Emergency contraception is used to prevent pregnancy after unprotected or inadequately protected sexual intercourse. Common indications include contraceptive failure (e.g., condom breakage, missed doses of oral contraceptives) and failure to use any form of contraception. Although the first emergency contraceptive was approved by the U.S. Food and Drug Administration more than a decade ago, many women are unaware of the existence of emergency contraception, misunderstand its use and safety, or do not use it when needed. Increasing awareness of emergency contraception is an important priority in the effort to prevent unintended pregnancies.

The universal availability of dedicated emergency contraception products has been controversial, and these drugs are currently separated into over-the-counter and prescription-only access based on patient age. There are two commonly used regimens: the combined estrogen/progestin regimen, which consists of two doses of 100 mcg of ethinyl estradiol plus 0.5 mg of levonorgestrel, taken 12 hours apart; and the progestin-only regimen, which consists of 1.5 mg of levonorgestrel, taken in one or two doses. The levonorgestrel-only regimen is more effective than the estrogen/progestin regimen and is associated with less nausea and vomiting. Therefore, it is the preferred method when available. A variety of standard oral contraceptives can be used for the combined regimen (see http://ec.princeton.edu/questions/dose.html#dose). When the estrogen/progestin regimen is used, an antiemetic agent may be taken one hour before the first dose to reduce the risk of nausea.

Patients using the two-dose progestin-only regimen are instructed to take 0.75 mg of levonorgestrel as soon as possible after intercourse, and another 0.75 mg 12 hours later. However, the regimen is equally effective if the second dose is taken up to 24 hours after the first; this dosing schedule may improve adherence. The single-dose levonorgestrel-only regimen is as effective as the two-dose regimen. Emergency contraception may be used more than once, even within the same menstrual cycle.

Treatment should be initiated as soon as possible after unprotected or inadequately protected sex. Effectiveness decreases with time, and it is not known if emergency contraception is effective when initiated more than 120 hours after intercourse. Therefore, emergency contraceptives should be made available to women who request it up to five days after intercourse. Emergency contraceptive regimens can be used by women with contraindications to conventional oral contraceptives.

Clinical examination and pregnancy testing are not necessary before prescribing emergency contraceptives. Clinical evaluation is indicated for women who have used emergency contraception if menses are delayed by a week or more, or if lower abdominal pain or persistent irregular bleeding develops. Some women have irregular bleeding or spotting in the week or month after using emergency contraception, but this resolves without treatment. The menstrual period usually occurs within one week before or after the expected time.

Information regarding effective long-term contraceptive methods should be made available whenever a woman requests emergency contraception. The copper intrauterine device is appropriate for use as emergency contraception for women who also desire long-acting contraception.