[Contraceptive activity and mechanism of action of combinations of a new 17 alpha-acetoxyprogesterone derivative and ethinyl estradiol].

It was shown in experiments on rats and rabbits that a new derivative of 17 alpha-acetoxyprogesterone--mepregnol diacetate--combined with ethinyl estradiol in varied doses and ratios elicits a pronounced contraceptive effect. This steroid combination exerts neither antigonadotropic nor antiovulatory action. The changes detected in the RNA content are apparently of importance in the mechanism of the drug effect on reproduction. A role has been demonstrated of the central cholino- and adrenoreactive systems in providing the contraceptive effect of decreased doses of ethinyl estradiol and mepregnole diacetate.