Fertility in the rhesus monkey following long-term inhibition of ovarian function with danazol

Danazol was previously reported to be an oral contraceptive in the rhesus monkey at doses of 200 and 400 mg/monkey/day for 90 days. The drug is now shown to be an effective long-term inhibitor of ovarian function in the monkey. In the final 3 months of a 27-month period of treatment at a dose of 400 mg/monkey/day, the drug continued to be an effective oral contraceptive. During the 27-month treatment period, three of seven monkeys were amenorrheic and the remaining had only 16 of the 109 expected menstrual cycles. Following the discontinuation of medication, all seven monkeys conceived within 2 to 6 weeks. One monkey aborted early in pregnancy and the remaining six delivered normal, healthy infants at term. Therefore, following the discontinuation of long-term treatment with danazol in the monkey, there was rapid and complete return of normal ovarian function.