patients ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The single-dose and steady state kinetics of morphine given as controlled-release tablets (30 mg every 12 h) and as a solution (15 mg every 6 h) have been compared in 11 cancer patients with chronic pain. The concentrations of morphine, morphine-3-glucuronide (M3G), and morphine-6-glucuronide (M6G) were analyzed by HPLC. There were no significant differences between the tablets and solution in the mean steady state concentrations of morphine, M3G or M6G. The tmax was 3.3 h for the tablets compared to 1.1 h for the solution. After giving the controlled-release tablets every 12 h there was a significantly higher fluctuation index of the morphine concentrations than after the solution. Urinary recovery at steady state was comparable between the two preparations, with averages of 57% and 47%, respectively. Thus, no major differences were found in the pharmacokinetics of morphine and its glucuronidated metabolites after 30 mg morphine as controlled-release tablets every 12 h or 15 mg of morphine solution every 6 h, except for a significantly longer tmax and greater fluctuation in morphine concentrations after the controlled-release tablets.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00279975
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  • 61
    Digitale Medien
    Digitale Medien
    Sublingual captopril — a pharmacokinetic and pharmacodynamic evaluation (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 393-398 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Captopril ; sublingual ; pharmacokinetics ; pharmacodynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In this study we compared the pharmacokinetics and pharmacodynamics of captopril after sublingual and peroral administration. Single 25 mg doses of captopril were administered sublingually and perorally on two different occasions in a randomised cross-over fashion to eight healthy volunteers aged 22–35 years. The kinetics of unchanged captopril, plasma renin activity (PRA), BP and heart rate were studied over three hours after both peroral and sublingual administration of captopril. Mean pharmacokinetic parameters for unchanged captopril after sublingual administration were: Cmax, 234 ng·ml−1; tmax, 45 min; AUC (0–3 h), 15.1 μg·ml−1. min. Mean pharmacokinetic parameters for unchanged captopril after peroral administration were: Cmax, 228 ng·ml−1; tmax, 75 min; AUC (0–3 h), 17.0 μg·ml−1. min. tmax was significantly shorter when captopril was administered sublingually; all other pharmacokinetic parameters were equivalent. The plasma captopril concentrations achieved post drug administration led to increases in PRA and reductions in BP. tmax for PRA was 86 min for sublingual captopril and 113 min for perorally administered drug. Peak PRA values were, however, not significantly different. BP, as expected, was not reduced dramatically in these healthy volunteer subjects, however, in systolic BP vs time profiles, BP was significantly lower after volunteers received sublingual captopril. Heart rate increased slightly after captopril administration; there were no differences between the two routes of administration. Administration of captopril sublingually, therefore led to a more rapid attainment of plasma captopril concentrations and had a more rapid onset of pharmacological effect when compared with peroral administration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265850
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  • 62
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of SUN 1165, a new antiarrhythmic agent, in renal dysfunction (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 411-414 
    Details
    ISSN: 1432-1041
    Schlagwort(e): SUN 1165 ; renal failure ; antiarrhythmic agent ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of a new Class I antiarrhythmic agent, SUN 1165, has been studied in 32 patients with varying degrees of renal impairment following a single oral dose of 50 mg. The apparent volume of distribution at steady state was 1.48 1 · kg−1, the absorption rate constant was 2.2 h−1, and plasma protein binding was 26.8% in subjects with normal renal function. These variables were not altered with renal impairment. More than 60% of SUN 1165 given orally was excreted unchanged via the kidney, both by tubular secretion and glomerular filtration. The elimination rate constant, the apparent total body clearance and the apparent renal clearance were linearly correlated with the endogenous creatinine clearance. The half-time of elimination was 3.4 h in normal subjects and it was prolonged to 23.7 h in severe renal failure (creatinine clearance below 20 ml · min−1 · 1.48 m−2). Dosage adjustment of SUN 1165 is necessary in renal failure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265853
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  • 63
    Digitale Medien
    Digitale Medien
    Cyclopentenyl cytosine: Interspecies predictions based on rodent plasma and urine kinetics (1991)
    Springer
    Investigational new drugs 9 (1991), S. 9-17 
    Details
    ISSN: 1573-0646
    Schlagwort(e): cyclopentenyl cytosine ; interspecies ; pharmacokinetics ; toxicity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A hybrid compartmental-physiological model for cyclopentenyl cytosine (CPE-C) is designed on the basis of early limited rodent pharmacokinetic data. Application of model independent pharmacokinetics and biochemical knowledge was first used to conceptualize such a model. The approach was to scale the physiological parameters of the model (compartmental clearances) and keep constant the anatomic parameters of the model (compartment volumes). Scaling of physiological mechanisms was based on body weight/surface area ratios. Using these principles, simulations with the model can reasonably anticipate the in vivo behavior of (CPE-C) in several species (mouse, rat, dog). The model is useful in understanding species differences in pharmacokinetic behavior of CPE-C.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00194539
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  • 64
    Digitale Medien
    Digitale Medien
    Ifosfamide pharmacokinetics (1991)
    Springer
    Investigational new drugs 9 (1991), S. 305-311 
    Details
    ISSN: 1573-0646
    Schlagwort(e): ifosfamide ; pharmacokinetics ; review
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract This review examines and details the pharmacokinetics of ifosfamide (a congener of cyclophosphamide) when administered by a number of commonly used chemotherapeutic regimes. The influence of route of administration, schedule of administration and dose on the pharmacokinetics of ifosfamide and its metabolites are discussed. Oral fractionated ifosfamide therapy, which causes an excessively high incidence of neurotoxicity, is similar to intravenous fractionated therapy in that it exhibits a time dependent increase in ifosfamide metabolic clearance. Five g/m2 ifosfamide given intravenously as a short (half hour) or long (24 hr) infusion does not exhibit dose dependent (zero-order) pharmacokinetics. In patients who develop ifosfamide/mesna associated CNS toxicity the pharmacokinetics of parent ifosfamide are not aberrant. This implies that ifosfamide metabolites are more likely to be responsible for the neurotoxicity rather than the parent drug. The development of simple and more specific analytical methodology, will allow further studies of the pharmacokinetics of the active ifosfamide metabolite(s). This may lead to further optimisation of the therapeutic index of ifosfamide treatment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00183570
