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[Bioavailability and pharmacokinetics of 14C-cyproterone acetate after administration as a 50-mg tablet (author's
Abstract:
Four male volunteers were each given a 50 mg oral dose of methylene-14C-labelled cyproterone acetate in a formulation largely identical to the commercial preparation Androcur Tablets. A further 3 volunteers were each given 10 mg of the 14C-labelled compound by intramuscular injection. Plasma samples were obtained and urine and faeces collected quantitatively from each volunteer up to 10 days post administration. 1. Absorption of the 50 mg of cyproterone acetate administered in the form of Androcur Tablets was largely complete. 2. The maximal plasma level of 400 +/- 40 ng cyproterone acetate equivalents/ml of plasma, calculated from the 14C activity, was found 3,8 +/- 0,5 hours after oral administration. By 10 hours post administration the plasma level had declined with a half-life of 7,9 +/- 2,5 hours (distribution and elimination). The fictitious distribution volume assignable to this process amounted to 140 +/- 40% of body weight. Plasma 14C-activity then decreased with a half-life of 1,8 +/- 0,2 days, which was consistent with elimination. 3. The labelled substance was almost completely extractable from plasma and could be separated by chromatography into 2 fractions of about equal size: cyproterone acetate and one metabolite. 4. Orally administered cyproterone acetate was eliminated with a half-life of 1,6 +/- 0,1 days. By 10 days post administration 33 +/- 6% of the dose had been detected in urine and 60 +/- 8% in faeces. Up to this time total elimination amounted to 93 +/- 5% of the dose. 5. After intramuscular injection of 10 mg of cyproterone acetate the half-life for absorption from the muscular depot was 7,0 +/- 0,2 hours. Between 2 and 10 days post administration there was a uniform decrease in plasma level and urinary elimination with half-life of 2,3 +/- 0,1 days and 2,1 +/- 0,2 days respectively. By the end of the trial 34 +/- 5% of the dose had been eliminated with urine and 57 +/- 6% with faeces.