Randomised controlled trial of levonorgestrel versus the Yuzpe regimen
of combined oral contraceptives for emergency contraception

Task Force on Postovulatory Methods of Fertility Regulation

Summary



Background – A previous randomised study suggested
that the progestagen, levonorgestrel, given alone in two separate
doses each of 0.75 mg caused nausea and vomiting in fewer women and
might be more effective than the Yuzpe regimen of combined oral contraceptives
for emergency contraception, although the difference was not significant.
We compared these two regimens when started within 72 h of unprotected
coitus.

Methods – We enrolled in the double-blind, randomsed
trial 1998 women at 21 centres worldwide. Women with regular menses,
not using hormonal contraception, and requesting emergency contraception
after one unprotected coitus, received levonorgestrel (0.75 mg, repeated
12 h later) or the Yuzpe regimen (ethinyloestradiol 100 ?g plus levonorgesterel
0.5 mg, repeated 12 h later).

Findings – Outcome was unknows for 43 women (25 assigned
levonorgestrel, 18 assigned Yuzpe regimen). Among the remaining 1955
women, the crude pregnancy rate was 1.1% (11/976) in the levenorgesterel
group compared with 3.2% (31/979) in the Yuzpe regimen group. The
crude relative risk of pregnancy for levonorgestrel compared with
the Yuzpe regimen was 0.36 (95% CI 0-18-0-70). The proportion of pregnancies
prevented (compared with the expected number without treatment) was
85% (74-93) with the levonorgestrol regimen and 57% (39-71) with the
Yuzpe regimen. Nausea (23.1 vs 50.5%) and vomiting (5.6 vs 18.8%)
were significantly less frequent with the levonorgestrel regimen than
with the Yuzpe regimen (p < 0.01). The efficacy of both treatments
declined with increasing time since unprotected coitus (p = 0.01).

Interpretation – The levonogestrel regimen was better tolerated
and more effective than the current standard in hormonal emergency
contraception. With either regimen, the earlier the treatment is given,
the more effective it seems to be.

Lancet 1998;352:428-33