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  • 65
    Digitale Medien
    Digitale Medien
    The pharmacokinetics of aspirin in rats and the effect of buffer (1991)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 19 (1991), S. 157-173 
    Details
    ISSN: 1573-8744
    Schlagwort(e): aspirin ; rat ; pharmacokinetics ; effect of buffer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Aspirin (acetylsalicyclic add) was administered to rats intravenously, orally, and intraintestinally at different doses or in different dosage forms. The distribution and elimination kinetics of aspirin in rats following intravenous administration were best described by a two-compartmental open system and were dose independent up to 15 mg/kg. The terminal elimination half-life following intravenous dosing (10 mg/kg) was 3.36±0.85min (n=15) with the clearance being 8.40±1.24 L/(kg.hr). Intravenous distribution and elimination kinetics of aspirin in rats were not influenced by an orally administered buffered solution with a buffer capacity of 0.933 mEq ANC (acid neutralizing capacity) per kg of body weight. However, this orally buffered solution did change the gastrointestinal absorption kinetics of aspirin in rats. The absolute bioavailable dose of aspirin was 56.6±10.4% (n=6)following its administration in an unbuffered solution while it was only 31.8±8.0% (n=6)following administration in the buffered solution. The corresponding values of the absolute bioavailable doses were 43.4±3.7% and 25.5±1.8% following intraintestinal administration. The lower systemic availability of aspirin in the presence of buffer is attributed to a greater fraction of the administered dose becoming available for absorption from the intestine where the extraction efficiency is higher than that in the stomach.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01073867
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  • 66
    Digitale Medien
    Digitale Medien
    Pharmacokinetics and bioavailability of diclofenac in the rat (1991)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 19 (1991), S. 647-665 
    Details
    ISSN: 1573-8744
    Schlagwort(e): diclofenac sodium ; biliary excretion ; pharmacokinetics ; bioavailability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Diclofenac sodium is a widely used drug with interesting absorption and disposition features when administered to laboratory animals. The present study was undertaken to assess the pharmacokinetics of the drug after iv and gastrointestinal dosing to rats. Renal excretion of unchanged drug was negligible, but biliary excretion of the drug (unchanged and conjugated) was detected in bile duct-cannulated rats; it accounted for 27.2 and 31.2% of the total dose following iv and intraduodenal administration, respectively. Most of the drug excreted in the bile was conjugated diclofenac; unchanged drug accounted for only 4.7 and 5.4% of total diclofenac excreted in the bile after iv and intraduodenal dosing, respectively. In normal animals, intestinal absorption of the drug excreted in the bile resulted in higher drug concentrations in plasma than those obtained in bile duct-cannulated rats, but only after 60 min of dosing. When administered directly into the duodenum, diclofenac absorption was extremely fast and the maximum plasma diclofenac concentration was reached within 2 min. After oral dosing, an early peak was also observed, but it was lower than that obtained after intraduodenal dosing: 71% diclofenac hioavailability was found in bile duct-cannulated rats intraduodenally dosed, whereas in normal animals dosed by mouth a bioavailability of 79% was obtained. In normal animals intraduodenally dosed, an apparent bioavailability of 106% was observed. All of these features, particularly the influence of enterohepatic circulation on drug bioavailability, are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01080872
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  • 67
    Digitale Medien
    Digitale Medien
    Semiparametric analysis of non-steady-state pharmacodynamic data (1991)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 19 (1991), S. 691-712 
    Details
    ISSN: 1573-8744
    Schlagwort(e): pharmacokinetics ; pharmacodynamics ; linear system analysis ; nonlinear system analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract We present an approach to the analysis of pharmacodynamic (PD) data arising from non-steadystate experiments, meant to be used when only PD data, not pharmacokinetic (PK) data, are available. The approach allows estimation of the steady-state relationship between drug input and effect. The analysis is based on a model describing the time dependence of drug effect (E) on (unobserved) drug concentration (Ce) in an hypothetical effect compartment. The model consists of (i) a known model for the input rate of drug I(t), (ii) a parametric model; L(t, a) (a function of time t, and vector of parameters a), relating I to an observed variable X, (iii) a nonparametric model relating X to E. Ce is proportional to X. X(t) is given by I(X) * L(t, a)/AL, where L(t,α)=e −α 1 t * ∑ k=1 m , α2k e −α 2k+1 t, ∑ k=1 m α2k=1, AL=∫ 0 ∞ L(t) dt, and * indicates convolution.The nonparametric model relating X to Eis a cubic spline, a function of X and a vector of (linear) parameters β. The values of α and β are chosen to minimize the sum of squared residuals between predicted and observed E. We also describe a similar model, generalizing a previously described one, to analyze PK/PD data. Applications of the approach to different drug-effect relationships (verapamil-PR interval, hydroxazine-wheal and flare, flecainide and/or verapamil-PR, and left ventricular ejection fraction) are reported.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01080874
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  • 68
    Digitale Medien
    Digitale Medien
    Gossypol pharmacokinetics in mid-lactation Brown swiss dairy cows (1991)
    Springer
    Veterinary research communications 15 (1991), S. 379-385 
    Details
    ISSN: 1573-7446
    Schlagwort(e): cattle ; dairy cow ; gossypol ; pharmacokinetics ; serum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract A bolus equivalent to 450 ppm (dosage based on average feed intake for lactating dairy cows of similar mass) of gossypol was administered orally to three Brown Swiss dairy cows in mid lactation daily for a 7-day treatment period. Blood samples were taken daily during a 2-day pretreatment period, the 7-day treatment period and a 6-day recovery period. The serum recovered from the cows was stored at -20°C until analysis for extractable gossypol content. The highest concentration of gossypol (a mean of 0.53 μg/ml serum) was attained in all the cows on day 6 of the treatment period, indicating that a steady-state condition had been reached before the end of the treatment period. The gossypol concentrations then gradually declined during the 6-day recovery period but never fell to the zero baseline. The cows exhibited terminal elimination half-lives of 67, 67.5 and 40 h. Gossypol elimination was best described by a bi-exponential decay curve in two cows and a mono-exponential decay curve in the remaining cow.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00366995
