目的　以左炔诺孕酮为参比制剂 ,观察 2 5mg米非司酮用于紧急避孕的临床效果、副反应及可接受性。方法　采用开放性随机对照性试验方法 ,按研究方案接纳单次无保护性交 72小时内要求紧急避孕的妇女 2 0 0例 ,随机分配到观察组 (n =10 0 )和对照组 (n =10 0 )。观察组单次口服 2 5mg米非司酮 (1片 ) ;对照组口服左炔诺孕酮 (毓婷 ) 0 75mg(1片 ) ,12小时后再服左炔诺孕酮 0 75mg(1片 )。服药后嘱两组对象按期随访直至月经来潮 ,并观察其避孕效果 ,副反应 ,对月经的影响及药物可接受情况。结果　采用经典Dixon方法计算 ,两组对象各有 1例妊娠 ,观察组避孕效果达 88 2 9% ,对照组为 89 13 % ,统计学上无明显差异 ;两组副反应轻 ,无任何不良反应发生。结论　小剂量米非司酮用于紧急避孕的效果与左炔诺孕酮是等效的 Objective To levonorgestrel as a reference preparation, observation of 25mg mifepristone for emergency contraception clinical effects, side effects and acceptability. Methods The open-label randomized controlled trial was used to receive 200 cases of emergency contraception within 72 hours of unprotected sexual intercourse according to the research plan and randomly assigned to observation group (n = 10 0) and control group (n = 10 0). The observation group received oral administration of 25 mg of mifepristone (1 tablet). In the control group, levonorgestrel 0 75 mg (1 tablet) was orally administered. Twelve hours later levonorgestrel 0 75 mg (1 tablet) . After taking the medication, both groups were given regular follow-up until menstrual cramps, and observe their contraceptive effects, side effects, menstrual effects and drug acceptance. The results were calculated by the classic Dixon method. One case of pregnancy was observed in each group, the contraceptive effect was 88.29% in the observation group and 89.13% in the control group, with no statistical difference. The two groups had mild side effects and no adverse reactions occur. Conclusions The effect of low dose mifepristone for emergency contraception is equivalent to that of levonorgestrel