Progestin-only Emergency Contraceptive Pills ("Morning After Pills")
Progestin-only emergency contraceptive pills ("morning after pills") are pills that contain levonorgestrel, a type of the hormone progestin researchers have found prevents pregnancy when taken in the few days after sex. In the United States, the only progestin-only emergency contraceptive pill is Plan B.
The package for Plan B has two emergency contraceptive pills (each containing 0.75mg of levonorgestrel), and the instructions tell you to take them 12 hours apart. Recent studies show that you can take both pills (the full 1.5mg dose) at the same time, and one-pill emergency contraceptives are already available in a number of other countries. Research also shows that you can use emergency contraception up to 120 hours after sex, even though the instructions say to take the pills within 72 hours. About one woman in four (23%) feels sick to her stomach and about one in 17 (6%) throws up after taking progestin-only emergency contraception. (For more details about using these pills, click here.)
Plan B and other progestin-only emergency contraceptive pills reduce your risk of pregnancy by about 89%. Don't worry, that doesn't mean 11 percent of women get pregnant using these morning after pills. It just means that this type of emergency contraception prevents 89% of the pregnancies researchers would expect would happen when a woman doesn't use birth control, her contraception fails (like the condom breaks or falls off), or she is forced to have sex. Usually, if 100 women have sex without using birth control one time during the second or third week of their menstrual cycle, about 8 of them will get pregnant. But if those same 100 women also use progestin-only emergency contraceptive pills, only one will get pregnant. And emergency contraception works better the sooner you take it after sex.
To learn which brands of emergency contraception and daily birth control pills can be found in the United States or any other country, try using our up-to-date database. In addition to progestin-only emergency contraception, you can also use certain brands of birth control pills that contain two hormones (both progestin and estrogen) or the Copper-T IUD to prevent pregnancy after sex.
In the United States, Plan B was approved by the FDA for sale without
a prescription to women and men 18 years and older on August 24, 2006,
and by mid-November the nonprescription package has been shipped out to most pharmacies. Women aged 17 and younger will still
require a prescription to buy Plan B. Click
here for more information on how that age restriction will be
enforced and whether other people — parents, siblings, or friends
— who are 18 and older will be able to buy Plan B and then give
it to minors.
For a more detailed academic review of the medical and social science
literature about emergency contraception, click
here 
.