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  • 69
    Digitale Medien
    Digitale Medien
    An approximate model-independent method to maintain constant plasma levels of intravenous drugs (1991)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 19 (1991), S. 635-645 
    Details
    ISSN: 1573-8744
    Schlagwort(e): pharmacokinetics ; linear systems analysis ; statistical moments
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract To rapidly achieve and maintain constant plasma concentrations most intravenous drugs must be administered as an initial bolus followed by a combination of exponentially declining plus constantrate infusions. In the clinical practice of anesthesia and critical care medicine this is often not practical without specialized equipment. In this paper a simpler approach of maintaining approximately constant plasma concentrations is developed using a loading dose with a two- stage infusion scheme (an initial rapid infusion reduced at a given time to a lower rate). Equations are developed for determining the rate of the infusions as well as the duration of the initial infusion by equating moments of the Laplace transform of the approximate infusion to the moments of the Laplace transform of an exact solution. This approach is independent of models and uses as parameters the moments of the curve relating the concentration following a single iv dose of unit magnitude as a function of time. The accuracy of this technique was assessed by computer simulation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01080871
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  • 70
    Digitale Medien
    Digitale Medien
    Estimation of amobarbital plasma-effect site equilibration kinetics. Relevance of polyexponential conductance functions (1991)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 19 (1991), S. 617-634 
    Details
    ISSN: 1573-8744
    Schlagwort(e): pharmacokinetics ; pharmacodynamics ; system approaches ; electroencephalogram ; amobarbital ; effect site equilibration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The time delay between drug plasma concentrations and effect has been modeled most commonly by the effect compartment approach, assuming first-order monoexponential equilibrium kinetics between plasma and effect site. So far this assumption has not been rigorously probed. The purpose of the present investigation was to model the delay between amobarbital plasma concentrations and EEG effect using a new approach based on system analysis principles. This approach models the equilibrium between plasma and effect site without assuming a specific kinetic structure. Assuming linear distribution kinetics between plasma and effect site, the relationship between the two variables may be described by a convolution type of linear operation, involving a conductance function ϕ(t),which is approximated by a sum of exponentials. Six male Wistarderived rats received an iv infusion of amobarbital at a rate of 10mg/kg per min until isoelectric periods of 5sec or longer appeared on the EEG. Frequent arterial blood samples were obtained and EEG was continuously quantified using aperiodic analysis. The amplitudes in the 2.5–30Hz frequency band were used as EEG effect measure. The delay between plasma concentrations and EEG effect was best modeled by a biexponential conductance function. The use of a biexponential conductance function resulted in a significant further reduction (41 ± 10%)in hysteresis when compared to a monoexponential function, indicating that the assumption of simple first-order monoexponential equilibration kinetics is inadequate. The use of a biexponential conductance function also resulted in a significantly different shape of the effect site concenration- EEG effect relationship and hence the estimated pharmacodynamic parameters, when compared with a monoexponential function. This relationship showed a biphasic behavior, with EEG effects being maximal at amobarbital concentrations of 29.6± 1.3mg/L. At 80.2±2.0mg/L the EEG effect was reduced 50%below baseline values. A comparison was made with the equilibration between amobarbital plasma and cerebrospinal fluid (CSF) concentrations. Six male Wistarderived rats received an iv infusion of amobarbital, 10mg per min for 15min. Arterial blood and CSF samples were taken simultaneously at regular intervals. The equilibration between plasma and CSF concentrations was best fitted by a monoexponential conductance function. Significant differences in equilibration profiles of CSF and effect site with the plasma site were observed. To reach 50%equilibrium the effect site requires 2.5±0.3min and the CSF 3.5±0.2min, to reach 95%the values were, respectively, 90± 27and 15± 1min. This suggests that CSF is kinetically distinguishable from the effect site.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01080870
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  • 71
    Digitale Medien
    Digitale Medien
    A pharmacokinetic model describing the removal of circulating radiolabeled antibody by extracorporeal immunoadsorption (1991)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 19 (1991), S. 385-403 
    Details
    ISSN: 1573-8744
    Schlagwort(e): immunoadsorption ; pharmacokinetics ; extracorporeal ; monoclonal antibody ; compartmental model ; simulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Extracorporeal immunoadsorption is a new technique for removal of circulating radiolabeled antibody from the peripheral blood (1) to reduce background activity for improved tumor imaging, and (2) to reduce whole-body and marrow toxicity when high doses of radiolabeled antibodies are used for antitumor therapy. A pharmacokinetic model was developed to describe plasma disappearance of111In -KC-4G3 prior to, during, and after immunoadsorption in humans. The model is developed based on a two-compartment open model, and during immunoadsorption a third compartment is added for removed radioactivity by the immunoadsorption column. Goodness-of-fit statistics indicate a good fit of the model to the data. The resulting pharmacokinetic parameters for a selected patient are V1=2.64L, Vss=3.64 L, t1/2α=3.77hr, and t1/2β hr. The immunoadsorption clearance (CL1A=19.3 ml/min) was 21-fold greater than the patient's plasma clearance (CL10=0.899 ml/min), indicating a very effective immunoadsorption process. The model predicts an increase in plasma radioactivity upon termination of immunoadsorption, probably due to redistribution of radioactivity from the extravascular compartment to the plasma in response to the rapid decline in plasma radioactivity during immunoadsorption. Two series of simulations were performed to examine the influence of onset time and duration of immunoadsorption. In series one the onset time was varied and in series two immunoadsorption duration was varied. In series one, the predicted radioactivity amounts adsorbed by the immunoadsorption column ranged from 75% of the injected dose (4-hr onset) to 52% of the injected dose (24-hr onset). In series two, immunoadsorbed radioactivity ranged from 32% (2-hr duration) to 64% of the injected dose (12-hr duration). When instituted as early as 4 hr, the predictions suggest that earlier immmoadsorption onset improves the effectiveness of radioactivity removal, relating to higher early circulation concentrations, and longer immunoadsorption periods remove more radioactivity, but also result in larger predicted radioactivity redistribution from tissue to plasma. To employ the immunoadsorption procedure for tumor imaging and therapy optimally, the data and our predictions indicate that a compromise must be made that will balance immunoadsorption onset and duration against tumor radioactivity uptake and subsequent radioactivity redistribution from tissues back to plasma. Together with biologic considerations providing sufficient antigenantibody interaction and dependent on the utilized radioisotope, these data support the utility of extracorporeal immunoadsorption during the radioimmunodetection of cancer and for future therapeutic applications.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01061663
