Objective: To determine the contraceptive efficacy of a low-dose combined oral contraceptive containing ethinyloestradiol (EE) 20 μg/drospirenone (drsp) 3mg administered for 24 days followed by a four-day hormone-free interval (24/4 regimen), by pooling data from four clinical trials.
Study design: Data on the occurrence of pregnancy during treatment in four open-label trials that enrolled healthy female volunteers aged 17-36 years, who received EE 20 μg/drsp 3mg in a 24/4 regimen for 7 or 13 cycles, were pooled.
Results: Sixteen pregnancies occurred among 2386 women during 729,537 days (26,055 cycles) of treatment exposure, resulting in a Pearl Index (PI) of 0.80 (upper two-sided 95% confidence interval (CI) limit of 1.30). Of these pregnancies, seven were defined as method failures, resulting in an adjusted PI of 0.41 (upper two-sided 95% CI limit of 0.85), based on 616,607 days (22,022 cycles) of treatment. The Kaplan-Meier estimate for the one-year cumulative probability of contraceptive protection was 99.21%.
Conclusions: The EE 20 μg/drsp 3mg combined oral contraceptive administered in a 24/4 regimen has acceptable contraceptive efficacy.
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