Objective: To compare the effects on ovarian activity of two oral contraceptives containing nomegestrol acetate (NOMAC)/17 beta-oestradiol (E2) or drospirenone (DRSP)/ethinylestradiol (EE).
Methods: In this open-label, randomised, six-cycle study, 32 subjects using NOMAC/E2 (2.5-1.5 mg; 24/4-day regimen) were compared to 16 subjects using DRSP/EE (3 mg-30 microg; 21/7-day regimen). Measurements included serum oestradiol, progesterone, follicle stimulating hormone (FSH) and luteinising hormone (LH), and ultrasonography of follicular diameter.
Results: No ovulations occurred during treatment. Progesterone was fully suppressed, with mean maximum values <2 nmol/l in both groups over all cycles. For NOMAC/E2, mean maximum follicular diameter decreased from 19.3 mm before treatment to between 6.9 and 8.2 mm during treatment, with no subject having a follicular diameter ≥15 mm. For DRSP/EE, a decrease from 19.6 to between 7.4 and 10.8 mm was observed, with two subjects (12.5%) having a maximum follicle diameter ≥15 mm. These findings were consistent with observed FSH reductions; full suppression of LH surges was observed in both groups. Post-treatment return of ovulation in both groups occurred on average 21 days after the last active tablet intake.
Conclusions: NOMAC/E2 achieves consistent ovulation inhibition, with suppressive effects on the ovaries at least similar to those of DRSP/EE.