Introduction
Emergency contraception (EC) has also been referred to as postcoital contraception or the “morning-after” contraception. Emergency contraception is the initiation of a reversible family planning method after coitus has taken place. Some couples, for a variety of reasons, are unable to anticipate the need for adequate contraception until after coitus has occurred. This may be the result of the failure of a contraceptive method (a condom breaks), the misuse or mistiming of a method, sexual assault or both partners neglect to practice contraception. Pregnancy may result from a single sexual encounter if the coital experience was either unprotected or inadequately protected. The risk of pregnancy from one coital exposure at any time during the menstrual cycle, irrespective of the regularity of the woman’s cycles and at any age in the reproductive years, has been estimated at 3%. The risk of pregnancy from one coital exposure at mid-cycle has been estimated to be 9% [1]. Thus, there is a need for reversible pregnancy prevention that can be administered after coitus has occurred.
Combination oral contraceptives
The first documentation in the literature of high-dose estrogens used as EC was in a victim of sexual assault in the 1960s. In 1974, a combined estrogen and progestin regimen was later termed the “Yuzpe” method, after the Canadian physician who described it. And a dedicated product, Preven, was introduced in 1998. However, the World Health Organization published a world-wide multicenter randomized control trial showing that progestin-only EC was more effective than the Yuzpe method (85% versus 57% of pregnancies prevented), with fewer side effects [2]. The rates of nausea and vomiting were 50% versus 23% and 19% versus 6% respectively for Yuzpe and progestin-only, respectively. While still considered a safe method, Preven was withdrawn from the market and the use of combined oral contraceptives is now considered an acceptable method of EC only if progestin-only methods are unavailable. An emergency contraceptive regimen of combined oral contraceptive pills taken initially within 72 hours of unprotected or inadequately protected intercourse which provides a total of 500–600 μg of levonorgestrel and 100–120 μg of ethinylestradiol in each of two doses taken 12 hours apart. It should be administered with an antiemetic, such as meclizine, if possible.
Plan B, consisting of two tablets each containing 750 μg of levonorgestrel, was approved by the FDA in 1999 to be taken as one pill every 12 hours up to 72 hours after unprotected coitus. The efficacy of the regimen is inversely related to the interval between unprotected coitus and the initiation of emergency contraception, but has been shown to be effective up to 120 hours after unprotected intercourse [3]. The sooner this regimen of EC is started after a single act of unprotected sex, the more effective it is. Additionally, both tablets of levonorgestrel can be administered simultaneously with no difference in the side effect profile [4]. This is preferable to the one tablet every 12 hours regimen, because if the second dose is missed, efficacy is decreased.
The risk of pregnancy following a single act of unprotected sex is dependent not only on how soon after coitus the dose is taken, but also on the probability of clinical pregnancy resulting from the single act of intercourse. The overall proportion of pregnancies prevented in the 1998 WHO trial was 85% [2]. A combination of progestin-only pills equivalent to 1.5 mg of levonorgestrel may be used and a generic version Next Choice is currently available. Levonorgestrel EC can safely be used in women of all ages, and is currently available in the United States to women 17 years and older without a prescription. The pharmacokinetics of EC are the same in women <18 years as in adults; they can also correctly and safely self-administer EC without medical supervision, and do not demonstrate an increase in sexual risk taking when provided access to EC [5].
The American College of Obstetricians and Gynecologists recommends offering EC to victims of sexual assault. While effective in preventing pregnancy, levongestrel EC provides no protection against sexually transmitted infections, and so prophylaxis against sexually transmitted infections should be offered [6]. The ACOG also recommends discussing EC in advance of need along with routine methods of birth control at the periodic assessment of patients for every age range starting at age 13, except those 65 and older [7]. Patients must understand the indications for EC use relative to their chosen contraceptive method (Box 113.1) [8]. Providing a prescription for EC in advance of need is not associated with abandonment of user-dependent contraceptive methods and does not increase risk of sexually transmitted infections
While women with advanced provision take EC sooner and more often, some women who theoretically have increased access to EC still fail to use EC with every act of unprotected intercourse and thus advance provision of EC has failed to reduce rates of unintended pregnancy over routinely offering information about EC [9]. EC is not readily available in all pharmacies and advanced provision allows patients to access to Plan B in a more timely fashion.
Box 113.1 Indications for use of emergency contraception
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