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  • 72
    Digitale Medien
    Digitale Medien
    A kinetic-dynamic model to explain the relationship between high potency and slow onset time for neuromuscular blocking drugs (1991)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 19 (1991), S. 537-552 
    Details
    ISSN: 1573-8744
    Schlagwort(e): Modeling ; neuromuscular blocking drugs ; pharmacodynamics ; pharmacokinetics ; potency ; onset time
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract To account for experimental data showing increased onset time with increased potency of neuromuscular blocking drugs, a pharmacokinetic-pharmacodynamic model is presented. It is characterized by a finite concentration of receptors (R)in the effect compartment. Transfer from central to effect compartment is linearly related to concentration gradient. A sigmoid Emax model is used to describe the relationship between receptor occupancy and effect. Plasma concentrations found in the literature are used. Differential equations are solved numerically for equipotent doses of drugs of different potencies. Because the density of receptors constitutes a significant drain of drug molecules for potent drugs, the model predicts an inverse relationship between speed of onset and potency. The concentration of receptors in the effect compartment Rwhich best fits experimental data obtained in humans is 0.28 Μmol/L. With this value of R,onset times are prolonged when the ED95 (dose for 95% blockade) is less than 0.1 Μmol/kg. It is concluded that, in the development of a short-acting nondepolarizing neuromuscular blocking drug, agents having an ED95 of 0.1 Μmol/kg or greater appear more promising.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01062962
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  • 73
    Digitale Medien
    Digitale Medien
    System analysis in multiple dose kinetics: Evidence for saturable tubular reabsorption of the organic cationN 1-methylnicotinamide in humans (1991)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 19 (1991), S. 553-574 
    Details
    ISSN: 1573-8744
    Schlagwort(e): pharmacokinetics ; N 1-methylnicotmamide ; nicotinic acid metabolite ; organic cation ; saturation of tubular reabsorption ; tubular secretion ; system analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The renal clearance of N1-methylnicotinamide (NMN) was studied in 8 young women at physiological steady state and at steady state following a combined loading bolus and in infusion. Urinary NMN concentrations were determined using a new HPLC method, plasma levels by a conventional fluorescence method. At physiological levels net tubular secretion of NMN was evident due to a renal fractional excretion, i.e., a ratio of renal NMN clearance to creatinine clearance, above unity. Increasing plasma concentrations lead to an increase in the fractional excretion, indicating saturation of the underlying tubular reabsorption process. Binding to plasma proteins was excluded by ultra-filtration experiments. Clearances measured at physiological levels were about one half of the maximum renal clearance attained following the infusion. This maximum value was approximately six times the creatinine clearance and may be a useful approximation of the renal plasma flow. System analysis, including a novel method to calculate the net response following a multiple input, was used to determine the pharmacokinetic system parameters.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01062963
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  • 74
    Digitale Medien
    Digitale Medien
    Required beta blocker profile in the elderly (1991)
    Springer
    Cardiovascular drugs and therapy 4 (1991), S. 1273-1280 
    Details
    ISSN: 1573-7241
    Schlagwort(e): beta blockade ; elderly ; pharmacokinetics ; renal function ; renin ; hemodynamics ; respiratory function ; diabetes mellitus ; lipid profile ; celiprolol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In the truly elderly, a complex balance between compensatory processes and impaired organ function allows reasonably normal physical function. It is argued that beta blockade should have certain desirable qualities to minimize any impairment of organ function, thereby upsetting the quality of life. Thus a simple pharmacokinetic pattern without hepatic metabolism is less likely to cause unexpected variation in blood levels of the beta blocking agents and to have fewer risks of interactions with other drugs including nicotine. Renal-excreted beta blockers-such as atenolol, nadolol, and celiprolol-do, however, need downward dose adjustment when the glomerular filtration rates fall. The elderly are frequently categorized as having a low renin profile, which in the view of some workers may make a vasodilatory beta blocker more desirable. Hemodynamic advantages of such agents include the prime site of attack in hypertension on the increased peripheral vascular resistance, increasingly fundamental with a prolonged duration of hypertension and therefore with the aging process. Furthermore, a normal heart rate with a sustained cardiac output may avoid symptomatic bradycardia. In the elderly, respiratory function may be impaired so that loss of elastic recoil causes elderly emphysema. A highly cardioselective beta blocker should be an advantage. Finally, minimal interference with glucose and lipid metabolism should also be desirable goals.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00114233
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  • 75
    Digitale Medien
    Digitale Medien
    CINA: a software to Compose INfusion sheets for IV Anesthetic drugs (1991)
    Springer
    Journal of clinical monitoring and computing 8 (1991), S. 225-229 
    Details
    ISSN: 1573-2614
    Schlagwort(e): anesthetics ; intravenous ; pharmacokinetics ; computers ; simulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Medizin
