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Can Fam Physician. 1999 Mar;45:629-31.

Levonorgestrel versus the "Yuzpe" regimen. New choices in emergency contraception.

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Department of Family and Community Medicine, University of Toronto.



A double-blind, randomized controlled trial conducted at 21 centers in 14 countries compared the effectiveness and side effects of the traditional Yuzpe method of emergency contraception (200 mcg of ethinyl estradiol and 1 mg of levonorgestrel divided into 2 equal doses) and levonorgestrel alone (2 doses of 0.75 mg each). 1955 women (979 in the Yuzpe group and 976 in the levonorgestrel group) completed the study. 42 women had subsequent pregnancies, although at least 4 women were pregnant at the time of treatment. The pregnancy rate was 1.1% (95% confidence interval [CI], 0.6-2.0) for the levonorgestrel group and 3.2% (95% CI, 2.2-3.5) for the Yuzpe regimen. The relative risk of pregnancy was 0.36 (95% CI, 0.18-0.70). Levonorgestrel prevented 85% of expected pregnancies while the Yuzpe method prevented only 57%. Efficacy increased when the regimen was initiated within 24 hours and decreased as the time after unprotected intercourse approached 72 hours. Women in the levonorgestrel group reported less nausea, vomiting, dizziness, and fatigue than their counterparts in the Yuzpe group. Overall, 57% of women started bleeding within 3 days of their expected menses and the mean duration of menses of 4.7 days in both groups. Results of this study support use of levonorgestrel alone as an alternative for emergency contraception.

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