[Ovulation inhibition with medrogestone administered on the 4th through the 24th day of the cycle].

Medrogestone (M) is a derivative of 17 methylprogesterone (P) used for P insufficiency at oral doses of 5 to 15 mg/day (D). We studied the ability of M to inhibit cyclic pituitary-ovarian activity when given at a dose of 10 mg/d from D4 to D24. Ten healthy Caucasian females, aged from 21 to 33, volunteered for an open 2 consecutive cycle study (cycle 1 = control, cycle 2 = M). At inclusion mean (+/- SD) cycle length was 28.6 +/- 1.9 D. Plasma LH, FSH, E2, P, were measured daily from D10 to D20 and at D22, 24, 26. During cycle 1, every subject showed an ovulatory pattern with mid cycle E2 peak (151-400 pg/ml), LH peak (12-59 mUI/ml) and luteal P rise (9.4-22.8 ng/ml). Under M ovulatory surges were suppressed in each of the 10 subjects and P remained below 0.8 ng/ml. These data show that in addition to its known progestomimetic effect, M is a potent ovulation inhibitor when given from D4 to D24 of the cycle.