Emergency contraception for individuals weighing 80 kg or greater: A randomized trial of 30 mg ulipristal acetate and 1.5 mg or 3.0 mg levonorgestrel

Abstract

ObjectiveTo compare the efficacy of oral emergency contraception (EC) regimens used within 72 hours of unprotected intercourse in individuals weighing >80 kg. Study DesignWe enrolled healthy women aged 18-40 years with a weight of at least 80 kg requesting EC in a multi-center, single-blind, randomized study of levonorgestrel 1.5 mg (LNG1X) and 3.0 mg (LNG2X) and ulipristal acetate 30 mg (UPA) (enrollment goal 1200). Key eligibility requirements included regular cycles, unprotected intercourse within 72 hours of enrollment, no use of hormonal contraception since last menstrual period, a negative urine pregnancy test (UPT), and willingness to abstain from intercourse until next menses. Study staff directly observed EC ingestion. To assess our primary outcome of incidence of pregnancy, participants completed home UPTs; if no menses by 2-weeks post-treatment, or a positive UPT, they returned for an in person visit with quantitative serum human chorionic gonadotropin (hCG) and ultrasound. ResultsWe enrolled and randomized 532; 44 were not dosed or not evaluable for primary end-point, leaving an analyzable sample of 488 (173 LNG1X, 158 LNG2X, 157 UPA) with similar demographics between groups [mean age 29.6 years (5.74), BMI 37.09 kg/m2 (6.95)]. Five pregnancies occurred during the study (LNG1X n = 1, LNG2X n = 1, UPA n = 3); none occurred during the highest at-risk window relative to estimated day of ovulation (day of ovulation and the 3 days prior). We closed the study prior to achieving our enrollment goal because the low pregnancy rate in all groups established futility based on an interim blinded analysis. ConclusionAlthough slow enrollment limited our study power, we found no differences in pregnancy rates between oral EC regimens among women weighing 80 kg or more. Our results are not able to refute or support differences between the three treatment arms. ImplicationsWomen weighing 80 kg or more experienced no differences in pregnancy rates between oral EC regimens but due to several significant study limitations including sample size and the lack of a study population at high risk of pregnancy, our results are not able to determine if differences in treatment effectiveness exist.