Background: Oral contraceptives (OCs) are the most widely used method of reversible contraception. Recent alterations of the standard 28-day regimen have included shortening the traditional hormone-free interval (HFI), supplementing the HFI with low-dose estrogen, or increasing the number of active pills administered, thus extending the time between withdrawal bleeding episodes by a variable number of months. In light of these changes in regimens, clinicians may be seeking evidence that the new regimens are safe and will not result in unexpected adverse events.
Methods: We initiated a long-term extension trial to evaluate the safety of a 91-day extended-regimen OC containing 150 mcg levonorgestrel/30 mcg ethinyl estradiol (EE) for 84 days, followed by 7 days of 10 mcg EE. After participation in a 1-year, open-label, phase 3 contraceptive program, 320 women qualified for enrollment in a multicenter, nonrandomized study of 91-day extended-regimen OCs for up to 3 additional consecutive years; 116 completed the study. We evaluated incidence of reported adverse events (AEs), rates of study discontinuation, and reported bleeding patterns.
Results: Total exposure was equivalent to 8292 28-day cycles. Participants reported no thromboembolic events. Thirty-one (9.7%) women discontinued treatment due to AEs. Unscheduled bleeding and spotting diminished during the course of the trial. Overall rates of study discontinuation and incidence of AEs were consistent with those observed in the phase 3 clinical program.
Conclusion: This study demonstrated that the AE profile of the 91-day extended-regimen OC over 4 years was similar to that seen in the 1-year clinical trials, with no unexpected adverse events.