Drug therapy - Emergency postcoital contraception

In the US, few products are marketed for emergency contraception and drug manufacturers have been reluctant to enter this market, despite invitations from the US Food and Drug Administration to do so. When started within 72 hours after unprotected intercourse, a combination of ethinyl estradiol and levonorgestrel is at least 75% effective against pregnancy. The antiprogestin mifepristone is even more effective and has fewer side effects. Other emergency methods include progestin alone, the antigonadotropin danazol, and postcoital insertion of an IUD. This article reviews the modes of action of emergency contraception (effects on ovulation, fertilization, gamete transport, the corpus luteum, and implantation), its indications, and the efficacy of the various regimens. The lack of availability and promotion of emergency contraception in the US is, in large part, a result of opposition from anti-abortion groups. Since this method acts before implantation, it cannot be considered an abortifacient.