HORMONAL IMPLANTS - CONTRACEPTION FOR A NEW CENTURY

Subdermal implants are contraceptive systems that release low, stable amounts of synthetic progestins from Silastic or other materials for p eriods of months to several years. Unlike other hormonal delivery syst ems, they do not cause unnecessary peaks in progestin levels and do no t use estrogens, and thus their health risks are minimal. Norplant has been studied more extensively than any other subdermal contraceptive implant. More than 60,000 women have participated in clinical trials, which demonstrated that this approach is one of the most effective rev ersible contraceptive methods available (1% pregnancy rate in 5-year u sers). The implant also reduces the incidence of ectopic pregnancy to a level much below noncontraceptive users and about equivalent to TCu3 80A intrauterine device users. Exposure to the sustained, low dose of levonorgestrel delivered by Norplant has shown only minor metabolic ch anges, Side effects are minor but often bothersome, causing some disco ntinuation of the method. First-year continuation rates range from 76% to 90%. Fertility return after discontinuation is prompt. Difficulty in removal of the implant capsules by the less experienced practitione r has motivated researchers to develop systems that are easier to use, less obvious under the skin, and biodegradable. The Norplant 2 system is faster, easier, and less painful to insert and remove. Implants un der investigation release desogestrel and other progestins; Capronor a nd subdermal norethindrone pellets are biodegradable systems.