A randomized crossover trial conducted at Oregon Health & Science University and Eastern Virginia Medical School from June 2017 to November 2021 has demonstrated that ulipristal acetate emergency contraception effectively delays ovulation across all body mass index groups.
The study, published in BMJ Sexual & Reproductive Health, enrolled 52 participants with a body mass index (BMI) greater than 30 kg/m² and weight greater than 80 kg, and 12 controls with a BMI less than 25 kg/m². The trial design included three menstrual cycles for the high-BMI group: two treatment cycles (cycles 1 and 3) separated by a washout cycle. During treatment cycles, participants received either 30 mg or 60 mg of UPA, while control participants underwent only one treatment cycle with 30 mg UPA.
The primary outcome, the proportion of cycles without follicle rupture 5 days post-UPA dosing, was similar between the 30 mg and 60 mg doses in the high-BMI cohort (96% and 91%, respectively, p=0.43). All control participants (100%) achieved at least a 5-day ovulation delay. Notably, when excluding cycles where dosing occurred after the luteinizing hormone (LH) surge, all participants in both dosing groups experienced at least a 5-day delay in ovulation.
Pharmacokinetic analysis revealed that exposures of UPA were approximately twofold higher in the BMI >30 kg/m² cohort compared with the control BMI cohort at the 30 mg dose. The 60 mg dose resulted in proportionally higher exposures. The apparent oral clearance of UPA was observed to be approximately twofold lower in the BMI >30 kg/m² cohort compared with the normal BMI cohort. Similar findings were noted for UPA's active metabolite, N-monodemethyl-UPA.
The study faced several limitations, including the lack of baseline follicular monitoring beyond a single progesterone level and the impact of the COVID-19 pandemic, which led to stopping enrollment at 64 participants (9 fewer than the estimated sample size). Additionally, the study design did not mask UPA dosing to preserve pharmacokinetic accuracy.
These findings demonstrate that the standard 30 mg dose of UPA effectively delays ovulation regardless of BMI or weight. The data suggest that dose adjustment may not be necessary for participants with obesity, providing evidence that UPA emergency contraception maintains consistent efficacy across BMI groups without requiring weight-based modifications.
Full disclosures and funding information can be found in the published study.
