Bio-availability and pharmacokinetics of cyproterone acetate- 14C and ethinyloestradiol- 3H after oral administration as a coated tablet (SH B 209 AB)

Abstract

Eight young women were each given 2 mg cyproterone acetate-methyle-ne- 14C and 50 μg ethinyloestradiol-6,7- 3H, ingredients of the contraceptive SH B 209 AB, orally in coated tablet form. The 14C and 3H activity in plasma, urine and faeces was determined up to 7 or 10 days post-administration. Cyproterone acetate was absorbed completely. The maximum plasma level was reached between 30 minutes and 3 hours after administration. At this time 2.2 ± 0.6 % of the dose was found in total plasma, which corresponds to 24 ± 6 ng cyproterone acetate equivalents/ml. At first the plasma level decreased with a half-life of 7.9 ± 1.3 hr (distribution and elimination) and later with a half-life of 2.5±0.6 d (elimination). Elimination via urine was 37 ± 5%. Up to the 10th day after administration 91±2 % of the dose had been found in urine and faeces. Ethinyloestradiol was absorbed very rapidly and almost completely. The maximum plasma level was reached only 60 ± 30 minutes after administration. At this time 10 ± 2% of the dose could be found in the plasma, which corresponds to 2.1 ± 0.5 ng ethinyloestradiol equivalents/ml. Due to processes of distribution and elimination, the plasma level dropped up to about 8 hr post-administration with a half-life of 5.1±1.5 hr, later with a half-life of 27 ± 8 hr, corresponding to the rate of elimination. Ethinyloestradiol was eliminated in urine and faeces in the ratio 4: 6. 91 ± 9 % of the dose could be recovered in this investigation.