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 microg 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.