    Notizen: Summary CINA is a software which uses LOTUS 1-2-3 commands and macros and it runs on an IBM PC. It contains an extensive database of three sections. Section 1 includes a list of several models of commercialized infusion devices. Section 2 presents the available IV packagings for a list of IV drugs. Section 3 contains the record of IV standard infusion regimens for each drug. Any other new infusion device, drug, or standard infusion regimen can be added or modified. The software verifies the compatibility of the prescribed infusion device according to the available drug packaging contained in the database. Moreover, it converts the infusion steps into the flow-rate units of the selected infusion device according to the patient's weight and the chosen drug concentration. Finally, the software allows the storage of all the information on a disk file or outputting on a printer.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01738896
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  • 76
    Digitale Medien
    Digitale Medien
    Antiparkinsonian dopamine agonists: a review of the pharmacokinetics and neuropharmacology in animals and humans (1991)
    Springer
    Journal of neural transmission 3 (1991), S. 151-201 
    Details
    ISSN: 1435-1463
    Schlagwort(e): Dopamine agonists ; Parkinson's disease ; apomorphine ; bromocriptine ; lisuride ; pergolide ; SKF 38 393 ; quinpirole ; pharmacokinetics ; biotransformation ; neuropharmacology ; neurobiochemistry ; rodents ; dog ; monkey ; human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary With the intention of compensating for the deficit of endogenous dopamine (DA) in the basal ganglia of Parkinsonian patients by substitution with agents which directly stimulate central DA receptors, synthetic DA agonists have been introduced almost 20 years ago for the symptomatic treatment of Parkinson's disease. The original expectation that DA agonists would be able to completely restore extrapyramidal motor function in Parkinsonian patients has turned out as too mechanistic and simplicative. However, undoubtedly DA agonists have improved therapeutic possibilities in Parkinson's disease. Thus, clinical evidence from controlled chronic studies in patients indicates that the therapeutic results following the early application of DA agonists in combination with L-DOPA on a long-term base are superior to the respective monotherapy. However, none of the DA agonists currently employed for antiparkinsonian treatment i.e. apomorphine and the ergoline derivatives bromocriptine, lisuride and pergolide, is optimal with respect to pharmacokinetic properties (poor oral bioavailability with considerable intra-and interindividual variation) or pharmacological profiles (low selectivity for DA receptors in case of the ergot agonists). The pathophysiology underlying Parkinson's disease which turned out more complex than initially expected might provide another explanation for the limited therapeutic potential of DA agonists. Therefore, apart from summarizing the pharmacokinetics, biotransformation, neuropharmacology and neurobiochemistry, of the DA agonists employed clinically, the present article also reviews physiological aspects of (a) central dopaminergic neurotransmission including the topographical distribution of DA receptor subtypes and their functional significance, (b) the intracellular signal processing in striatal output neurons and (c) the intraneuronal mechanisms which integrate the various neurotransmitter signals converging on the striatal output neuron to a demand-adjusted effector cell response via the cross-talk between the different second messenger systems. Based on these considerations, potential pharmacological approaches for the development of improved antiparkinsonian drugs are outlined. There is a therapeutic demand for more selective and better bioavailable DA agonists. In particular, selective D-1 receptor agonists are highly desirable to provide a more specific probe than SKF 38 393 for clarifying the current controversy on the disparate findings in nonprimate species and monkeys or Parkinsonian patients, respectively, regarding the functional significance of D-1 receptors for the antiparkinsonian action of DA agonists or L-DOPA. The therapeutic importance of D-2 receptor activation is generally accepted; whether DA agonists combining a balanced affinity to both D-1 and D-2 receptors within one molecule (to some extent a property of apomorphine) might be superior to subtype-specific DA agonists remains to be tested clinically. Beside selective DA agonists with markedly increased absolute oral bioavailability, the following alternative approaches for the symptomatic treatment of Parkinson's disease seem worth pursuing: (a) diminuition of excitatory amino acid (EAA)-mediated neurotransmission in the basal ganglia output nuclei, e.g. by EAA receptor antagonists, (b) pharmacological manipulation of the intracellular second messenger signals generated by DA, EAA's or acetylcholine in the striatal output neurons. Furthermore, preliminary experimental evidence indicates that, apart from symptomatic treatment, a preventive (neuroprotective) therapy of Parkinson's disease might be conceivable with EAA receptor antagonists.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02259537
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  • 77
    Digitale Medien
    Digitale Medien
    Plasma concentrations of 5-methoxytryptamine, 5-methoxytryptophol and melatonin after 5-methoxytryptamine administration of golden hamsters: physiological implications (1991)
    Springer
    Journal of neural transmission 84 (1991), S. 33-43 
    Details
    ISSN: 1435-1463
    Schlagwort(e): 5-Methoxytryptamine ; 5-methoxytryptophol ; melatonin ; pineal ; HPLC ; pharmacokinetics ; golden hamster
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 5-Methoxytryptamine (5-MT), 5-methoxytryptophol (5-ML) and melatonin (Mel) were measured in the plasma after 2, 5, and 8 weeks administration of 25 Μg 5-MT to golden hamsters kept under long photoperiod. 5-MT showed a one compartment kinetic profile in the plasma with half lives of 14.8 min after 2 weeks, 15 min after 5 weeks and 19.1 min after 8 weeks. A rapid metabolism of 5-MT was shown, Mel and 5-ML being detected in the plasma following 5-MT administration. However it was also shown that the gonadal atrophy observed after 5-MT administration cannot be due to its metabolism into these 2 compounds. Indeed when exogenously administered at a dose generating the same plasma concentration as that observed after 5-MT, the gonadal regression observed after the association of 5-ML and Mel is much less than that observed after 5-MT. 5-MT is thus a compound of great physiological interest.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01249107
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  • 78
    Digitale Medien
    Digitale Medien
    Crystallization kinetics of poly(ethylene terephthalate). Part I: Kinetic equation with variable growth rate (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 110-115 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A new crystallization kinetic equation has been derived considering the decrease in growth rate. The average linear growth rate of spherulite was assumed to be proportional to the m-th order of the uncrystallized fraction of the crystallizing material. A modified Avrami equation, 1 - Vc = exp[-Kf(t)n], was used where f(t) is the integral of the growth function, (1 - Vc)m. The validity of the equation was tested by analyzing the isothermal crystallization kinetic data of poly(ethylene terephthalate) from the melt using differential scanning calorimetry.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310209
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  • 79
