Is Plan B More Effective Than Yuzpe Emergency Contraception?


Some patients report difficulty accessing emergency contraception despite its OTC availability to those of all ages across the United States.

Some patients report difficulty accessing emergency contraception (EC) despite its OTC availability to those of all ages across the United States.

Women seeking EC can take certain daily oral contraceptive pills 12 hours apart as an alternative. Effective contraceptives must include 0.1 mg ethinyl estradiol and either 0.5 mg levonorgestrel or 1 mg norgestrel to emulate the older Yuzpe method. The modified Yuzpe method is desirable because the patient doesn’t need to purchase anything if they take an appropriate oral contraceptive regularly.

Previous comparisons between levonorgestrel-based EC (Plan B)—which has become more available over time since its introduction in 1999—and the Yuzpe method have been unrealistic due to randomized controlled trials’ (RCTs) strict inclusion criteria and close monitoring. However, new study results suggest levonorgestrel-based EC is more effective than the Yuzpe method, although both methods seem less effective than previous estimates have shown.1

The retrospective and population-based study collected data from patients who presented to Canadian community pharmacies for EC. Patient medical records included self-reported timings of menses, history of unprotected intercourse, and payments for any pregnancy- or abortion-related health services.

Levonorgestrel and the Yuzpe method both reduced absolute pregnancy risk by slight margins (2.8% and 1.8%, respecvitely). Levonorgestrel prevented pregnancy more effectively than the Yuzpe method, as levonorgestrel users became pregnant 64% less often than Yuzpe method users. Yet, both groups became pregnant almost twice as often as participants in previous trials.

Women presenting to the pharmacy in real-world conditions are more likely to have had unprotected sex multiple times in the pregnancy-danger window than in the trials.

The authors assumed a high baseline risk (5%), but other studies have shown pregnancy risk without contraception below 4%. A lower baseline pregnancy risk would further diminish the EC’s real-world impact.

The World Health Organization (WHO) considers levonorgestrel regimens to be 85% effective based on RCTs. In 1998, the WHO found a 1% risk of pregnancy with levonorgestrel use and a greater disparity between the effectiveness of the 2 methods.2

Pharmacists should encourage EC seekers to use levonorgestrel products rather than emulating the older estrogen/progesterone Yuzpe method. EC’s less-than-expected effectiveness underscores the need for family planning counseling from pharmacists and other providers.


1. Leung VWY, et al. Population-based evaluation of the effectiveness of two regimens for emergency contraception. Int J Gynaecol Obstet. 2016;133(3):342-346.

2. Task Force on Postovulatory Methods of Fertility Regulation. Randomized controlled trial of levonorgestrel versus the Yuzpe regimen of combined oral contraceptives for emergency contraception. Lancet. 1998;352(9126):428-433.

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