Better Methods for Emergency Contraception

Abstract & Commentary

Synopsis: A single dose of 1.5-mg levonorgestrel and a single low dose of 10-mg mifepristone are effective methods for emergency contraception.

Source: von Hertzen H, et al. Low dose mifepristone and two regimens of levonorgestrel for emergency contraception: A WHO multicentre randomised trial. Lancet. 2002;360:1803-1810.

The world health organization conducted a randomized, double-blind trial in 15 clinics in 10 countries comparing 3 methods of emergency contraception in 4136 women. The results were as follows when each treatment was administered up to 120 hours (5 days) after unprotected coitus:

The results and side effects did not differ significantly among the 3 groups. About 1% experienced vomiting.

Comment by Leon Speroff, MD

The Yuzpe regimen for emergency contraception was established 20 years ago—2 tablets of oral contraceptives followed by 2 tablets 12 hours later. The pregnancy rate (the failure rate) of this method is about 2-3% when administered within 72 hours of unprotected coitus. This method was supplanted by a 0.75-mg dose of levonorgestrel given twice, 12 hours apart, available in the United States as "Plan B." This levonorgestrel method is more successful and better tolerated than the combination oral contraceptive method. Indeed, the risk of pregnancy is 60% lower with the levonorgestrel-only method.1 The use of mifepristone for emergency contraception has been associated with a similar reduction of dose, from 600 mg to an amazingly low dose of 10 mg.

The current, well-designed and executed large study now establishes that a single low dose of either mifepristone or levonorgestrel can provide very effective emergency contraception with few side effects. There was no evidence that treatment within 72 hours after coitus or after 72 hours had a significant effect on outcome. However, the pregnancy rate after 72 hours was 2.4% compared to 1.5% in those treated within 72 hours. In fact, those treated on day 5 had a pregnancy rate of about 5%. The clinical conclusion is apparent: Recommend emergency contraception within the 72-hour window after coitus.

The disadvantage associated with mifepristone is a delay in ovulation with a longer cycle and later return of menses in about 10% of treated women. In women who continue to have unprotected coitus, this produces a 22% higher pregnancy rate compared to women who use a contraceptive method. For practical purposes, therefore, the single-dose levonorgestrel method is preferred, providing an easier method that offers better compliance without an increase in side effects.

Emergency contraception has received the attention it deserves in the last few years. This is an important method to reduce the number of unintended pregnancies and induced abortions. The Office of Population Research at Princeton University maintains a web site (http://opr.princeton.edu/ec/) and a hot line (1-888-668-2528) for patients and clinicians. In many areas, local Planned Parenthood Clinics offer emergency contraception without physician prescriptions, and in some states, emergency contraception is available directly from pharmacists. 

Dr. Speroff is Professor of Obstetrics and Gynecology Oregon Health Sciences University, Portland.

References

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

2. Comparison of three single doses of mifepristone as emergency contraception: a randomised trial. Task Force on Postovulatory Methods of Fertility Regulation. Lancet. 1999;353:697-702.