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  • 1
    Electronic Resource
    Electronic Resource
    USA/Oxford, UK : Blackwell Science Ltd
    Cephalalgia 3 (1983), S. 0 
    ISSN: 1468-2982
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 26 (1984), S. 381-388 
    ISSN: 1432-1041
    Keywords: midazolam ; hypnotic drug ; benzodiazepine ; pharmacokinetics ; aged patients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of midazolam, an imidazo-benzodiazepine derivative, have been studied in 13 subjects over the age of 60 years who received the drug intravenously (0.07 mg kg−1) as an induction agent for endoscopy. Two to three days later, 6 of these subjects received 5 mg of midazolam intramuscularly, and another 6 of the subjects received 10 mg of the drug orally. The plasma concentration-time curves were again studied pharmacokinetically. After intravenous dosing, the mean (± SD) elimination half-life (2.14±1.24 h) showed a statistically significant trend to increase with age in the subjects older than 60 years. While the mean (± SD) clearance value (0.30±0.19 l kg−1h−1) tended to fall with age in the elderly subjects, this trend was not statistically significant. Apparent volume of distribution did not appear to be related to advancing age beyond 60 years, and this parameter (mean ± SD) did not differ to a statistically significant extent between the aged subjects (0.77±0.47 l kg−1) and the young subjects studied previously (1.09±0.58 l kg−1). Atropine premedication did not appear to alter the dispositional parameters of the intravenously administered drug. Intramuscularly administered midazolam was absorbed rapidly. Bioavailability appeared incomplete (F=0.59±0.15, mean ± SD), possibly due to saturable elimination of the drug at the higher plasma levels which were obtained after intravenous midazolam. Oral bioavailability, relative to intravenous, was 0.34±0.17, (mean ± SD), with an appreciable but variable lag time (0.74±0.40 h, mean ± SD). Orally, in the dose used, the drug was an inefficient hypnotic with four of the six subjects failing to attain the plasma drug level of 44–50 µg l−1, which appeared to be the approximate threshold for sleep. It is impossible to know whether this failure represents an age related effect on drug absorption, or is a consequence of the upper alimentary tract abnormalities for which the endoscopies were done.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 27 (1984), S. 105-110 
    ISSN: 1432-1041
    Keywords: phenytoin ; epileptic women ; pharmacokinetics ; bioavailability ; pregnancy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Five epileptic women needing to commence phenytoin therapy during pregnancy received a single intravenous and a single oral dose of phenytoin several days apart before starting regular intake of the drug. Plasma phenytoin concentration — time data were analysed by three different pharmacokinetic techniques. However assessed, the mean oral bioavailability of the drug proved to be about 90% of the intravenous bioavailability. This finding makes it unlikely that impaired bioavailability accounts for the increase in oral phenytoin dosage necessary in pregnancy to maintain plasma phenytoin concentrations at pre-pregnancy values. Phenytoin clearance in the pregnant subjects was approximately double the published values for phenytoin clearance in nonpregnant persons. This suggests that increased (metabolic) clearance accounts for the increased phenytoin dosage requirement of pregnancy.
    Type of Medium: Electronic Resource
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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 25 (1983), S. 65-67 
    ISSN: 1432-1041
    Keywords: tizanidine ; pharmacokinetics ; spasticity ; multiple sclerosis ; haematological parameters ; electromyogram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The time-course of plasma concentrations of the antispasticity agent tizanidine were measured by a specific radioimmune-assay in six adults who had severe spasticity due to multiple sclerosis. The drug was given as a single oral 4 mg dose to each subject. The drug had a mean absorption half-life of 0.30±0.155 h following a mean lagtime of 0.361±0.118 h, and a mean terminal elimination half-life of 4.16±2.06 h. Only 2.65±0.82% of the dose was excreted unchanged in urine in 2 h. Calculated values of clearance and apparent volume of distribution were almost certainly overestimates as it seems probable that the orally-administered drug undergoes significant presystemic elimination (its bioavailability was not determined in the investigation here reported). Relief of spasticity, from the dosage used, was relatively slight and appeared greatest at the time of peak plasma levels of the drug.
    Type of Medium: Electronic Resource
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  • 9
    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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  • 10
    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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