Objective: To investigate ovulation inhibition with drospirenone, a novel progestogen that has a profile similar to natural progesterone, when given alone or in combination with ethinylestradiol.

Method: Hormonal parameters (LH, FSH, 17beta-estradiol and progesterone) and peripheral parameters (cervical score, spinnbarkeit and crystallization), as well as follicle size assessed by ultrasonography, were measured in two groups of healthy women. Forty-eight women aged 19-35 years were randomly assigned to receive 0.5 mg, 1.0 mg, 2.0 mg or 3.0 mg of drospirenone over a single treatment cycle, and 52 women aged 20-35 years were randomized to receive either 2 mg drospirenone/30 microg ethinylestradiol or 3 mg drospirenone/30 microg ethinylestradiol over three treatment cycles. Baseline measurements were taken during a control pretreatment cycle.

Results: Adequate ovarian suppression with drospirenone alone was evident at dose levels of 2 and 3 mg, and at 3 mg all subjects had anovulatory cycles. Although both combined preparations (2 mg and 3 mg drospirenone/30 microg ethinylestradiol) inhibited the hypothalamic-pituitary-ovarian axis, follicular maturation leading to escape ovulation was observed in three subjects in the 2 mg drospirenone/30 microg ethinylestradiol group. Only one of these ovulations was considered to be definitely the result of treatment failure. All cycles in the 3 mg drospirenone/30 microg ethinylestradiol group were anovulatory. No statistically significant difference was found between treatment groups.

Conclusion: The combination of 3 mg drospirenone/30 microg ethinylestradiol (Yasmin, Schering AG) reliably inhibits ovulation, with a low frequency of follicular maturation, and provides a reasonable safety margin.