Phase 3 Study of Desogestrel and Ethinyl Estradiol Combined Oral Contraceptive for Pregnancy Prevention

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INTRODUCTION: Substituting low-dose ethinyl estradiol for the typical hormone-free interval in combined oral contraceptives may enhance ovarian suppression and improve tolerability. This phase 3 study evaluated the efficacy and safety of a 28-day combined oral contraceptive regimen including 21 days of desogestrel and ethinyl estradiol followed by 7 days of ethinyl estradiol. METHODS: This was a multicenter, open-label, phase 3, single-arm study that enrolled sexually active women 18–40 years old at risk for pregnancy. Women received up to 1 year, or 13 consecutive 28-day cycles, of 150 micrograms desogestrel and 20 micrograms ethinyl estradiol for 21 days and 10 micrograms ethinyl estradiol alone for 7 days. Patients kept diaries to record compliance, bleeding or spotting, and other contraceptive use. Efficacy was measured using the Pearl Index and life table approach. Safety and tolerability were assessed through reported adverse events. RESULTS: A total of 2,858 women were enrolled and 1,680 completed the study. Forty-six pregnancies in 2,401 women aged 18–35 years occurred after combined oral contraception initiation and up to 7 days after the last desogestrel and ethinyl estradiol or ethinyl estradiol-only tablet was taken. When cycles in which another birth control method was used were excluded, the Pearl Index was 2.68 (95% confidence interval [CI] 1.96–3.57). The life table pregnancy rate was 2.47% (95% CI 1.85%–3.29%) for all users aged 18–35 years. When only cycles during which women considered compliant were included, the Pearl Index was 2.00 (95% CI 1.39–2.80). Adverse events were similar to those seen with other oral contraceptives. CONCLUSIONS: This 28-day desogestrel and ethinyl estradiol combined oral contraceptive, including 7 days of low-dose ethinyl estradiol, was efficacious and well tolerated for pregnancy prevention.