Biological evaluation of mibolerone in the female Beagle.

Mibolerone effectively inhibited estrous activity in immature or mature Beagle bitches given 60 and 200 microgram, respectively, daily for up to 730 days. A dose level of 20 microgram of mibolerone daily was 70% effective in preventing estrus. Effects of mibolerone included estrus inhibition prolongation of the interestrous interval in bitches given 20 microgram of the mibolerone daily, vaginal discharge, and a dose-related increase in clitoral size. A decrease in posttreatment conception rate was observed only in bitches receiving 20 microgram of mibolerone daily for 730 days. Pups born to bitches conceiving after mibolerone treatment were grossly normal.