Levonorgestrel alone is safer than the estrogen-containing preparations. There were several case reports of thrombotic events after use of the estrogen/levonorgestrel combination emergency contraception (268). No such complications with levonorgestrel alone were published.
Antiprogestins The antiprogesterone mifepristone (RU486) is highly effective for postcoital contraception. The usual abortifacient dose is 200 mg, but a dose of only 10 mg is effective for emergency contraception. In one study, 2,065 women were randomized to mifepristone, 10 mg, or levonorgestrel, two doses of 0.75 mg, including women up to 120 hours after intercourse (269). The crude pregnancy rate was 1.3% for mifepristone and 2.0% for levonorgestrel (p = .46). Side effects were the same, and both methods were judged highly acceptable by the patients. Mifepristone is not being developed for this use and is not available at the appropriate dose.
Ulipristal, a new progesterone-receptor modulator developed at the U.S. National Institutes of Health was approved by the FDA and the European Union for emergency contraception to 120 hours after intercourse. It is at least as effective as levonorgestrel 1.5 mg up to 72 hours, and may be superior between 72 and 120 hours (270). When Ulipristal is administered prior to the luteinizing hormone (LH) peak, it delays rupture of the preovulatory follicle for 5 days or more, which may be its primary mechanism of action (271). Ulipristal is primarily metabolized by the CYP3A4 enzyme system; hence, patients on drugs such as barbiturates, rifampin, and several of the anticonvulsants may have reduced protection from pregnancy with it. It is a prescription drug, while levonorgestrel 1.5 mg is available over the counter in the United States for women 18 years of age and over.
The Copper Intrauterine Device for Emergency Contraception
Postcoital insertion of a copper IUD was first reported by Lippes et al. in 1976 (272). In initial trials the device was inserted within 7 days of intercourse and was more effective than steroids for emergency contraception. Studies included women only within 5 days from intercourse. The multicenter trial by Wu and colleagues is an example of the superb efficacy offered by the copper T380A (273). Of 1,893 women who returned for a follow-up visit, there were no pregnancies within 1 month of IUD insertion. Efficacy for emergency contraception is 100% when the device is inserted up to 5 days after intercourse, and almost 100% up to 7 days after intercourse (273). An added benefit was that 94% of the patients were continuing with the IUD at the 12-month follow-up. There were no uterine perforations. Zhou and colleagues reported similar excellent results in a large study with a different copper device, the Multiload Cu-375 IUD (274). In much of the world, copper IUDs are very inexpensive. Even in the United States where IUDs are costly, the benefit to the patient of extremely effective emergency contraception, and long-term contraception with one intervention, makes emergency IUDs cost-effective. Whether the levonorgestrel IUD would work for emergency contraception is not known.