    Digitale Medien
    Digitale Medien
    The coupled relaxation model for toner melt rheology (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 99-103 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Process changes aimed at improving printer engine performance must take into consideration not only the process variables (such as nip temperature and pressure and process time to), but also the melt rheological variables (such as the characteristic time scale of the toner Tc). The melt rheology relevant to the electrophotographic toner fusing process is discussed. One criterion for toner quality can be conveniently measured through the Deborah number De, which is the ratio of Tc to to. Modification of the melt rheology by matrix polymer composition and carbon black size and concentration has previously been explored. Here, the melt rheology of toners with a range of gel content was studied using a step shear test. The coupled relaxation model was employed to fit the stress relaxation data. The viscoelastic properties were calculated from the melt data with this model. These properties were then used to estimate the strain deformation of the toner as it passes through the nip with arbitrary residence time and nip pressure as a function of gel content. This method can be used to match the toner melt properties with the processing conditions.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310207
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  • 80
    Digitale Medien
    Digitale Medien
    Masthead (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991) 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310301
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  • 81
    Digitale Medien
    Digitale Medien
    A unified simulation of the filling and postfilling stages in injection molding. Part II: Experimental verification (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 125-139 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The unified numerical simulation of the filling/postfilling stages of the injection-molding process described in Part I is compared in the present paper with experimental results obtained with instrumented test molds. Flush-mounted pressure traces in the delivery system as well as in the cavity are favorably compared with corresponding predictions for both an amorphous and a semicrystalline polymer. It is demonstrated that the present unified formulation is well suited to handle complicated molds where compressibility effects can become important even during the filling stage, as portions of the cavity fill and undergo a packing behavior even when other regions of the cavity are still only partially filled.
    Zusätzliches Material: 19 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310211
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  • 82
    Digitale Medien
    Digitale Medien
    A unified simulation of the filling and postfilling stages in injection molding. Part I: Formulation (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 116-124 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: This study employs a unified theoretical model to simulate the filling and postfilling stages of the injection-molding process. Implementation of such a model is based on a hybrid finite-element/finite-difference numerical solution of the generalized Hele-Shaw flow of a compressible viscous fluid under nonisothermal conditions. The shear viscosity of the polymeric material is represented by a Cross model for the shear-rate dependence and a WLF-type functional form for the temperature and pressure dependence, whereas the specific volume is modeled in terms of a double-domain Tait equation. The analysis also handles variable specific heat and thermal conductivity of the polymer as a function of temperature. Complex thin parts of variable thickness can be modeled and discretized by flat, triangular finite elements which may have arbitrary orientation in three-dimensional space, whereas runners and possible round pins or bosses in the part are represented as one-dimensional circular-tube elements. A control-volume scheme is employed that leads to automatic melt-front advancement during the cavity-filling stage.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310210
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  • 83
    Digitale Medien
    Digitale Medien
    Models for the compressibility of layered polymeric sponges (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 140-144 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The characteristic sigmoid compressive stress-strain relationships of sponges and their layered arrays are described by two kinds of mathematical models having three experimentally determined parameters. Since sponge compression is not accompanied by a significant cross-sectional area expansion, it was assumed that the stress in a multilayered array is the same in each layer. This enables prediction of the array's stress-strain relationship from the parameters of the individual layers and their known thickness. The applicability of the method is demonstrated with experimental data of two kinds of double-layered arrays of polyurethane sponges. It is shown that the arrays' compressive behavior can be satisfactorily predicted irrespective of the mathematical form of the model and whether the strain is expressed as engineering strain or Hencky's.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310212
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  • 84
    Digitale Medien
    Digitale Medien
    Development of density distributions in injection molded amorphous engineering plastics. Part I (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 145-152 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The gapwise density distributions of the injection molded specimens of two engineering thermoplastics, i.e., poly(phenylene ether) and poly(ether imide), were characterized employing the density gradient column technique. The samples were molded using a 40t Van Dorn injection molding machine. The effects of the thermal history on the density distribution of unconstrained quenched specimens were also investigated. In addition, various material properties, such as pressure-volume-temperature, isothermal contraction, and pressure induced densification behavior were characterized, for the two resins employed in this study. The moldings of the two resins exhibited different trends in their density distributions. These findings were explained in terms of the competing effects of cooling rate and the pressure history experienced by the engineering plastic resins during the molding cycle. The data collected were also used as input to mathematical modeling of density distributions in injection molded articles, which is reported in Part II of this article.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310302
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  • 85
    Digitale Medien
    Digitale Medien
