Prescrire Int. 2010 Apr;19(106):53-5.
Postcoital contraception, also known as emergency contraception, is currently based on a single 1.5 mg dose of levonorgestrel, a progestin, taken within 3 days after unprotected intercourse. However, efficacy appears to be similar when the drug is taken within 4 or 5 days. Ulipristal, a progesterone receptor agonist-antagonist, is now authorised in the European Union for postcoital contraception within 5 days after unprotected intercourse. Clinical evaluation of ulipristal in this setting is based on two trials versus levonorgestreland one non-comparative trial. One double-blind trial in 1672 women failed to show that ulipristal, taken within 3 days following intercourse, was any more effective than levonorgestrel. In another trial including 1893 women, ulipristal was not statistically more effective than levonorgestrel when the two drugs were taken within 5 days after intercourse. In a non-comparative trial in 1533 women who took ulipristalon the third, fourth or fifth day after intercourse, the pregnancy rate was 2.1%. This is lower than would be expected without contraception (about 5.5%) but an indirect comparison, providing only a low level of evidence, did not show superiority over levonorgestrel. Ulipristal, like levonorgestrel, can cause nausea and vomiting, and menstrual disorders. A few cases of ovarian cysts were observed with ulipristal, two of which required surgery. Co-administration of enzyme inducers may reduce the efficacy of both ulipristal and levonorgestrel. Little information is available on the risks incurred by the mother or child when ulipristal fails to terminate a pregnancy. As ulipristal has no proven advantages, postcoital contraception should continue to be based on levonorgestrel, a better-assessed drug. Levonorgestrel can be used up to 5 days after unprotected intercourse, even though it is only approved for use during the first 3 days.
性交后避孕，也称为紧急避孕，目前是在无保护性交后3天内单次服用1.5毫克左炔诺孕酮（一种孕激素）。然而，在4天或5天内服用该药物时，疗效似乎相似。乌利司他是一种孕激素受体激动剂 - 拮抗剂，目前在欧盟已获批准用于无保护性交后5天内的性交后避孕。乌利司他在此情况下的临床评估基于两项与左炔诺孕酮对比的试验和一项非对比试验。一项针对1672名女性的双盲试验未能表明性交后3天内服用的乌利司他比左炔诺孕酮更有效。在另一项纳入1893名女性的试验中，当两种药物在性交后5天内服用时，乌利司他在统计学上并不比左炔诺孕酮更有效。在一项针对1533名在性交后第三天、第四天或第五天服用乌利司他的女性的非对比试验中，妊娠率为2.1%。这低于未采取避孕措施时预期的妊娠率（约5.5%），但作为仅提供低水平证据的间接比较，并未显示出其优于左炔诺孕酮。与左炔诺孕酮一样，乌利司他会引起恶心、呕吐和月经紊乱。观察到少数使用乌利司他导致卵巢囊肿的病例，其中两例需要手术治疗。酶诱导剂的共同给药可能会降低乌利司他和左炔诺孕酮的疗效。当乌利司他未能终止妊娠时，关于母亲或孩子所面临风险的信息很少。由于乌利司他没有已证实的优势，性交后避孕仍应以左炔诺孕酮为基础，左炔诺孕酮是一种评估更充分的药物。左炔诺孕酮可在无保护性交后5天内使用，尽管它仅被批准在前3天使用。
