British researchers report that mifepristone is just as effective as a "morning-after" pill as levonorgestrel when taken within 5 days of unprotected sex. In a study of 2000 women, researchers from the University of Aberdeen compared efficacy, adverse effects, and acceptability of one 10-mg dose of mifepristone with two 750-mcg doses of levonorgestrel 12 hours apart. The drugs were taken within 120 hours of unprotected sex. Failure rates were 1.5% with mifepristone and 2.3% with levonorgestrel.
The investigators reported recently in Obstetrics & Gynecology that the difference in failure rates was not necessarily statistically significant, but they considered the possibility that levonorgestrel could be less effective than mifepristone. Patient acceptability rates were also high: 94% in the mifepristone group and 91% in the levonorgestrel group. The researchers noted, however, that, since the study was conducted, the licensing of levonorgestrel has been reduced to a single-dose regimen, which should be taken into consideration when comparing the acceptability of both drugs.
Ms. Farley is a freelance medical writer based in Wakefield, RI.