Extending the Time Limit for Starting the Yuzpe Regimen of Emergency Contraception to 120 Hours

Abstract

In conjunction with a study of modifications to the Yuzpe regimen of emergency contraception delivered with 72 hours of unprotected intercourse, the authors conducted a second prospective trial that investigated the efficacy of the regimen beyond 72 hours. Both trials accepted women aged 16-45 years (in the United States, 18-45 years) with regular menstrual cycles who had unprotected intercourse between 10 days before and 6 days after expected ovulation and who refused a copper intrauterine device. Participants had to be willing to abstain from unprotected intercourse during the study cycle and willing to return for a follow-up visit. The Yuzpe regimen used consisted of 100 μg of ethanol estradiol plus 1.0 mg of norgestrel repeated after 12 hours. Study patients were women who presented 4-5 days after unprotected intercourse (n = 111); women enrolled in the first trial served as control subjects (n = 675). Overall, 3.7% (4 of 111) of women treated in the extended time period became pregnant compared with 2.5% of control subjects (17 of 675), but the difference was not significant. It was determined that 2 (1.9%) study patients and 12 (2.5%) patients in the control group had followed the regimen perfectly. Women who strayed from the prescribed standard 2-dose regimen were considered typical users. Perfect use of the regimen within 1-3 days prevented 77% expected pregnancies in women who received no intervening therapy after unprotected intercourse, and perfect use within 3-4 days prevented 73% of expected pregnancies.