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- McKeage, K. & Croxtall, J.D. Drugs (2011) 71: 935. doi:10.2165/11207410-000000000-00000
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Ulipristal acetate (ellaOne®; ella®) is the first of a new class of selective progesterone receptor modulators, and is indicated for emergency contraception within 120 hours after unprotected sexual intercourse or contraceptive failure. The principal effect of ulipristal acetate is to inhibit or delay ovulation. This effect may result from the drug's ability to delay the onset of luteinizing hormone (LH) surge or postpone LH peak if LH surge has started, or possibly by a direct inhibitory effect on follicular rupture, when administered in the follicular phase (including just before ovulation).
In clinical trials, a single oral dose of ulipristal acetate 30 mg was effective in preventing pregnancies in women requesting emergency contraception after unprotected sexual intercourse and provided sustained efficacy throughout the 120-hour postcoital period in which it is indicated. When compared with levo-norgestrel in well designed noninferiority trials, it was no less effective in preventing pregnancies when administered within 72 hours of unprotected intercourse, but was more effective when administered later (within 72–120 hours). Results of a meta-analysis suggest that ulipristal acetate may be more effective than levo-norgestrel from day 1 and throughout the entire 5-day period following unprotected sexual intercourse.
Ulipristal acetate is generally well tolerated, with a similar tolerability profile to that of levonorgestrel. In general, the onset of menses is delayed by 2–3 days following treatment. Although, ulipristal acetate is more expensive than levonorgestrel, it may represent a cost-effective alternative to levonorgestrel for women requesting emergency contraception within 120 hours of unprotected intercourse. Thus, ulipristal acetate provides effective, sustained and well tolerated emergency contraception when taken within 120 hours of unprotected sexualintercourse, thereby offering an extended treatment window compared with levonorgestrel, which should be administered within 72 hours.