Implanon: A Critical Review

Prevention of unintended pregnancy through contracep-tion is critical for family planning as well as in elimi-nating the need for high-risk abortions and deaths from re-lated complications. This is especially important in the adolescent population.1,2 Long-acting implantable methods of contraception, such as Norplant, are cost-effective when compared with the cost of unplanned pregnancy.3,4 The search for effective contraceptive methods is targeted at re-ducing costs and risks associated with abortions and preg-nancy. Implants offer the most effective contraception, with an expected and typical failure rate of 0.035 % (Table 1).5 This is eight times less than the expected rate of acci-dental pregnancy and 85 times less than the failure rate of oral contraceptives. One reason for the success of long-act-ing implants is that compliance is not a concern, unlike with oral contraceptives and condoms. Contraceptive im-plants are associated with a high, one-year continuation rate,6 and are also more cost-effective compared with oral contraceptives.3,6 Natural progestins are released by the corpus luteum and stimulate endometrial progression from the follicular to the secretory phase. Synthetic compounds are being de-veloped with reduced androgenic activity and increased potency. The benefits of progestin-only implants include a long duration of action, short fertility recovery time after removal, protection against endometrial and ovarian can-cer, and decreased incidence of pelvic inflammatory dis-ease and vulvovaginal candidiasis.7 One of the most useful roles for progestin-only implants is in situations where ex-ogenous estrogens are contraindicated. Norplant, the cur-rently available implant, contains a progestin within a sus-tained-release system that delivers therapeutic concentra