No abstract

1 The pharmacokinetics of physostigmine were investigated in a three-way crossover design in six healthy, male volunteers comparing a physostigmine transdermal system (PTS), an oral solution and an i.v. infusion. 2 A single application of the patch over 24 h produced detectable plasma drug concentrations after a mean lag-time of 4 h. Thereafter, the drug was absorbed continuously from the PTS and putative therapeutic plasma concentrations were measured over approximately 18 h. 3 A mean absolute bioavailability of 36% was determined for the transdermal system and 3% for the oral solution. In comparison with the oral solution, interindividual variability of pharmacokinetics was less with the PTS. 4 The mean amount of physostigmine released from the transdermal system after 24 h was 5.7 mg. Because of extensive metabolism, only 2.2 mg of physostigmine were detected systemically. 5 After removing the PTS, the mean apparent half-life of elimination was 4.9 h, compared with 0.5 h for the i.v. infusion. This indicates continued drug absorption from a skin depot. 6 Physostigmine was well tolerated by the volunteers. With the PTS, a mild erythema was observed at the area of application, disappearing within a few hours.

The bioavailability and bioequivalence of two different film coated tablets containing ethinylestradiol (CAS 57-63-6) and chlormadinone acetate (CAS 302-22-7) (Bellissima as test and the respective preparation from the originator as reference) were investigated in 20 healthy female volunteers after oral single-dose administration. The study was performed according to a single-center, randomised, single-dose, 2-way cross-over design with a wash-out phase of 28 days. Blood samples for pharmacokinetic profiling were taken up to 168 h post-dose, and ethinylestradiol and chlormadinone acetate plasma concentrations were determined with a validated LC-MS/MS method. The observed mean maximum plasma concentrations (Cmax) of ethinylestradiol were 124.96 pg/ml (test) and 129.12 pg/ml (reference). In the case of chlormadinone acetate, Cmax averaged 6.9566 ng/ml (test) and 6.6663 ng/m (reference). The geometric means of area under the plasma concentration-time curve (AUC(0-infinity)) of ethinylestradiol were 1292.35 pg/ml x h (test) and 1380.49 pg/ml x h (reference). For chlormadinone acetate, geometric means of AUC(0-infinity) were 53.322 ng/ml x h (test) and 58.111 ng/ml x h (reference). The median of tmax of ethinylestradiol was 1.5 h for both test and reference and the median of tmax of chlormadinone acetate 1.0 h (test) and 1.5 h (reference). Plasma elimination half-lives (t1/2) of ethinylestradiol were 14.96 h (test) and 15.41 h (reference) and of chlormadinone acetate 56.63 h (test) and 56.17 h (reference), respectively. Both primary target parameters AUC(0-infinity) and Cmax were tested parametrically by analysis of variance (ANOVA). The point estimator and the 90% confidence intervals for the AUC(0-infinity) ratio (test/reference: 93.72% [86.62%-101.39%]) indicate high similarity of both formulations with respect to the extent of ethinylestradiol exposure. A high degree of similarity was also observed for Cmax of ethinylestradiol, as the point estimator and the 90% confidence interval for the Cmax ratio are 96.18% (90.82%-101.86%). Regarding the AUC(0-infinity) ratio of chlormadinone acetate, the point estimator is 91.60% and the 90% confidence interval 84.08%-99.79%. Furthermore, exchangeability of both formulations is also suggested by the point estimator and 90% confidence of Cmax of this active agent (104.72% [95.76%-114.53%]). Bioequivalence between test and reference formulation was demonstrated since for both ethinylestradiol and chlormadinone acetate all 90% confidence intervals of AUC(0-infinity) and Cmax fall into the generally accepted range of 80%-125%.

In this study bioequivalence could be demonstrated with respect to rate and extent of methocarbamol exposure.