Effects of a sequential regimen of mifepristone-medroxyprogesterone acetate on ovarian function, endometrial development and hormonal parameters.

Abstract The efficacy of a low dose of mifepristone, 5 mg/day for the first 15 days of the menstrual cycle, followed by medroxyprogesterone acetate (MPA), 10 mg/day for the next 13 days, for inhibiting ovulation was assessed in ten volunteers who were treated for three successive cycles. Hormonal determinations in blood and urine samples, ovarian ultrasonography and an endometrial biopsy taken on day 21–24 of the third treatment cycle were used to monitor the cycles. Ovulation was confirmed in 11 of the 30 treated cycles and, in these 11, the LH peak and follicular rupture occurred during MPA treatment periods. Out of 19 anovulatory cycles, 16 had no increase in progesterone levels and another 3 developed a luteinized unruptured follicle. Progestin administration induced secretory changes in the endometrium, but irregular or delayed development was found. Regular withdrawal bleeding occurred in all subjects. These data indicate that the sequential regimen can suppress ovulation while maintaining regular bleeding but increased efficacy is needed for phase II clinical trials.