    Steady solidification of non-Newtonian fluid flowing in a round tube (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 191-196 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The problem of steady solidification of a power law fluid flowing in a round tube was solved numerically. The fluid considered was a polymer with temperature dependent viscosity. The mathematical solution was obtained by using an implicit finite difference method. Results are presented to show the effects of the Peclet number, Nahme number, and the power law index on the profiles of the frozen layer. Melt temperature profiles at different axial locations are also presented.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310306
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  • 86
    Digitale Medien
    Digitale Medien
    Masthead (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991) 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310401
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  • 87
    Digitale Medien
    Digitale Medien
    A study on bicomponent two-layer slot cast coextrusion (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 197-203 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Extensional flow of a bicomponent two-layer slot cast coextrusion process has been studied. A Newtonian and an upper-convected Maxwell fluid were considered to be the two layers, respectively, and the two-layer flow was assumed to be steady and isothermal. This choice was made as a simple model for a system which consists of two distinctly different fluids in terms of their extensional behaviors. Present study considered only the draw-down region where the film thickness changes slowly with the distance from the die exit. For this region, asymptotic solutions could be obtained for two limiting cases in which the elasticity effect of the Maxwell fluid layer is small and the applied tension at the take-off is large, respectively. When the elasticity effect is small, the melt thickness and the velocity profiles are exponential as in the case of a Newtonian single-layer flow. When the applied tension is large, on the other hand, the velocity profile is shown to be near linear. Furthermore, the viscoelasticity effect of the Maxwell fluid layer becomes so dominant that it dictates the mechanics of the coextrusion flow even when its flow rate and shear viscosity may be much smaller than those of the Newtonian layer.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310307
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  • 88
    Digitale Medien
    Digitale Medien
    Masthead (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991) 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310501
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  • 89
    Digitale Medien
    Digitale Medien
    An experimental study of multiobjective dynamic optimization of a semibatch copolymerization process (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 353-364 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Optimal open loop control strategies are developed for a semibatch free radical copolymerization of methyl methacrylate and vinyl acetate using the multiobjective dynamic optimization method. A detailed kinetic model is validated through experimentation and used for the design of optimal controls. Both monomer feed rate and reactor temperature are varied to produce the copolymer of desired composition and molecular weight. The open loop control policies are implemented in a process control computer and tested on an experimental stirred tank polymerization system. Excellent agreement between the model predictions and the experimental data have been obtained.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310507
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  • 90
    Digitale Medien
    Digitale Medien
    Dynamics of a cascade of two continuous stirred tank polymerization reactors with a binary initiator mixture (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 333-352 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The dynamic behavior of two continuous stirred tank reactors in series has been investigated for free radical solution polymerization of styrene with a binary mixture of two initiators having different thermal decomposition activities. For a wide range of initiator feed composition, both reactors exhibit quite complex nonlinear steady state and transient behavior. When the reactor residence time is used as a bifurcation parameter, the second reactor can have up to five steady states. For certain range of reactor operating conditions, bifurcations to various types of periodic solutions have been observed, such as Hopf bifurcation, isolas, period doubling, period-doubling cascade, and homoclinics. The effects of other reactor variables, such as total initiator concentration, coolant temperature, and reactor volume ratio on the reactor dynamics, are illustrated to show the complex dynamic behavior of the two-reactor system catalyzed by a mixture of t-butyl perbenzoate and benzoyl peroxide.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310506
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  • 91
    Digitale Medien
    Digitale Medien
    Development of an in-line rheometer suitable for reactive extrusion processes (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 365-375 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: This paper presents the development of a novel in-line extrusion rheometer based on the flow of polymer through a wedge (vertically tapered slit). This rheometer is suitable for measuring changes in rheological properties on-line during reactive extrusion, because it can be used to estimate the viscosity for a range of shear rates without the need to change the polymer flow rate (i.e., extruder throughput). Equations have been developed to estimate the parameters of the power-law equation, used to describe the viscosity-shear rate relationship, from measurements of pressure drops along the wedge. An experimental in-line wedge rheometer has been built and used to measure the viscosity for a series of polypropylenes prepared via reactive extrusion. Viscosity measurements from the experimental in-line wedge rheometer are compared with measurements from a capillary rheometer. Good agreement is found between the capillary and wedge rheometer measurements.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310508
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  • 92
    Digitale Medien
    Digitale Medien
    Correction (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 391-391 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310511
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  • 93
    Digitale Medien
    Digitale Medien
    Masthead (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991) 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310101
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  • 94
    Digitale Medien
    Digitale Medien
    The design and manufacture of a graphite fiber reinforced poly(ether ether ketone) (PEEK) tetrahedron truss array (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1-5 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Orbital space structures are required to be lightweight, have high specific stiffness, have near-zero coefficient of thermal expansion, exhibit low outgassing, and be cost-effective. Graphite-reinforced thermoplastics have the potential to satisfy the criteria noted. However, prior to committing the materials to specific projects, technology demonstration and risk reduction is necessary. In order to demonstrate the application of fiber-reinforced thermoplastic composites for truss structure applications, a graphite-reinforced poly(ether ether ketone) (PEEK) composite tetrahedron truss array was designed and manufactured. The resulting structure clearly demonstrated that fiber-reinforced thermoplastic composites are a viable alternative to epoxy composites for orbital structures.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310102
