Update on emergency contraception.

Emergency contraception is a woman's last chance to prevent unintended pregnancy. Ulipristal acetate, a selective progesterone receptor modulator, when taken as a single 30 mg dose, is a new, safe and effective emergency contraceptive that can be used from the first day and up to 5 days following unprotected intercourse. The older progesterone-only emergency contraceptive, levonorgestrel, is taken as two 0.75 mg pills 12 hours apart (Next Choice(®); Watson Pharmaceuticals Inc., Morristown, NJ, USA) or a single 1.5 mg pill (Plan B One-Step™; Watson Pharmaceuticals Inc.), and is approved for only 72 hours after unprotected intercourse. During clinical development, ulipristal acetate has been shown to be more effective than levonorgestrel in delaying or inhibiting ovulation. A recent meta-analysis of two randomized clinical trials showed ulipristal acetate to have a pregnancy risk 42% lower than levonorgestrel up to 72 hours and 65% lower in the first 24 hours following unprotected intercourse. Moreover, when taken beyond 72 hours, significantly more pregnancies were prevented with ulipristal acetate than with levonorgestrel. Side effects are mild and similar to those seen with levonorgestrel. Ulipristal acetate was approved for emergency contraception by the US Food and Drug Administration in August 2010, and has been launched in the USA as ella(®) (Watson Pharmaceuticals Inc.) since December 1, 2010. Ella is prescription only and is priced comparable to Plan B One-Step.