Interceptive activity of azastene in rhesus monkeys.

Azastene is an orally effective "luteolytic" agent in rhesus monkeys. In nonpregnant monkeys it reverses the human chorionic gonadotropin-stimulated increase in progesterone production and delay in the onset of menstruation, and, in inseminated monkeys, it prevents pregnancy if given for 5 days beginning on day 24 of the menstrual cycle. The drug is also effective in terminating pregnancy if given for 5 days beginning on approximately day 26, day 50, or day 80 of gestation. Concurrent progesterone administration prevents the interceptive action of the drug. Although azastene inhibits gonadal and placental progesterone production, it has no effect on cortisol production in monkeys and is devoid of apparent hormonal activity.