Human Reproduction, Vol. 17, No. 12, 3084-3089,
December 2002
© 2002 European Society of Human Reproduction and Embryology
A randomized double-blind comparison of two single doses of mifepristone for emergency contraception*
1 Department of Reproductive Endocrinology and 2 Computer Centre, National Research Institute for Family Planning, No.12 Da Hui Si, Beijing 100081, People's Republic of China and 3 Department of Reproductive Health and Research World Health Organization, 1211 Geneva 27, Switzerland
BACKGROUND: Previous trials have shown the potential of 10 mg of mifepristone in emergency contraception. The aim of this trial was to investigate whether 10 mg of mifepristone has the same efficacy as 25 mg. METHODS: This double-blind, randomized trial was carried out in 10 family planning institutes and hospitals in China. Women who met recruitment criteria and requested emergency contraception within 120 h of a single act of unprotected coitus were randomized using a computer-generated list to either 10 or 25 mg of mifepristone within each centre. RESULTS: Among 3052 women enrolled, the outcome was known for 3030 women, 1516 in the 10 mg group and 1514 in the 25 mg group. Seventeen pregnancies occurred in each group, giving a pregnancy rate of 1.1%. The relative risk of pregnancy for women treated with 10 mg mifepristone compared with those treated with 25 mg was 1.0 (95% CI: 0.51–1.95) and equivalence was demonstrated within a two-fold margin. Both doses prevented 85–86% of pregnancies expected to have occurred if no treatment had been given. The pregnancy rate nearly doubled if women had further acts of intercourse. Efficacy decreased with treatment delay. Side-effects were uncommon and mild. CONCLUSIONS: A dose of 10 mg of mifepristone is sufficient for emergency contraception. Earlier treatment is preferable, although the method can be used effectively for up to 5 days after intercourse.
Key words: dose/efficacy/emergency contraception/mifepristone/RCT
* *On behalf of the Clinical Research Team of Collaborative Research and Development on Mifepristone to reduce unwanted pregnancies and recourse to Abortion.
4 To whom correspondence should be addressed. E-mail: xiaobl{at}public.bta.net.cn
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