Objective: To compare the efficacy, side effects and the effect on next menstruation of levonorgestrel(LNG) to low dose mifepristone in emergency contraception.
Methods: The study is a randomized double-blind multicenter comparative trial. The clients who have unprotected intercourse within 72 hours were allocated to one of the two study groups. In LNG group, 0.75 mg LNG was taken twice with 12 hours apart. In mifepristone (Mife-) group, single dose of 10 mg mifepristone was taken and a placebo 12 hours after. Follow-up visit was paid on the seventh day of the expected next menstruation to evaluate the contraceptive efficacy and to record side effects and menstruation. Contraceptive efficacy was calculated by Dixon's method.
Results: The total valid subjects in LNG and Mife- group were 643 and 633, respectively. There were 20 and 9 pregnancies occurred respectively in each group. The failure rate was 3.1% and 1.4%. Contraceptive efficacy rate of preventing pregnancy was 59.2% and 79.7%, the difference was statistically significant (P < 0.05). The incidence of various side effects was less than 10.0% which were mild. There was no statistically difference between the two groups. The percentage of subjects who had their next menstruation before or after their expected menstruation 3 days in LNG group and Mife- group was 77.7% and 78.5% respectively. The menstrual period less than 7 days was 95.0% and 93.3%.
Conclusion: Use of levonorgestrel or low dose mifepristone for emergency contraception is effective and safe.