Progestin-only emergency contraceptives commonly available include a two-dose regimen and a single-dose regimen.  In the two-dose regimen, a pill containing 0.75 mg of levonorgestrel is taken followed by a second 0.75 levonorgestrel pill 12 hour later.  In the single-dose regimen, a single tablet containing 1.5 mg of levonorgestrel is taken.  Both regimens are available over-the-counter and without a prescription for women 17 years and older but a prescription is required for women younger than 17 years.   In both regimens, the medication should be taken as soon as possible but no later than 120 hours after unprotected intercourse.  The medications work better the sooner you take them, but in general are 98% effective.

Non-hormonal Emergency Contraception

The second class of emergency contraceptives are non-hormonal contraceptives.  These include the copper intrauterine device (IUD) and ulipristal acetate, a medication that blocks the action of progestin.

The Copper intrauterine device is a T-shaped piece of plastic-like material with a copper band along the stem, about the size of a standard paper clip. Your doctor places it into the uterus through the vagina.  Unlike hormonal methods of emergency contraception, the IUD is effective up to 5 days after unprotected intercourse.  It also has the advantage of being extremely effective (>99.8% efficacy) and lasts up to 10 years (though it can be removed at any time).  The IUD works by preventing fertilization.

Ulipristal acetate is a medication that binds to the progesterone receptor and therefore prevents naturally produced progesterone from functioning to support pregnancy. It is effective up to 120 hours after unprotected intercourse. Ulipristal acetate is as effective as Levonorgestrel.