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%.

The two types of estradiol transdermal patches were equivalent in providing an effective and rapid relief from climacteric symptoms. Systemically both patches were fairly well tolerated. The SAM patches were significantly better tolerated by the skin. The better local tolerability combined with better adhesion and cosmetic properties render the SAM patches very patient friendly and improve the compliance in the long term estrogen replacement therapy required to reduce osteoporosis and cardiovascular risks.

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