A prospective, multicenter, open-label study conducted at 45 Planned Parenthood clinics in the U.S. assessed the efficacy of ulipristal acetate as emergency contraception (EC). Women aged 18 and above with regular menstrual cycles were eligible, provided they were not using hormonal contraceptives and agreed to use barrier methods until the study's completion. Exclusions included pregnancy, breastfeeding, IUD use, and ambiguous menstrual history.
Participants underwent a high-sensitivity urine pregnancy test at baseline, with blood samples taken for serum human chorionic gonadotropin (β-hCG) tests to exclude pre-existing pregnancies. Daily diaries were maintained to record intercourse, contraception use, intermenstrual bleeding, medication use, and adverse effects (AEs).
Pregnancy tests were conducted at enrollment, five to seven days post expected menses onset, and, if necessary, 12 to 14 days post expected menses onset. Positive results were verified by serum β-hCG tests. The study's primary efficacy endpoint was the pregnancy rate post ulipristal acetate administration.
Of 1,241 women in the primary efficacy population, 26 pregnancies occurred, resulting in a 2.1% pregnancy rate, significantly lower than the 5.5% expected rate without EC. The study confirmed ulipristal acetate's efficacy, with a 62.3% pregnancy prevention rate.
A randomized, multicenter, multinational, single-blind, non-inferiority trial compared ulipristal acetate with levonorgestrel across 35 family-planning clinics in the U.K., Ireland, and the U.S. Women requesting EC within 120 hours of unprotected intercourse were eligible, with exclusions similar to the U.S. study.
Participants were assigned to receive either levonorgestrel or ulipristal acetate, with follow-up evaluations scheduled post expected menses onset. The primary efficacy endpoint was the pregnancy rate within 72 hours of unprotected intercourse.
In the efficacy-evaluable population, 37 pregnancies occurred within 72 hours of unprotected intercourse, with ulipristal acetate showing a 1.8% pregnancy rate compared to levonorgestrel's 2.6%. The study concluded that ulipristal acetate was non-inferior to levonorgestrel, with a similar safety profile and efficacy in preventing pregnancies when administered within 48 to 120 hours after unprotected intercourse.