Transfer of cyproterone acetate to the milk of lactating women.

Cyproterone acetate (CPA) was administered in a dose of 50 mg to 6 lactating women delivered by caesarean section. All women had to discontinue breast feeding the day before treatment. Prior to, and 3 and 9 hours after ingestion of the drug, plasma and milk specimens were taken. Total daily milk volume was recorded. Concentration of CPA in plasma and milk was determined by RIA. The plasma levels of CPA were in the range of 65 - 450 ng/ml at 3 h and 76 - 270 ng/ml after 9 hours. The respective concentrations in milk were 16 - 260 ng/ml (3 h) and 55 - 130 ng/ml (9 h). The plasma/milk ratio of drug concentration varied between 1.1 and 9.3 (3 h) and 0.6 and 2.9 (9 h). The mean of all values amounted to 2.8 +/- 2.3. Taking into account a daily milk production of 1050 +/- 230 ml, 0.2% of the dose administered (range: 0.06 - 0.41 % of dose) would have been transferred to the newborn. Use of the CPA-containing oral contraceptive DIANER (2 mg of CPA + 50 microgram of ethinyl estradiol) by nursing women would therefore result in the transfer of 1 microgram/kg to the child.