Final Canadian Report of a Clinical Trial Evaluating the Safety and Efficacy of a New, Low-Dose Oral Contraceptive, Alesse™

Abstract

The efficacy and safety of a new, low-dose, 21-day combination oral contraceptive containing 100 μg of levonorgestrel and 20 μg of ethinyl estradiol were evaluated in an open-label, multicentre trial. A total of 254 Canadian subjects were enrolled and received 4,564 cycles of exposure over the three-year course of the study. Of these, 137 completed 18 cycles of treatment. During the total 4,482 evaluable cycles of treatment, one pregnancy occurred, for a Pearl Index of 0.29 (82 cycles were excluded from this calculation due to protocol violations, including use of a second form of contraception or missing three or more consecutive pills in a cycle). Over the course of the study, 129 subjects withdrew for any reason, including 43 (17%) due to adverse events. The cumulative failure rate by life table analysis was 0.0048 per woman entering the 14th cycle. Breakthrough bleeding alone occurred in 3.9 percent of the cycles and breakthrough bleeding and spotting occurred together in 9.6 percent of the cycles. Of evaluable cycles, 1.3 percent were amenorrhoeic. The most commonly reported adverse events in this trial considered to be at least possibly due to the test drug were headache (36%) and metrorrhagia (36%). This formulation provides contraceptive efficacy similar to higher-dose oral contraceptives, while maintaining a safety and common OC side-effect profile that is consistent with prior years of reported use with kvonmgestrel-containing products.