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

In view of our previous studies that the plasma elimination of norethisterone (NET) from mini pill is faster in low socio-economic group Indian women, the present studies were contemplated to find the least effective dosage of NET from combination pills. Pharmacokinetics of NET were evaluated in a total of twenty women of low socio-economic group taking pills containing NET-acetate (500 micrograms or 1 mg) and ethinyl estradiol (30 or 50 micrograms respectively) on empty stomach. Blood samples were drawn at different time intervals from 0.5 to 24 hr and plasma NET was estimated by a specific radio-immunoassay. In the women taking 1 mg NET-acetate containing pills peak plasma levels ranging from 6.2 to 20.8 ng/ml were observed at 1 hr whereas with 500 micrograms pill they ranged from 2.0 to 6.5 ng/ml and the peak was noted at 4 hr. Pharmacokinetic parameters of NET were more or less comparable between the two pills. The results suggest that pills containing 500 micrograms NET-acetate and 30 micrograms ethinyl estradiol provide adequate levels of NET even in low-socio-economic group women.