Effect of diazepam and phenobarbital sodium on postcoital contraceptive efficacy of ethinyl estradiol in rats

Abstract

Diazepam, a well known tranquilizer, and ethinyl estradiol have frequently been prescribed together in rape cases. These two drugs were reported to possess an opposite action on uterine motility. Phenobarbital, a typical enzyme inducer, has been prescribed together with ethinyl estradiol in some cases as a sedative-hypnotic. The present study was, therefore, designed to investigate the possible interferences of diazepam or phenobarbital sodium on postcoital contraceptive efficacy of ethinyl estradiol (4 μg/kg/day) in rats. All tested doses of diazepam (1, 2 and 4 mg/kg/day) or phenobarbital sodium (30 and 60 mg/kg/day) appear to have no effect on the efficacy of ethinyl estradiol when either of them was administered from D 3 to D 5 or from D 1 to D 5 of pregnancy. In addition, neither diazepam nor phenobarbital sodium at the highest doses used showed an effect on pregnancy. © 1986.