A comparison of the effects of two monophasic low dose oral contraceptives on the inhibition of ovulation.

Fifty-three women were randomly allocated to one of two combined low-dose monophasic oral contraceptives (20 micrograms ethinyl estradiol with 75 micrograms gestodene or 20 micrograms ethinyl estradiol with 150 micrograms desogestrel). The ability of these formulations to inhibit ovulation was compared using hormonal parameters and ovarian ultrasound. The effects on three treated cycles were compared with pre- and post-treatment cycles. No ovulations occurred in either group during therapy. Twenty-one percent of women were observed to show some follicle-like structures accompanied by raised serum estradiol in at least one treatment cycle. No significant differences between the two preparations were demonstrated on residual ovarian function. The secretion of estradiol and progesterone was significantly reduced throughout all three treatment cycles. Mean LH and FSH concentrations were comparable with both treatments. A secondary analysis of cycle control and tolerance was undertaken. Significantly less bleeding was seen in the gestodene group during cycle 2 (p = 0.02). There were no differences between the two treatments with respect to the other cycle control parameters. Approximately half the women recorded intracyclic bleeding during the first treatment cycle. This improved during cycles 2 and 3. Both formulations were tolerated well.

RCT Entities:   Population Interventions Outcomes