The use of a method after intercourse to prevent pregnancy is commonly called postcoital contraception, or the “morning after” treatment. “Emergency contraception” is a more accurate and appropriate name, indicating the intention to be one-time protection. It is an important option for patients, and should be considered when condoms break, sexual assault occurs, if diaphragms or cervical caps dislodge, or with the lapsed use of any method. In studies at abortion units, 50% to 60% of the patients would have been suitable for emergency contraception and would have used it if readily available.¹,² In the United States, it is estimated that emergency contraception could annually prevent 1.7 million unintended pregnancies, and the number of induced abortions would decrease by about 40%.³ Nevertheless, increasing access to emergency contraception has not had an impact on pregnancy or abortion rates in clinical trials, apparently because the actual use is insufficient to have an impact on the general population.⁴,⁵,⁶ Availability must be accompanied by education and motivation. Clinicians should be aware that younger adolescents can safely use emergency contraception.⁷

Many women do not know of emergency contraception, and it has been difficult to obtain.²,⁸ Even if women are aware of this method, accurate and detailed knowledge is lacking.⁹ A favorable attitude toward this method requires both knowledge and availability. Availability should be favorably influenced in the United States by the recent Food and Drug Administration approval making levonorgestrel emergency contraception available without a prescription to women older than age 16.

Women who have used emergency contraception are very satisfied with the method, and most importantly, do not express an intention to substitute this method for regular contraception.¹⁰ The use of emergency contraception
by adolescents is not associated with an increase in sexually transmitted infections (STIs).¹¹

Information for patients and clinicians, including the latest available products, can be obtained from the website and hotline maintained by the Office of Population Research at Princeton University:

http://ec.princeton.edu.

Telephone hotline: 1-888-NOT-2-LATE (1-888-668-2528)

The use of large doses of estrogen to provide emergency contraception was pioneered by Morris and van Wagenen at Yale in the 1960s. The initial work in monkeys led to the use of high doses of diethylstilbestrol (25 to 50 mg/d) and ethinyl estradiol in women.¹² It was quickly appreciated that these extremely large doses of estrogen were associated with a high rate of gastrointestinal side effects. Yuzpe developed a method utilizing a combination oral contraceptive, resulting in an important reduction in dosage.¹³ The following treatment regimens, or their generic equivalents, have been documented to be effective:

In the United States, Plan B containing only levonorgestrel (two 0.75-mg tablets) was approved by the Food and Drug Administration for nonprescription sales to women aged 17 and older, and by prescription for those younger, one tablet taken within 120 hours of intercourse and the second 12 hours later. The two tablets can be combined into a single, onetime dose of 1.5 mg levonorgestrel with no loss of efficacy or increase in side effects.¹⁶,¹⁷ The single-dose product, Plan B one-step, is approved and available in the United States also without a prescription for women 17 and older. The two-dose product is now available in the United States in a generic version known as Next Choice.

In some countries, a kit (Preven) is also available containing four tablets, each containing 50 µg ethinyl estradiol and 0.250 mg levonorgestrel, to be used in the usual fashion, two tablets followed by two tablets 12 hours later.

Clinicians should consider providing advance information and a prescription or an emergency contraceptive kit to patients (a kit can be a simple envelope containing instructions and the appropriate number of oral contraceptives) to be taken when needed. It would be a major contribution
to our efforts to avoid unwanted pregnancies for all patients without contraindications to oral contraceptives to have emergency contraception available for use when needed. In our view, this would be much more effective in reducing the need for abortion than waiting for patients to call. In studies of self-administration, adult women in Scotland and younger women in California increased the use of emergency contraception without adverse effects such as increasing unprotected sex.¹⁸,¹⁹,²⁰ Women are able to use this nonprescription access effectively and do not develop a reliance on emergency contraception as a regular method.²¹

There is strong evidence that treatment with emergency contraception acts primarily by preventing or delaying ovulation and by preventing fertilization.²²,²³,²⁴,²⁵,²⁶ Studies have indicated that emergency contraception does not prevent implantation.²⁷,²⁸,²⁹ Experiments in monkeys and rats could detect no effect of a high dose of levonorgestrel administrated postcoitally once fertilization had occurred.³⁰,³¹ The evidence indicates that a postfertilization effect does not contribute to the efficacy of emergency contraception.²⁵,³⁰,³¹,³²,³³ Clinicians, pharmacists, and patients can be reassured that treatment with emergency contraception is not an abortifacient.

