A COMPARISON OF THE ANTIFERTILITY AND HORMONAL ACTIVITIES OF SOME NEW SYNTHETIC OESTROGENS

Abstract

ABSTRACT The oestrogenic and post-coital antifertility activities of fourteen new synthetic steroids have been compared in the mouse and rat. The uterotrophic and post-coital antifertility potencies did not exactly parallel each other in either species. Maximum activity was found to reside in different compounds in the two species. The optimal day for prevention of pregnancy by administration of a single dose of BDH 2700 (17α-chloroethynyl-3,17β-dimethoxy-oestra1,3,5(10)-triene), a representative member of the series, was the third or fourth day of pregnancy in the mouse and the fourth day in the rat. The minimum completely effective dose was 90 μg/kg in the mouse and 810 μg/kg in the rat. The post-coital antifertility activity of BDH 2700 in the rat has been demonstrated as resulting from an increase in the rate of egg transport with their eventual expulsion through the vagina.