Pharmacokinetics of norethisterone from two different combination contraceptive pills in Indian women.

ABSTRACT

PIP: In view of the previous studies that determined that the plasma elimination of norethisterone (NET) from the minipill is faster in low socioeconomic bracket Indian women, the present studies were undertaken to find the least effective dosage of NET from combination pills. Pharmacokinetics of NET were evaluated in a total of 20 low socioeconomic women who were taking pills containing NET-acetate (500 mcg or 1 mg) and ethinyl estradiol (30 or 50 mcg respectively) on empty stomachs. Blood samples were drawn at different time intervals from 0.5-24 hours and plasma NET was estimated by a specific radioimmunoassay. In the women taking 1 mg NET-acetate containing pills peak plasma levels ranging from 6.2-20.8 ng/ml were observed at 1 hour whereas with the 500 mcg pills, they ranged from 2.0-6.5 ng/ml and the peak was noted at 4 hours. Pharmacokinetic parameters of NET were more or less comparable between the 2 pills. The results suggest that pills containing 500 mcg NET-acetate and 30 mcg ethinyl estradiol provide adequate levels of NET even among low socioeconomic women.