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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 12 (1977), S. 451-456 
    ISSN: 1432-1041
    Keywords: Bioavailability ; carbamazepine ; elimination ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The time-courses of plasma carbamazepine concentrations were followed in six apparently healthy adult subjects who, at different times, took single oral drug doses of 200, 400, 500, 600, 700, 800 and 900 mg. There were some suggestions of impaired bioavailability of the drug when given in tablet form. The following values were obtained for various pharmacokinetic parameters:k abs =0.176±0.209 h−1;k=0.0203±0.0055 h−1; T1/2=37.5±13.1 h; VD=0.825±0.1041 · kg−1; Clearance=0.0163±0.0061 l · kg−1. The elimination rate constant showed a statistically significant increase with increasing drug dose. This may help explain the clinical observation that the rate of rise of steady state plasma carbamazepine concentrations tends to decrease with dose increase in patients taking carbamazepine alone.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 16 (1979), S. 141-147 
    ISSN: 1432-1041
    Keywords: prazepam ; N-desmethyldiazepam ; bioavailability ; pharmokinetics ; electron-capture gasliquid chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary An original electron-capture gas chromatographic assay was developed for simultaneous measurement of plasma levels of the benzodiazepine derivative prazepam and of its principal unconjugated metabolite, N-desmethyldiazepam. The assay was used to study the pharmacokinetics of the drug and its comparative bioavailability from tablets and from a specially prepared solution. Nine healthy adult volunteers were studied. Each volunteer on one occasion took 30 mg of the drug in tablet form, and on another occasion 30 mg of the drug in solution. In all subjects, N-desmethyldiazepam appeared in plasma shortly after prazepam appeared and reached a peak within four hours of prazepam ingestion. Thereafter plasma N-desmethyldiazepam levels were much higher than plasma prazepam levels throughout. Prazepam became undetectable within six hours of intake, whereas its metabolite could still be measured in plasma fourteen days after dosage. Thus much of the pharmacological action of prazepam may be mediated through its metabolite, N-desmethyldiazepam. In five of the nine subjects, areas under the plasma level curves for the metabolite were not markedly different for the tablet and solution formulations studied. In the other four subjects the area under the curve for the tablets was 50% to 80% of the area under the curve for the solution. The time to reach peak plasma level for the metabolite was shorter after the solution formulation (mean 2.0±SD 1.2 h) than after the tablet formulation (mean 4.2±SD 1.7 h).
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 20 (1981), S. 465-471 
    ISSN: 1432-1041
    Keywords: metoclopramide ; pharmacokinetics ; bioavailability ; first-pass effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The time courses of plasma metoclopramide concentrations were followed in six subjects after oral and intravenous single dose administration. Plasma concentration-time data following i.v. administration in each subject were found to fit a two compartment model with a mean terminal half-life of 4.55 h±0.80 h and a mean distribution half-time of 0.35 h±0.09 h. Volumes of distribution were high (3.43±1.181 · kg−1), and clearances (0.53±0.191 · kg−1h−1) approached liver plasma flow. This suggests that metoclopramide occurs at higher concentrations in tissues than in plasma, and that its clearance is probably limited by liver blood flow rather than liver metabolic capacity. The post-absorption decline in metoclopramide plasma levels after oral administration was also biexponential in each subject. The terminal half-life was 5.17 h±0.98 h. Mean volume of distribution and mean clearance were similar to intravenous values (after adjustment for bioavailability). Oral absorption was rapid with peak plasma concentrations being reached at a mean time of 0.93 h. A mean bioavailability of 0.77 was calculated for the six subjects, and it was postulated that this incomplete availability is due to a first-pass effect. The inter-individual variation in the degree of ‘first-pass’ was considerable (0.47–1.14).
