Original researchModifying the Yuzpe regimen of emergency contraception: a multicenter randomized controlled trial☆
Section snippets
Must the progestin be levonorgestrel?
Ideally, women could use any oral contraceptive postcoitally. We tested a formulation that substitutes norethindrone for levonorgestrel. Norethindrone is the progestin with the shortest serum half-life (7 hours), whereas levonorgestrel has the longest (15 hours).7 Therefore, if norethindrone works, other progestins might also. If effective, additional formulations could expand access. The exact brand studied in Yuzpe’s original trials currently has only a tiny market share, as lower estrogen
Materials and methods
We conducted a double-masked, multicenter randomized controlled trial.12 Between September 1997 and February 2000, emergency contraception clients presenting at one of five clinic sites in the United States (Des Moines) and the United Kingdom (Liverpool, Glasgow, and, later, Sheffield and Edinburgh) and meeting strict eligibility criteria could participate. Women age 16–45 years (18–45 in the United States) could enroll if they had regular cycles varying between 21 and 35 days in length,
Results
We enrolled 2041 women at five centers (Table 1). Of these, 11 (four in the Yuzpe control group, two in the norethindrone group, and five in the single dose group) turned out to have been enrolled mistakenly (mainly because their cycle days of exposure were calculated wrong). None of the 11 became pregnant, and all are retained in our intention-to-treat analysis of effectiveness.
Two thirds of participants reported that burst condoms led them to need emergency contraception, whereas a further
Discussion
Although the standard Yuzpe regimen had the lowest failure rate of those tested in our trial, we found clear evidence that a regimen substituting more widely available brands of combined oral contraceptives containing norethindrone instead of levonorgestrel is safe and effective. Women lacking access to levonorgestrel-only or standard Yuzpe preparations (as is unfortunately the case for hundreds of millions of women around the world) could certainly use norethindrone–ethinyl estradiol brands.
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The authors represent a larger study team that includes Katrina Abuabara, Sarah Carlson, Margaret Evans, Sue Ferden, Joanne Gallagher, Anna Glasier, Bridget Hinchcliffe, Chris Hesketh, Janice Hunt, Karen Johnston, Helen King, Clare Leadbetter, Becca Loftus-Granberg, Chris McCaig, Abigail Norris Turner, Annik Sorhaindo, Aileen Spears, Alex Stirling, Anne Tyrer, and Kate Weaver.
The trial was supported by grants from the William and Flora Hewlett Foundation, David & Lucile Packard Foundation, Open Society Institute, Mary Wohlford, John Snyder, the Population Council, an anonymous donor, and Irving and Roberta Schneiderman. Funders did not participate in implementing any stage of the study.