Contraceptive potential of a mifepristone-nomegestrol acetate sequential regimen in women

The effectiveness of a sequential regimen consisting of mifepristone, 10mg/day for 15 days, followed by nomegestrol acetate (NOMA), 5 mg/day forthe next 13 days, for inhibiting ovulation and maintaining regular bleedingcycles was assessed in 10 surgically sterilized volunteers who werefollowed for one pretreatment and three treated cycles. Hormonaldeterminations in blood and urine, ovarian ultrasonography, bleedingrecords in all cycles and an endometrial biopsy taken on day 22-25 of thethird treatment cycle were used to monitor the effects of treatment. Duringtreatment, 24 monophasic (no sustained progesterone rise above 12 nmol/l)and six biphasic cycles were recorded. Nine follicular ruptures weredetected echographically in these 30 treated cycles, five of which occurredin monophasic cycles. All follicular ruptures occurred on days 1-7 of NOMAtreatment. Echographic and endocrine features of ovulatory cycles were bothpresent in only four treated cycles (13.3%). Development of a secretoryendometrium was achieved in all cases, but it was always irregular. Regularwithdrawal bleeding occurred in all subjects and no adverse reactions wererecorded. The ovarian and endometrial effects of this regimen justifytesting its contraceptive effectiveness in phase 2 clinical trials.