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 24 (1983), S. 727-732 
    ISSN: 1432-1041
    Keywords: propranolol ; foetus ; placenta ; metabolism ; pregnancy ; plasma levels ; plasma protein binding ; delivery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Propranolol (P) and all of its major known metabolites were found in maternal plasma, cord plasma and neonatal plasma in 10 women at term, irrespective of the P doses administered and the time elapsed (up to 15 h) between administration of the last P dose and delivery. The ratios of cord plasma to simultaneous maternal plasma levels for propranolol and its major metabolites (mean±SD) were: propranolol 0.32±0.17, propranolol glucuronide 0.86±0.36, 4-hydroxypropranolol 1.4±1.0, 4-hydroxypropranolol glucuronide 0.71±0.45 and naphthoxylactic acid 3.0±1.6. P binding in cord plasma at delivery was 67.2±3.9% (mean±SD) which was significantly less (‘t’=13.4,df=13,p〈0.001) than the P binding in maternal plasma at delivery (87.5±1.6%, mean±SD). The plasma protein binding (mean±SD) of naphthoxylactic acid in cord plasma (98.6±0.2%) was significantly greater (‘t’=3.808,df=4,p〈0.02) than the naphthoxylactic acid binding in maternal plasma at delivery (97.6±0.4%). When the simultaneous concentrations of P and naphthoxylactic acid in maternal and cord plasma are compared in conjunction with protein binding and ionic effects, it would seem that metabolism of P does occur in the placental/foetal unit.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 24 (1983), S. 777-785 
    ISSN: 1432-1041
    Keywords: aspirin ; migraine ; salicylic acid ; metoclopramide ; drug absorption ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of aspirin (ASA) in acute migraine attacks, and the influence of metoclopramide on ASA disposition, were studied in 32 attacks in 30 patients. An intergroup comparison was made between normal volunteers, and the migraineurs, who were assigned at random to one of three treatment groups: a) oral ASA only (900 mg); b) 10 mg oral metoclopramide + oral ASA 900 mg; c) 10 mg i. m. metoclopramide + oral ASA 900 mg. Plasma ASA and SA levels were measured serially over 2 h, and the resultant data evaluated pharmacokinetically. Metoclopramide plasma levels were also determined over 2 h, and the results compared with a second group of normal volunteers. The rates of oral ASA absorption and elimination were unaffected by migraine. Mean absorption rate constants of 14.15±9.48 h−1 (normals), 7.91±3.42 h−1 (ASA only), 6.74±3.26 h−1 (ASA + oral metoclopramide) and 8.12±2.82 h−1 (ASA + i. m. metoclopramide) were calculated. Mean elimination rate constants ranged from 2.56 h−1 to 3.37 h−1, and did not differ significantly between controls and migrainous patients. Values for absorption lag time, however, were higher in migraine patients treated with ASA alone than in any other group. The amount of ASA absorbed unhydrolysed was also lower in this group. SA levels appeared unaffected either by the migraine attack, or by metoclopramide administration, over the period of study. Metoclopramide plasma levels were significantly lower during migraine attacks, and the amount of drug absorbed up to 2 h from dosing was also reduced, as compared with non-migrainous subjects. It was concluded that acute migraine caused a delay in orally administered ASA reaching its absorption sites, probably as a result of gastric stasis, and may have decreased the amount of ASA absorbed. The prior administration of metoclopramide, either orally or intramuscularly, reduced the absorption lag time, and thus promoted the early absorption of ASA, probably by restoring alimentary tract motility.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 25 (1983), S. 481-490 
    ISSN: 1432-1041
    Keywords: propranolol ; pharmacokinetics ; pregnancy ; hypertension ; naphthoxylactic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of propranolol (P) and its major metabolites, propranolol glucuronide (PGLUC), 4-hydroxypropranolol (4OHP), 4-hydroxypropranolol glucuronide (4OHPGLUC) and naphthoxylactic acid (NLA), (Walle et al. 1972) were determined, whenever possible, in the first, second and third trimesters of pregnancy in thirteen patients and also when these patients were at least three months post-partum. No correlations were found between the mean arterial blood pressure (post-therapy) or the fall in blood pressure as a result of the P therapy (p〉 〉0.05) and P dose, peak P plasma concentrations, peak 4-hydroxypropranolol (4OHP) plasma concentrations or peak (P plus 4OHP) plasma concentrations. However, a positive nonlinear relationship was found between the daily P dose (independent variable) and peak P plasma concentrations over the daily dose range 30–160 mg/day. The elimination half-lives of NLA for patients in the third trimester of pregnancy were significantly shorter (p=0.072, df=13) than those when the patients were at least three months post-partum. Also, the areas under the plasma level-time curves of NLA were significantly less (p〈0.05, df=13) for patients in the third trimester of pregnancy than when these patients were at least three months post-partum. The results of this study indicate that the pharmacokinetics of P, PGLUC, 4OHP and 4OHPGLUC are not significantly altered by pregnancy. However, the kinetics of NLA do appear to be altered. The formation of NLA by N-dealkylation of P and further oxidation, appears to be competitively inhibited by unidentified substances, perhaps endogenous steroids, especially in the third trimester when compared to at least three months post-partum.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 47 (1994), S. 355-360 
    ISSN: 1432-1041
