[Effects of mifepristone of different doses on emergency contraception, a randomized double-blind study].
OBJECTIVE
To compare the effects of mifepristone of different doses on emergency contraception.


METHODS
3,052 healthy women with regular menstrual cycle who visited the 10 family planning institutes and hospitals in Beijing, Shanghai, Shangdong, Sichuan, Tianjin, Guangdong, and Liaoning for emergency contraception within the period of 120 hours after a single act of unprotected sex were given a single dose of 10 mg or 25 mg mifepristone randomly and double-blindly. They were asked to record the vaginal hemorrhage that would occur and not to have unprotected sex until the next menstrual onset when they were followed up. The trial for a specific subject ended when she menstruated. If the menstruation was irregular or a specific subject failed to menstruate on time a blood or urine human chorionic gonadotropin (hCG) test was made. If the hCG test was negative, an appointment was made to follow up once one week later. If the hCG test was positive ultrasound examination was made to detect pregnancy. If the subject still failed to menstruate and the hCG test was still negative follow-up for this subject could be finished.


RESULTS
Twenty-two of the 3,052 subjects were lost to follow up. Among the remaining 3,030 women 1,516 were in the 10 mg group and 1 514 in the 25 mg group. Seventeen pregnancies occurred in each group, with a pregnancy rate of 1.1% for both groups. The relative risk of pregnancy of treatment of 25 mg mifepristone in comparison with treatment of 10 mg mifepristone was 1.0 (95% CI: 0.51-1.95). Both doses prevented about 85% approximately 86% of the anticipated pregnancy if no measure had been adopted. The pregnancy rate nearly doubled in the women who had unprotected sex after treatment of mifepristone. The efficacy of mifepristone decreased along with the delay of mifepristone administration. Side effects were uncommon and mild. Delay of 7 days or more in the onset of next menstruation occurred in 9%-10% of the women.


CONCLUSIONS
Mifepristone of the dose of 10 mg is safe and effective for emergency contraception. Earlier administration is preferable, although the method can be used effectively up to five days after the unprotected sex.
Xiao
Bi-lian
BL
National Research Institute for Family Planning, Beijing 100081, China. xiaobl@public.bta.net.cn
von Hertzen
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Zhao
Heng
H
Piaggio
Gilda
G
Wu
Shang-chun
SC
Huang
Jun
J
Weng
Li-ju
LJ
Zhang
Li-jia
LJ
Cheng
Li-nan
LN
Ren
Fang-ming
FM
He
Chang-hai
CH
Gui
You-lun
YL
Huang
Zhen-jia
ZJ
Lei
Zhen-wu
ZW
Zhu
Ming-hui
MH
Song
Li-juan
LJ
Cao
Xiao-ming
XM
Wang
Rong-fen
RF
Ding
Wan-hua
WH
Mei
Qing-ming
QM
Ni
Feng-xian
FX
Zheng
Ning
N
D000328:Adult; D003267:Contraception / Q000379:methods*; D003283:Contraceptives, Postcoital, Synthetic / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004630:Emergencies; D005260:Female; D006801:Humans; D015735:Mifepristone / Q000008:administration & dosage*; D011247:Pregnancy
D003283:Contraceptives, Postcoital, Synthetic; D015735:Mifepristone