PHARMACOLOGY
Ulipristal is a selective progesterone receptor modulator.1 By preventing progesterone from occupying its receptor, ulipristal is thought to inhibit or delay ovulation and possibly also suppress maturation of the endometrium necessary for implantation of the embryo.2
As ulipristal interferes with the action of progesterone, it can reduce the efficacy of progesterone-containing contraceptives. Concomitant use with levonorgestrel for emergency contraception is not recommended.1
CLINICAL STUDIES
A pivotal study was undertaken to determine the efficacy of a single 30mg dose of ulipristal acetate in women aged 18 years or more who presented for emergency contraception 48-120 hours (2-5 days) after unprotected intercourse. In the primary efficacy analysis (n=1241), the rate of pregnancy was significantly lower than that which would have been expected in the absence of emergency contraception (2.1% versus 5.5%). The data indicated that ulipristal prevented 62% of expected pregnancies. The drug's efficacy was maintained over time: reported pregnancy rates were 2.3 per cent when used 48-72 hours (i.e. on day 3) after intercourse, 2.0% when used from 73-96 hours (i.e. on day 4) and 1.3% when taken during the 97-120 hour period (ie on day 5).3
In an earlier comparison study in 1546 women, a 50mg dose of ulipristal acetate was noninferior to two 0.75mg doses of levonorgestrel as an emergency contraceptive when taken up to 72 hours after unprotected intercourse. Analysis revealed that ulipristal prevented 85% of expected pregnancies.2,4
The efficacy of ulipristal has also been compared with that of levonorgestrel when taken up to 120 hours after unprotected intercourse (levonorgestrel is currently licensed for use only up to 72 hours after intercourse). Women aged 16 years were randomised to receive 30mg ulipristal acetate or 1.5mg levonorgestrel; 1899 participants were eligible for analysis. Reported pregnancy rates were 1.6% in women who were given ulipristal and 2.6% in those who received levonorgestrel, indicating that ulipristal prevented significantly more pregnancies than levonorgestrel (p<0.05).5
Combined analysis of the two comparison trials indicated that ulipristal was superior to levonorgestrel both overall (p=0.0253) and when used within 24 hours of unprotected sex (p=0.0346).4
In clinical trials, most adverse effects associated with ulipristal were mild or moderate, and resolved spontaneously.1 During the pivotal trial, 876 participants (61.4%) experienced an adverse event, most commonly headache (17.5%), nausea (12.2%) or abdominal pain (11.7%).2 Like levonorgestrel, ulipristal can slightly hasten or delay the next menstrual period.
Limited information is available about the effects of ulipristal on pregnancies that are pre-existing or which occur despite treatment. Consequently, use of the drug in women who are already pregnant is contraindicated.1 Ellaone's manufacturer is maintaining a registry to monitor outcomes of pregnancy in women exposed to the product. Prescribers should report, via the registry, any use of Ellaone in women who are subsequently found to be pregnant.
REFERENCES
- Ellaone Summary of Product Characteristics, 2009.
- CHMP Assessment Report for Ellaone. EMEA/261787/2009
- Fine P et al. Abstract presented at 8th Congress of the European Society of Gynecology. Rome, Italy, September 2009; SEG-005.
- Ulmann A et al. Abstract presented at 8th Congress of the European Society of Gynecology. Rome, Italy, September 2009; SEG-512.
- Cameron S et al. Abstract presented at 8th Congress of the European Society of Gynecology. Rome, Italy, September 2009; SEG-404.
Further information: HRA Pharma
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