    Keywords: Carbamazepine ; metabolism ; autoinduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Six healthy young adult male volunteers were given two 600 mg (2540 μ moles) oral doses of carbamazepine (CBZ) 5 days apart. Serial concentrations of CBZ and its 10,11-epoxy (CBZ-epoxide) and 10,11-dihydro-10,11-trans-dihydroxy (CBZ-diol) metabolites in plasma, and daily excretions of these substances and the 2-hydroxy (2-OH-CBZ), 3-hydroxy (3-OH-CBZ) and 9-hydroxymethyl-10-carbamoylacridan (acridan) metabolites in urine were followed for 5 days after each dose. Pharmacokinetic analysis showed that autoinduction of CBZ metabolism was present within 6–10 days of the initial drug dose. The mean oral clearance of CBZ increased from 1.48 to 1.74 l·h− (difference 0.26 l·h−, 95% confidence interval 0.11 to 0.41 l·h−) and the mean percentage urinary recovery of the amount of CBZ eliminated increased from 41.8% to 44.6% (difference 2.8%, 95% confidence interval 0.5 to 5%) between the two studies 5 days apart. The data for daily clearance to metabolite and the time-courses of the plasma CBZ-epoxide to CBZ and CBZ-diol to CBZ concentration ratios suggested that autoinduction had begun by the second day after CBZ intake, and involved not only the epoxide-diol pathway but, to a lesser extent, the oxidations to phenolic derivatives.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 24 (1983), S. 103-108 
    ISSN: 1432-1041
    Keywords: dexamethasone ; bioavailability ; pharmacokinetics ; ‘first-pass’ effect ; pre-systemic elimination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and oral biovailability of dexamethasone were studied in 6 patients with neurological disease being treated with high dosages of the drug. A specific high performance liquid chromatographic assay was used to measure dexamethasone concentrations. Unlike the previously published mean figure of 0.78 for the oral bioavailability of the drug given in single doses to healthy volunteers, the mean bioavailability of dexamethasone in the patients studied was 0.53±SD 0.40. It appeared more likely that this incomplete bioavailability was due to presystemic elimination than to poor absorption. The intravenous clearance of the drug was relatively high (0.4902±SD 2291 l kg−1, approximately 65% of expected hepatic plasma flow), the oral clearance higher (2.5804±SD 3.2181 l kg−1 h−1) while the absorption rate constant (4.8729±8.4998 h−1), suggested rapid absorption after oral administration. Prior phenytoin and possibly prior dexamethasone therapy is likely to have contributed to the higher clearance values of the drug in these patients than the values reported in healthy volunteers after single dose studies.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 19 (1981), S. 271-278 
    ISSN: 1432-1041
    Keywords: midazolam ; benzodiazepine ; pharmacokinetics ; gas-liquid chromatography ; first-pass metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Midazolam, a new water-soluble benzodiazepine, was administered as: i) 5 mg intravenously, ii) a 10-mg oral solution and iii) a 10-mg oral tablet, to six volunteers whose informed consent had been obtained. Midazolam plasma concentrations were measured using an electron-capture gas-liquid chromatographic assay. After 5-mg intravenous midazolam, subjects fell asleep within 1–2 min and continued to sleep for an average of 1.33 h. After oral midazolam intake (solution or tablets), drowsiness appeared after a average of 0.38 h (range 0.25–0.55 h) and sleep continued for an average of 1.17 h. The time to reach peak plasma midazolam concentration after the 10-mg solution dose (0.37±0.45 h) did not differe significantly (‘t’=2.04, df=10,p〉0.05) from the time to reach peak plasma midazolam level after the 10-mg tablet dose (0.74±0.45 h). The terminal half-life, (t1/2), of midazolam in plasma was 1.77±0.83 h and there was no significant difference between the mean terminal half-life values obtained for the three midazolam formulations. The mean total clearance (Cl), of midazolam after 5-mg intravenous administration was 0.383±0.094 l·kg−1·h−1. The first pass effect, F, determined experimentally (0.36±0.09) indicated the substantial first pass metabolism of midazolam. The percentage of the midazolam dose excreted unchanged in urine in four subjects during the 0-8-h urine collection interval was very small (0.011%–0.028%).
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1041
    Keywords: acetylsalicylic acid ; salicylic acid ; effervescent tablets ; enteric coated tablets ; liquid chromatography ; platelet aggregation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Single doses of effervescent tablets (1200 mg) and enteric coated (EC) tablets (1300 mg and 650 mg) of acetylsalicylic acid (aspirin, ASA) were given to healthy volunteers in random order. Plasma ASA and salicylic acid (SA) levels were measured and concurrent in vitro measurements of the volunteers' platelet aggregation were carried out. The effervescent preparation resulted in peak ASA concentrations of 17–40 mg/l, achieved 20 to 30 min after a 1200 mg dose, whereas peak ASA levels of 0.01–0.37 mg/l were observed 4–6 h after a 650 mg dose of the EC preparation. With all the aggregating agents that were added to the test system maximum inhibition of platelet aggregation (about 50% of pre dose levels) was seen 1.0 h after the effervescent ASA dose, and persisted to at least 24 h, but with the EC preparation not until 24 h, at which time the degree of inhibition was also about 50% of pre-dose levels. A 1.0 g dose of sodium salicylate had no effect on in vitro platelet function. It was concluded that mean plasma levels of ASA of less than 0.25 mg/l are sufficient to depress aggregation by approximately 50%. A low dose of ASA taken daily either as effervescent ASA or EC ASA, significantly inhibits platelet aggregation and so may reduce the risk of ischaemic episodes in susceptible patients.
    Type of Medium: Electronic Resource
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