Efficacy has been confirmed in large clinical trials and summarized in complete reviews of the literature.¹⁵,³⁴,³⁵,³⁶ Treatment with high doses of estrogen or with levonorgestrel yields a failure rate of approximately 1%, with the combination oral contraceptive, about 2% to 3%. The failure rate is lowest with high doses of ethinyl estradiol given within 72 hours (0.1%), but the side effects make this a poor choice. In general clinical use, the method with oral contraceptives can reduce the risk of pregnancy by about 75%; this degree of reduction in probability of conception (given the relatively low chance, about 8%, for pregnancy associated with one act of coitus)³⁷ yields the 2% failure rate measured in clinical studies.³⁸,³⁹,⁴⁰

Treatment should be initiated as soon after exposure as possible, and the standard recommendation is that it be no later than 120 hours. Careful assessment of the reported experience with emergency contraception indicated that the method is equally effective when started on the first, second, or third day after intercourse (which would allow user-friendly scheduling), and that efficacy extends beyond 72 hours.⁴¹,⁴² Data from the World Health Organization randomized, clinical trial, however, support the importance of timing, finding a reduction in efficacy after 72 hours, and the greatest protection occurring when the medication is taken within 24 hours
of intercourse.⁴³ Postponing the dose by 12 hours raises the chance of pregnancy by almost 50%. For this reason, the treatment should be initiated as soon as possible after sexual exposure, an important argument in favor of advance provision.

We should emphasize, in case the patient is already pregnant, that there is no evidence that exposure to the amounts of estrogen and progestin in oral contraceptives is an abortifacient or teratogenic.⁴⁴,⁴⁵,⁴⁶ Thus, emergency contraception is ineffective in the presence of an established pregnancy. A delay in menses after treatment warrants testing for pregnancy and consideration for the possibility of an ectopic pregnancy.

When using oral contraceptives for emergency contraception, it is worth adding an antiemetic, oral or suppository, to the treatment; a long-acting nonprescription agent, 25 or 50 mg meclizine (Bonine, Dramamine II, Antivert) is recommended, to be taken 1 hour before the emergency contraception treatment. Side effects reflect the high doses used: nausea and vomiting, 50% and 20% with estrogen-progestin oral contraceptives, but only 18% and 4% with levonorgestrel.¹⁵,¹⁶,¹⁷ Other reactions include breast tenderness, headache, dizziness, and bleeding or spotting in the month after treatment. If a patient vomits within an hour after taking pills, additional pills must be administered as soon as possible. Nausea and vomiting are experienced at such a lower rate with the levonorgestrel-only method that an antiemetic is not necessary.

An analysis of the U.K. General Practice Research Database could find no evidence for an increased risk of venous thromboembolism with the short-term use of oral contraceptives for emergency contraception (indeed, no cases were found for as long as 60 days after use in more than 100,000 episodes of use).⁴⁷ Although short-term treatment with combined oral contraceptives has been documented to have no effect on clotting factors, in our view the usual contraindications for oral contraception apply to this use.⁴⁸ Because of the high dose of estrogen, emergency contraception with combined oral contraceptives should not be provided to women with either a personal or a close family history (parent or sibling) of idiopathic thrombotic disease. For women with a contraindication to exogenous estrogen, the progestin-only method with levonorgestrel should be used for emergency contraception. The levonorgestrel-only method is the treatment of choice anyway because of greater efficacy and fewer side effects.