Category: Pharmacology & Therapeutics
Keywords: contraception (PubMed Search)
Posted: 5/11/2023 by Ashley Martinelli
(Updated: 12/26/2024)
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Emergency contraception is highly effective at preventing unwanted pregnancies and has been on the market for 20+ years.
Levonogestrel (LNG) 1.5 mg PO x 1 dose (OTC Available)
Ulipristal acetate (UPA) 30 mg PO x 1 dose (Requires RX)
Original studies with LNG was estimated to prevent up to 80% of expected pregnancies. In the subsequent trials that brought UPA to the market and compared the two medications, LNG prevented 69% (95% CI, 46-82%) and 52.2% (95% CI, 25.1-69.5%).
While pregnancy rates are low with both options there is concern with patients of higher weight/BMI that the effectiveness of levonorgestrel decreases as weight rises. One large study of over 1700 patients specifically noted that a weight > 75 kg was associated with up to 6.5% pregnancy rate (95% CI 3.1-11.5) compared to 1.4% (95% CI 0.5-3.0) in patients weighing 65-75 kg. Patients weighing > 85 kg had similarly high rates at 5.7% (95% CI 2.9-10.0).
The cost difference is minimal between products, especially when considering costs associated with treatment failures and subsequent need for care- the largest difference is with respect to access as LNG is OTC and UPA requires an RX. Either can be administered in an ED setting as long as they are on formulary.
ACOG also recommends that ulipristal be utilized for it higher overall efficacy compared to levonorgestrel.
Consider:
For patients above 75 kg, ulipristal can be used as first line emergency contraception for up to 5 days following unprotected intercourse.
Patients < 75 kg and < 72 hours following unprotected intercourse can use levonorgestrel or ulipristal as an appropriate emergency contraception method.
Patients < 75 kg and 72-120 hours following unprotected intercourse should use ulipristal due to its efficacy beyond 72 hours.
Kapp N, Abitbol JL, Mathe H, et al. Effect of body weight and BMI on the efficacy of levonogestrel emergency contraception. Contraception. 2015;91(2):97-104.
Emergency contraception. Practice Bulletin No. 152. American College of Obstetricians and Gynecologists. Obstet Gynecol 2015;126:e1–11
