The research focused on a long-standing concern that emergency contraception may be less effective in people with higher BMI. While earlier work suggested that weight might influence the pharmacokinetics of UPA, this is the first trial to directly compare the biological response to both standard and double doses of the medication in individuals with obesity.
The study enrolled 52 ovulatory participants with a BMI above 30 kg/m² and a weight over 80 kg. Each participant completed two monitored cycles—receiving a 30 mg dose during one cycle and a 60 mg dose during another. Ultrasound monitoring and hormone testing were performed to track the growth and rupture of the dominant follicle, with the primary endpoint being whether ovulation was delayed for at least five days.
A control group of 12 participants with normal BMI received only the standard 30 mg dose for comparison. Blood samples were also analyzed to assess levels of UPA and its active metabolite, N-monodemethyl UPA.
The study led to the following notable findings:
- All control participants had a delay of at least five days in follicle rupture after receiving the 30 mg dose.
- Among individuals with obesity, 96% of cycles with the 30 mg dose and 91% with the 60 mg dose showed no follicle rupture within five days.
- When cycles dosed after the LH surge were excluded, every participant experienced at least a five-day delay at both dosage levels.
- Pharmacokinetic analysis showed that the 60 mg dose resulted in higher drug concentrations, but this did not lead to better pharmacodynamic outcomes compared with the standard 30 mg dose.
The authors emphasize that these findings fill a major evidence gap. Although earlier studies had raised concerns about reduced effectiveness in people with higher BMI, this trial shows that UPA’s ovulation-delaying effect remains consistent across weight categories. The standard 30 mg dose produced reliable suppression of follicle rupture when administered before the LH surge.
The study also contextualizes these results within existing emergency contraception research. While levonorgestrel-based emergency contraception may be less effective at higher body weights, UPA does not show the same pattern. The authors note that ovulation delay is a valid surrogate marker, as pregnancy cannot occur without ovulation, and therefore, the pharmacodynamic findings strongly support the continued use of the standard dose.
The researchers acknowledge limitations, including reliance on surrogate outcomes, early termination of enrollment due to the COVID-19 pandemic, and the lack of blinding, which might have influenced pharmacokinetic comparisons. However, the consistency of ovulation delay across all participants strengthens the overall message.
The study concludes that increasing the dose of UPA offers no additional benefit, reinforcing that the standard 30 mg should remain the recommended dose for emergency contraception—regardless of a person’s BMI or body weight.
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