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  • 95
    Digitale Medien
    Digitale Medien
    371°C (700°F) properties of celion 6000/N-phenylnadimide modified pmr polyimide compositesPart of this work was performed under the auspice of the Polymer Composite Branch of the Materials Division, NASA-Lewis Research Center, Cleveland, Ohio. (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 14-19 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The 371°C (700°F) properties of Celion 6000/N-phenylnadimide modified PMR-15 polyimide composites were investigated to determine the feasibility of using these materials at a 371°C (700°F) service temperature. The processing characteristics and physical and mechanical properties of the composite systems are presented. The results of the 371°C thermooxidative stability study suggest that the composite materials can be considered for short-term (at least 100 hours) application at 371°C.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310104
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  • 96
    Digitale Medien
    Digitale Medien
    Mechanical properties and mechanism of the degradation process of 316°C isothermally aged graphite fiber/PMR-15 composites (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 6-13 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A series of graphite fiber/PMR-15 polyimide composites, isothermally aged at 316°C in flowing air (100 cc/min) for time periods up to 2000 h, were investigated for mechanical property changes, fiber/resin interface changes, overall dimensional changes, and weight loss. The mechanism of the degradation process is suggested based on shear and flexural property measurements at room temperature and 316°C, optical micrographs of composite cross sections, and SEM analysis of fractured surfaces. The fiber materials investigated in composite form were Celion 6000 unsized and epoxy sized. G40-700 unsized and epoxy sized, and T40R and IM6 both unsized.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310103
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  • 97
    Digitale Medien
    Digitale Medien
    Interpenetrating polymer network approach to tough and microcracking resistant high temperature polymers. Part III. LaRC-RP71 (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 28-33 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A high performance semi-interpenetrating polymer network (semi-IPN) has been synthesized from Thermid-600 and LARC-TPI. Notable improvements in resin fracture toughness and graphite fiber reinforced composite microcracking resistance over the unmodified Thermid-600 neat resin and composite have been realized. The chemistry, processing, physical and mechanical properties, and phase morphology of the neat resin and composite reinforced with graphite fibers are presented.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310106
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  • 98
    Digitale Medien
    Digitale Medien
    Interpenetrating polymer network approach to tough and microcracking resistant high temperature polymers. Part II. LaRC-RP41 (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 20-27 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Recently, we reported on the interpenetrating polyimide network (IPN) approach to develop tough and microcracking resistant high temperature matrix resins for use in aircraft/aerospace structural components. One such polymer developed is designated LaRC-RP40. This new simultaneous semi-IPN was prepared from easy-to-process but brittle crosslinking PMR-15 and tough but difficult-to-process linear NR-150B2. Significantly improved toughness, microcracking resistance, and glass transition temperature over PMR-15 were realized from the combination. These property improvements were achieved without compromising ease of processing, high temperature mechanical performance, and cost effectiveness compared to PMR-15. These results encouraged us to further explore this approach for the development of a wider range of polymers of basic technological and economic interest. In the present work, we combine crosslinking PMR-15 and linear LaRC-TPI to provide a new sequential semi-2-IPN called LaRC-RP41. The physical and mechanical properties of the neat resin and composite reinforced with graphite fibers are presented. The phase morphology and phase stability of the neat resin and composite studied by various techniques are also discussed.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310105
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  • 99
    Digitale Medien
    Digitale Medien
    Mechanical properties in multidimensional composites (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 40-46 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The mechanical properties of three dimensional stitched composites were compared against those of the traditional two dimensional laminates. An attempt was made to correlate the change in properties to the change in the third directional fiber density. Tests conducted were the impact, three-point bending, damage tolerance, end notched flexure, and bending fatigue test. The results of these tests show that the third directional fibers can effectively inhibit delamination by increasing the interlaminar shear strength. Three dimensional composites also possess better damage tolerance, fracture toughness, and fatigue life. However, a high stitching density can degrade the in-plane properties of the composites.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310108
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  • 100
    Digitale Medien
    Digitale Medien
    Environmental effects on the water absorption and mechanical properties of carbon fiber reinforced PPS and PEEK composites. Part II (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 34-39 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Research has been conducted to investigate the water absorption in carbon fiber reinforced poly(ether ether ketone) (PEEK/CF) and poly(phenylene sulfide) composites (PPS/CF). Effect of humidity and temperature on tensile, flexural, and impact strength of these composites were also studied. Results indicated that the water absorbed in PPS/CF and PEEK/CF are 0.059 %wt, 0.130 %wt, 0.138 %wt, and 0.153 %wt at 80°C. 75 %RH and 85 %RH, respectively. The diffusion process is a classical Fickian diffusion in the temperature range investigated. The activation energies of diffusion are 667 cal/g-mole (for PPS/CF) and 8934 cal/g-mole (for PEEK/CF) at 80°C and 75 %RH. The retention of mechanical properties of these composites is very good under hot-wet conditions. These composite materials can be served as high performance materials even in the hostile environment. PEEK/CF composites shows excellent mechanical properties retention even at 80°C, 75 %RH, and 85 %RH.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310107
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