Suppression of ovarian function by a combined oral contraceptive containing 0.02 mg ethinyl estradiol and 2 mg chlormadinone acetate given in a 24/4-day intake regimen over three cycles.

Objective: To describe the suppression of ovarian function with 0.02 mg ethinyl E(2)-2 mg chlormadinone acetate administered in a 24/4-day intake regimen in healthy women.

Design: Open, uncontrolled, multiple dosing, phase II trial.

Setting: Single clinic.

Patient(s): Forty women treated.

Intervention(s): Treatment for up to three cycles with 0.02 mg ethinyl E(2)-2 mg chlormadinone acetate given in a 24/4-day regimen.

Main Outcome Measure(s): Assessments of ovarian function classified by the Hoogland and Skouby score, thickness of endometrium, cervical reaction, and sex hormone levels, as well as overall tolerability.

Result(s): No ovulation was observed in the per protocol set (N=36), and one in the full analysis set (N=38) after vomiting and diarrhea. Absence of ovarian activity, residual ovarian activity, and formation of a luteinized unruptured follicle were observed in 75.0%, 15.9%, and 1.1% of medication cycles, respectively. Endometrial thickness was suppressed to 4 to 5 mm compared with 10 to 12 mm without medication. Cervical reaction was negative. Hormone levels were lower with medication than without, and the medication was well tolerated. Treatment-related adverse events were typical of those associated with hormonal contraceptive use.

Conclusion(s): Follicular development, cervical reaction, and endometrial thickness were suppressed profoundly after 0.02 mg ethinyl E(2)-2 mg chlormadinone acetate administration in a 24/4-day regimen, resulting in inhibition of ovulation and unfavorable conditions for fertilization, implantation, and thus pregnancy.