Factors contributing to variability in drug pharmacokinetics. III. Metabolism.
Explore the source record for details and available documents.
Biomedical subjects
Publications and source records attributed to D B Jack.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Higher AUC and Cmax values were obtained for metoprolol, oxprenolol and propranolol in groups receiving the low-dose oestrogen-ethinyl oestradiol oral contraceptive, but statistical significance was reached only with metoprolol AUC. The oral contraceptive had the opposite effect on acebutolol AUC and Cmax but this was not significant. The oral contraceptive had no detectable effects on the tmax and t 1/2 values of any of the beta-adrenoceptor blockers.
Nifedipine, metoprolol and atenolol were administered orally to young, healthy volunteers. Each drug was given alone and nifedipine was also given with both beta-adrenoceptor blockers. Each drug was given for 3 days immediately before the study days. Plasma and urine drug concentrations were measured and the relevant pharmacokinetic parameters calculated. No pharmacokinetic interaction between nifedipine and the beta-adrenoceptor blockers was revealed.
Explore the source record for details and available documents.
The Rosin Rammler Sperling Weibull distribution and its use in the analysis of complex data is explained with reference to metoprolol and acebutolol AUC values and isoniazid plasma concentrations. The technique is then applied to sparteine and debrisoquine data to resolve populations into distinct sub-groups. Goodness of fit is measured by applying the chi 2 test to the untransformed data. The method is simple to use and sub-groups can be identified rapidly. Each sub-group can be characterised by a simple exponential equation.
Explore the source record for details and available documents.
The claim for polymorphism in the metabolism of metoprolol is based on a logical fallacy. A frequency distribution of metoprolol AUC data is presented and, although highly skewed, no evidence of more than a single population is apparent. Plasma and urine metoprolol and metabolite data are also presented to support this.
Explore the source record for details and available documents.
Pharmacokinetic data for diclofenac sodium has been well established in healthy volunteers, whereas in patients with rheumatoid arthritis very little information is available in the literature. A single oral dose of enteric-coated diclofenac sodium was given to 10 patients with active rheumatoid disease, adopting the same procedures used for a group of 10 healthy volunteers in whom pharmacokinetic data was already available. Plasma specimens were collected over a period of 8h following administration and concentrations of diclofenac determined by GLC. Resulting plasma concentration curves were similar to those obtained in the healthy subjects in that areas under curves and terminal half-lives were comparable. However, peak concentrations of diclofenac were significantly reduced in the rheumatoid patients. The lower peak concentrations were correlated with the lower serum albumin levels in the patients which are associated with active rheumatoid disease.
Plasma concentrations of metoprolol, propranolol oxprenolol, acebutolol and its metabolite diacetolol were measured after single oral doses in young health volunteers. In order to assessed the inter- and intra-subject variability the following pharmacokinetic parameters were compared: AUC0(24), Cmax, tmax and t 1/2. The smallest variation in inter-subject variability was seen with oxprenolol and acebutolol: intrasubject variability was more uniform. Female volunteers taking an oral contraceptive generally had higher AUC0(24) and Cmax values than those not. This finding reached statistical significance only for metoprolol AUC0(24).
1 A new osmotic pressure mediated delivery system for metoprolol (Lopresor Oros) has been evaluated by measuring the haemodynamic effects and pharmacokinetics after single and multiple oral dosing in young healthy volunteers. 2 Similar studies have been carried out in the same group using equivalent single and multiple oral doses of the commercial slow-release preparation (Slow Lopresor). 3 The new osmotic delivery system produces a more uniform haemodynamic response: a plateau metoprolol concentration in plasma is reached about 6 h after dosing and is maintained for 10 h.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
A single dose of enteric-coated diclofenac sodium was taken fasting and immediately after a standard breakfast by twelve healthy volunteers. A considerable delay in the onset of absorption was observed, non-fasting, varying from 2.5 to 12 h compared with 1.5 to 2.75 h when fasting. Peak plasma concentrations were reduced after food but areas under plasma concentration-time curves were comparable. Six subjects then took part in a study involving single and repeated dosing under fasting and non-fasting conditions. As before, prolonged and variable delays were observed when the enteric-coated tablets were taken after food. On repeated dosing, maximum plasma concentrations were reached after 6 h non-fasting compared with 2.5 h fasting. Peak plasma levels were, however, similar.