A randomised study comparing a low dose of mifepristone and the Yuzpe regimen for emergency contraception

Objective To compare 100 mg mifepristone with the standard Yuzpe regimen for emergency contraception.

Design Randomised controlled trial.

Setting Family Planning Clinic, Aberdeen.

Sample One thousand women seeking emergency contraception within 72 hours after an episode of unprotected sexual intercourse.

Methods Women were randomised to receive either 100 mg (half tablet) of mifepristone as a single dose or the Yuzpe regimen (two tablets each with 50 mug ethinyloestradiol and 0.25 mg levonorgestrel, to be repeated 12 hours later).

Outcome measures Crude pregnancy rates, proportion of pregnancies prevented, side effects and patient acceptability.

Results The crude pregnancy rates (95% CI) for the Yuzpe regimen and mifepristone were 3.6% (2.3-5.7) and 0.6% (0.2-1.8), respectively, with a significant difference between the two groups (RR 6.04; 95% CI 1.75-20.75). Mifepristone prevented 92% of pregnancies and the Yuzpe regimen preventing 56%. An increasing coitus to treatment interval was associated with contraceptive failure in the Yuzpe group (P = 0.03) with no association seen with mifepristone. Following administration of mifepristone 24.5% and 13.1% given the Yuzpe regimen had a delayed period (RR 2.14; 95% CI 1.46-3.15). Overall, mifepristone was better tolerated than the Yuzpe regimen with significantly fewer side effects. More women were satisfied (P < 0.0001) with mifepristone as an emergency contraceptive and would recommend it to a friend (P = 0.02).

Conclusion Mifepristone administered in a 100 mg dose is a highly effective post-coital contraceptive with high patient acceptability and fewer side effects compared with the standard Yuzpe regimen. Delay in the onset of menstruation did not decrease patient acceptability.