Ulipristal Acetate: Review of the Efficacy and Safety of a Newly Approved Agent for Emergency Contraception

Abstract 

Background

Emergency contraception (EC) is used to prevent unintended pregnancies. The current gold standard for oral EC is levonorgestrel (LNG) administered as a single 1.5-mg dose or in 2 doses of 0.75 mg separated by 12 hours. LNG has shown to be effective up to 72 hours after coitus. Ulipristal acetate (UPA) is a selective progesterone receptor modulator approved for EC use in the United States in August 2010. UPA is administered as a one-time, 30-mg dose within 120 hours of intercourse.

Objective

The goal of this review was to provide a summary of the available literature on the use of UPA for EC.

Methods

PubMed, Cochrane Library, ClinicalTrials.gov, International Pharmaceutical Abstracts, EBSCO, and Iowa Drug Information Service were searched from February 2011 through September 2011 to identify relevant articles. Search terms included ulipristal acetate, CDB-2914, VA 2914, and emergency contraception.

Results

In an open-label study, UPA was effective in preventing pregnancy in 1241 women who presented for EC up to 120 hours (5 days) after unprotected intercourse, with an observed pregnancy rate of 2.1% (95% CI, 1.4%–3.1%) versus 5.5% (ie, the expected pregnancy rate without EC). The efficacy of UPA did not decrease significantly (P = 0.44) over time, with pregnancy rates at intervals between >48 and 72 hours at 2.3% (95% CI, 1.4%–3.8%), >72 and 96 hours at 2.1% (95% CI, 1.0%–4.1%), and >96 and 120 hours at 1.3% (95% CI, 0.1%–4.8%). In a single-blind, comparative noninferiority study of 1696 women, UPA was at least as effective as LNG when used within 72 hours for EC, with 15 pregnancies in the UPA group and 22 pregnancies in the LNG group (odds ratio = 0.68 [95% CI, 0.35–1.31]). In addition, UPA prevented significantly (P = 0.037) more pregnancies than LNG when used between 72 and 120 hours after unprotected intercourse, with 0 pregnancies in the UPA group and 3 pregnancies in the LNG group. In a meta-analysis, UPA prevented a greater percentage of pregnancies than LNG at intervals up to 24 hours (0.9% UPA vs 2.5% LNG; P = 0.035), up to 72 hours (1.4% UPA vs 2.2% LNG; P = 0.046), and up to 120 hours (1.3% UPA vs 2.2% LNG; P = 0.025). The most commonly (>10%) reported adverse events included headache, nausea, and abdominal pain. In addition, UPA delayed onset of menstruation by a mean of 2.1 to 2.8 days.

Conclusions

Based on clinical trials, UPA seems to be a reasonably tolerable and effective method of EC when used within 120 hours of intercourse. UPA is at least as effective as LNG when used within the first 72 hours after unprotected intercourse. However, UPA may be more effective than LNG when used between 72 to 120 hours after unprotected intercourse, extending the window of opportunity for EC. UPA may provide a new option for women who require EC up to 5 days after unprotected intercourse.

Key words:  CDB-2914 , emergency contraception , selective progesterone receptor modulator , ulipristal acetate , VA 2914