Levonorgestrel for Postcoital Contraception
Abstract & commentary
Synopsis: High-dose levonorgestrel pills are excellent for emergency postcoital contraception, but not for long-term regular contraception.
Source: World Health Organization. Contraception 2000;61:303-308.
The world health organization (who) studied efficacy and side effects of repeated postcoital administration of levonorgestrel 0.75 mg used intentionally for long-term contraception. In this study, 295 women were enrolled in six sites throughout the world. The requirement of the study was low coital frequency, 1-4 times per month. One tablet of 0.75 mg levonorgestrel was taken orally as soon as possible, but no later than one hour after each act of intercourse. Over a time period of approximately six months, the pregnancy rate was 6.8 pregnancies per 100 women-years of use (The Pearl Index). About one-third of the participants discontinued the study within six months, mainly because of bleeding problems. Menstrual complaints were reported by 70% of the women. The WHO concluded that repeated postcoital use of levonorgestrel is not a good option for regular contraception.
Comment by Leon Speroff, MD
There has been long-standing interest in developing a method of contraception that could be used intermittently and postcoitally. To date, no such method has been developed. High-dose levonorgestrel is obviously not acceptable because of the high pregnancy rate and the high percentage of menstrual irregularity.
This study of high-dose levonorgestrel for long-term contraception does not detract from the successful use of levonorgestrel as an emergency postcoital contraceptive. For this purpose, levonorgestrel 0.75 mg is given twice, 12 hours apart. The levonorgestrel method of emergency contraception is more successful and better tolerated than the combination oral contraception method.1 This high dose of levonorgestrel is available in a commercial package called "Plan B." In the worldwide study conducted by WHO, the risk of pregnancy was 60% lower with the levonorgestrel-only method compared with the oral contraceptive method.
More frequent use of emergency postcoital contraception is an effective way to reduce the number of induced abortions in the United States. Unfortunately, despite recent publicity, we still have not attained sufficient widespread knowledge and availability of this method. Information for patients and clinicians, including the latest available products, can be obtained from the following website and hotline, maintained by the Office of Population Research at Princeton University http://opr.princeton.edu/ec/. The telephone hotline number is 1-888-668-2528.
Part of the difficulty in promoting this method has been resistance on the part of those who believe that this method is aborting pregnancies already in place. Although the mechanism of action is not known with certainty, it is believed with justification that this treatment is mainly a delay of ovulation.2
Keep in mind that data from the WHO studies support the importance of timing of administration. There is a reduction in efficacy after 72 hours, and the greatest protection occurs when the medication is taken within 24 hours of intercourse. Postponing the dose by 12 hours raises the chance of pregnancy by almost 50%. For this reason, the most effective use of this method would be making it available to the patient ahead of time. Proper instruction and provision of the medication to patients to keep in reserve are strongly recommended.
References
1. Task Force on Postovulatory Methods of Fertility Regulation. Lancet 1998;352:428-433.
2. Trussell J, Raymond EG. Obstet Gynecol 1999;93:872.
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