Filler

Which postcoital contraceptive?

A few weeks ago my senior partner presented the results of a paper published in the Lancet1 comparing the standard Yuzpe method for postcoital contraception (combined oestrogen and progesterone) with two doses of progesterone only (levonorgestrel 0.75 mg). Until now the latter has required women to take large numbers of tablets, but a formulation in two single tablets has become available in the United Kingdom (Levonelle-2). A large number of women requesting emergency contraception were studied, 1998 enrolled, and the outcomes were known for 1955 of these. The results seemed to be quite clear cut: fewer pregnancies following the progesterone only regimen and also fewer adverse effects.

The overall pregnancy rate was found to be 3.2% of women given Yuzpe but only 1.1% of those randomised to levonorgestrel. This represents a relative risk of 0.36, and the size of the trial meant that the 95% confidence interval of 0.18 to 0.70 was narrow enough to exclude the null hypothesis of no difference between treatments. Vomiting was also significantly less common, occurring in 19% of women given the Yuzpe regimen and 6% given levonorgestrel (p<0.01).

A single study may be contradicted by other trials, so I decided to check this out further in the Cochrane Library and found a review covering emergency contraception which was updated in March 1999.2 The review found two randomised controlled trials which compared levonorgestrel and Yuzpe (including the World Health Organization study in the Lancet). The results of the two studies were similar, and the pooled relative risk of pregnancy with levonorgestrel was 0.51 (95% CI 0.31 to 0.84) when compared with Yuzpe. The pooled risk of pregnancy with the Yuzpe regimen is 3.2% across the two trials, so the number needed to treat with levonorgestrel rather than Yuzpe to prevent one pregnancy is 63 (95% CI 45-193). Similarly, since levonorgestrel induces fewer side effects, only seven patients need to be given this rather than Yuzpe (95% CI 7-8) to prevent one from vomiting.

Although the new treatment is more expensive, we estimated that switching to levonorgestrel from Yuzpe would cost about £200 per extra pregnancy prevented. This compares favourably with the cost and inconvenience of a termination of pregnancy which would otherwise be needed after failed postcoital contraception. We have changed our practice.

Christopher Cates, general practitioner, Watford. 

1   Task Force on Postovulatory Methods of Fertility Regulation. Randomised controlled trial of levonorgestrel versus Yuzpe regimen of combined oral contraceptives for emergency contraception. Lancet 1998;352:428-33. 2   Cheng L, Gülmezoglu AM, Ezcurra E, Van Look PFA. Interventions for emergency contraception. (Cochrane Review). In: Cochrane Library, Issue 2. Oxford: Update Software, 2000.