(Updated January 2008)

The term “emergency contraception” (also known as “the morning-after pill” or “postcoital contraception”) refers to contraceptive methods that can be used to prevent pregnancy after sex. Methods currently available include 1) a ‘dedicated’ product (approved specifically for emergency contraception) called Plan B^® that contains synthetic progesterone, 2) high doses of commonly available birth control pills that contain synthetic estrogen and progesterone, and 3) insertion of a Copper T intrauterine device, commonly called an IUD.

Emergency contraception offers an important chance to prevent an unintended pregnancy when a regular method fails, no method was used, or sex was forced. Research has shown that emergency contraception is extremely safe and effective and can reduce the chance that pregnancy will happen after a single act of intercourse by between 75 and 99 percent.

Emergency Contraceptive Pills

Emergency contraceptive pills (ECPs) are used to prevent pregnancy after unprotected sex (sex without effective birth control). The sooner after unprotected sex ECPs are used, the more effective they are.^1,2

Several brands of dedicated emergency contraceptive pills—products that are specially packaged and labeled for this indication—are available throughout the world. Only one brand, Plan B, is available in the United States. Certain daily oral contraceptive pills that contain a combination of estrogen and progesterone also can be used as ECPs when prescribed in higher-than-normal doses. The regimens that contain both hormones do not work as well as Plan B. There are no known medical conditions that preclude the use of ECPs. ECPs are not indicated in women with confirmed pregnancy because they will have no effect.

Mode of Action

The exact mode of action of ECPs in any given case cannot be known, because it probably depends on the time in a woman’s menstrual cycle when intercourse occurred and when ECPs were taken.^3,4 ECPs have been shown to inhibit or delay an egg from being released from the ovary when taken before ovulation. They also may prevent sperm and egg from uniting or stop a fertilized egg from attaching to the uterus. ECPs do not interfere with an established pregnancy.

Side Effects

Side effects include nausea and vomiting, delay in menses, irregular vaginal bleeding, abdominal pain, breast tenderness, headache, dizziness, and fatigue. These side effects usually do not occur more than a few days after treatment, and they generally resolve within 24 hours.⁵ Women who use Plan B have much lower rates of side effects than women who use regimens that contain both estrogen and progesterone.

In countries where ECPs are not available over the counter, ARHP encourages health care providers to offer their patients advance prescriptions for ECPs during routine checkups or over the phone.

Availability of ECPs

Research has shown ECPs to be appropriate for over-the-counter use, and they are easily available without a prescription in many countries. ECPs treat a condition that patients can diagnose themselves; they are safe and effective when used without direct prescriber supervision; and the drug’s label adequately explains potential adverse effects and conditions of use. ECPs are simple to use, are not addictive, and have no known health hazards when self-administered. There are virtually no contraindications, and side effects are minor and temporary. In sum, there is no compelling medical rationale for restricting ECPs to prescription-only use.

In the United States, ECPs are available at pharmacies without a prescription to women and men 18 and older. Younger women may obtain ECPs from a pharmacy or clinic with a prescription. In some states, pharmacists have collaborative practice agreements in place that enable them to prescribe ECPs directly to younger women.

ECP Regimens

Copper T IUD Insertion

Copper-containing IUDs are an effective and safe method of emergency contraception. One study documented a high effectiveness with this form of emergency contraception, with an estimated failure rate of less than 0.1%.⁶ The devices can be inserted up to the time of implantation, which is about five to seven days after ovulation. However, most providers limit insertion to within five days of intercourse rather than ovulation, because it is often difficult to estimate the day of ovulation. The hormone-releasing intrauterine system (LNG IUS) should not be used as emergency contraception.

Mode of Action

When the copper-containing IUD is used as emergency contraception, its most likely mechanism of action is interference with implantation from the effect of the copper ions or the presence of the IUD itself.⁷

Side Effects

Side effects seen after postcoital insertion of an IUD are similar to those seen after insertion at other times, and include heavy bleeding or cramping.

References

1. Piaggio G, von Hertzen H, Grimes D, et al. Timing of emergency contraception with levonorgestrel or the Yuzpe regimen. Task Force on Postovulatory Methods of Fertility Regulation. Lancet 1999;353:721.
2. Task Force on Postovulatory Methods of Fertility Regulation. Randomised controlled trial of levonorgestrel versus the Yuzpe regimen of combined oral contraceptives for emergency contraception. Lancet 1998;352:428-433.
3. Grimes DA, Raymond EG. Emergency contraception. Ann Intern Med 2002;137:180-189.
4. Croxatto HB, Devoto L, Durand M, et al. Mechanism of action of hormonal preparations used for emergency contraception: a review of the literature. Contraception 2001;63:111-121.
5. Van Santen MR, Haspels AA. Interception II: postcoital low-dose estrogens and norgestrel combination in 633 women. Contraception 1985;31:275-293.
6. Trussell J, Ellertson C. Efficacy of emergency contraception. Fertility Control Reviews 1995;4:8-11.
7. Van Look PFA, Stewart F. Emergency contraception. In: Hatcher RA, Trussell J, Stewart F, et al, eds. Contraceptive Technology. 17th ed. New York: Ardent Media;1998.