Adding a COX Inhibitor Might Improve the Efficacy of Emergency Contraception

16 Sept 2023 • A single 40-mg dose of piroxicam added to levonorgestrel resulted in a lower pregnancy rate than did levonorgestrel alone. Cyclo-oxygenase (COX) inhibitors - generally used as nonsteroidal anti-inflammatory drugs (NSAIDs) - also disrupt ovulation, but their ability to prevent pregnancy has not been studied previously.

Researchers in Hong Kong randomized 860 healthy women who requested emergency contraception to 1.5-mg levonorgestrel plus 40-mg piroxicam (a COX inhibitor with a half-life of ≈50 hours) or to levonorgestrel plus placebo. Mean time between unprotected sexual intercourse and emergency contraception use was 18 hours. Women using hormonal contraception were excluded from this study.

Key results were as follows:

  • Seven pregnancies occurred in the levonorgestrel-alone group (1.7%), and one occurred in the combined levonorgestrel/piroxicam group (0.2%).
  • Compared with the number of pregnancies expected without emergency contraception (19 in each group), 63% fewer pregnancies occurred with levonorgestrel alone, and 95% fewer occurred with levonorgestrel/piroxicam.
  • Side effects (e.g., nausea, fatigue) were similar between groups.

Oral piroxicam 40 mg co-administered with levonorgestrel improved efficacy of EC in the above study. Piroxicam co-administration could be considered clinically where levonorgestrel EC is the option of choice.

Source: NEJM | Read full story

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