Emergency contraception.

Research on the postcoital use of contraceptive steroids began in the 1960s. The first oral regimen, which used a widely available brand of combined estrogen–progestin oral contraceptive pills, was published in 1974 (7). Research on progestin-only regimens for occasional postcoital use by women having infrequent sexual intercourse also began at approximately the same time (8). Data regarding the use of IUDs as emergency contraceptives were initially published in the 1970s and, more recently, selective progesterone receptor modulators were introduced. The most commonly used oral emergency contraceptive regimen is the progestin-only pill, which consists of 1.5 mg of levonorgestrel (Table 1). This product can be purchased over the counter and is available without age restriction as of 2013. The product using two levonorgestrel doses of 0.75 mg has fallen out of use in favor of the simpler one-dose regimen, which is at least as effective as the two-dose product (9, 10). The levonorgestrel regimen is labeled for use for up to 72 hours after unprotected sex but is best used as soon as possible after unprotected sex (10–14) (Table 1). A second dedicated emergency contraceptive, a pill containing 30 mg of ulipristal acetate, was approved by the FDA in 2010 and requires a prescription. This selective progesterone receptor modulator, or antiprogestin, has demonstrated effectiveness up to 120 hours after unprotected sex (14) (Table 1). Combined estrogen–progestin emergency contraceptive regimens are no longer sold as a dedicated product. Emergency Contraception