The Pharmaceutical Journal
Vol 269 No 7228 p838
14 December 2002

This article
Reprint
Photocopy

News summary

Related websites
The Lancet (www.thelancet.com)

Levonorgestrel not more effective than mifepristone

There are no differences in pregnancy rates between women who take levonorgestrel and those who use mifepristone for emergency contraception, researchers say. In addition, a single dose of levonorgestrel can be used as a substitute for a split-dose regimen.

Dr Helena von Hertzen and colleagues, from the World Health Organization research group on post-ovulatory methods of fertility regulation, randomly assigned 4,136 women with regular menstrual cycles, who requested emergency contraception within 120 hours of unprotected intercourse, to receive a single dose of mifepristone 10mg, a single dose of levonorgestrel 1.5mg or two doses of levonorgestrel 0.75mg given 12 hours apart. The trial was carried out in family planning clinics in 10 countries including the United Kingdom.

They conclude that all three regimens are efficacious for emergency contraception and prevent a high proportion of pregnancies if taken within five days of unprotected intercourse. Of the 4,071 women with known outcome, pregnancy occurred in 1.5 per cent (n=1,359) of women given mifepristone, 1.5 per cent (n=1,356) of those given single dose levonorgestrel and 1.8 per cent (n=1,356) of those given two doses of levonorgestrel. The relative risk of pregnancy for single dose levonorgestrel compared with two doses of levonorgestrel was 0.83 (95 per cent confidence interval, 0.46–1.5) and that for levonorgestrel (two regimens combined) compared with mifepristone was 1.05 (0.63–1.76).

Side effects did not differ greatly between the two groups and more than half the women in all groups menstruated within two days of the expected date. However, of the remaining women, more of those who took levonorgestrel had earlier bleeding than expected, whereas those who took mifepristone tended to have delayed bleeding. About 9 per cent (n=1,327) of women in the mifepristone group had a delay of more than seven days in the onset of first bleeding after treatment compared with 5 per cent for the levonorgestrel groups combined (n=2,666). The researchers comment that early bleeding is an advantage of both of the levonorgestrel regimens in that it relieves women from the anxiety associated with unwanted pregnancy sooner.

The researchers also confirm that there is a continued risk of pregnancy after treatment with mifepristone if women continue to have unprotected intercourse. They found a 22 per cent increase in pregnancy rate for those who continued to have intercourse compared with a 0.9 per cent increase for women who did not (Lancet 2002;1803:360).