Ulipristal acetate (ellaOne) was licensed in May 2009 for emergency contraception within 120 hours (5 days) of unprotected intercourse or contraceptive failure. 

One 30mg dose should be taken as soon as possible, but no later than 120 hours after, unprotected intercourse.  The dose can be taken with or without food, and should be repeated if vomiting occurs within 3 hours of taking it.

Reduced plasma concentrations of ulipristal can occur if taken with CYP3A4 inducers and drugs that increase plasma pH.  Potent CYP3A4 inhibitors can increase exposure to ulipristal. Women who are using a hormonal contraceptive that contains progesterone and who have taken ulipristal should use a reliable barrier method until the next menstrual period starts, because ulipristal can interfere with progesterone-containing products.

In a phase II study, the efficacy of ulipristal (n=775) was compared to that of levonorgestrel (n=774) when taken up to 72 hours after unprotected intercourse.  The observed number of pregnancies occurring with ulipristal treatment was lower than that with levonorgestrel treatment.  The difference in pregnancy rates was -0.8% in favour of ulipristal.  Non-inferiority of ulipristal to levonorgestrel was shown.

In a larger phase III study the efficacy of ulipristal when taken between 48 to 120 hours after unprotected intercourse was assessed.  No active control was used. The observed pregnancy rate of 2.1% was lower than the calculated pregnancy rate of 5.53%.  

There is a Phase III study comparing the efficacy of ulipristal with levonorgestrel when taken up to 120 hours after unprotected intercourse in 1899 women. [This use is outside of the levonorgestrel product licence].  The observed pregnancy rate after taking emergency contraception up to 72 hours after unprotected intercourse in the ulipristal group (n=15, 1.8%) was statistically significantly lower than that seen in the levonorgestrel group (n=22, 2.6%). The number of pregnancies in women taking emergency contraception between 72-120 hours after unprotected intercourse was 0 in 97 women in the ulipristal group and 3 in 106 women in the levonorgestrel group.

There is limited information on the effects of ulipristal on pregnancies which have resulted in live births.