Inhibition of luteal phase progesterone levels in the rhesus monkey by epostane.

This study examined the effect of epostane, a new antifertility drug, on normal and hCG-stimulated progesterone production during the luteal phase of the menstrual cycle in rhesus monkeys. When administered once each day for five days, epostane inhibited normal luteal phase progesterone levels in a dose-related fashion. Epostane also reduced the elevated luteal phase progesterone levels of animals treated with hCG indicating that the drug acts directly on the corpus luteum. These data suggest that epostane interferes with corpus luteum function in a primate and that the drug would be effective as an interceptive agent during early pregnancy.