Implantable hormonal contraception is one of the most effective methods of contraception available. The initial concept of implant contraception based on Silastic polymer capsules was proposed in 1967.<sup>134 Segal SJ, Croxatto HB Single administration of hormones for long term control of reproductive function. Presented at the XXIII Meeting of American Fertility Society, Washington, DC, 1967

Cliccare qui per andare alla sezione Riferimenti</sup> Twenty years of research by the Population Council determined the metabolic and pharmacologic effects, most suitable progestin, carrier, dose, efficacy, side effects, acceptability, and mechanisms of action before the first implant, Norplant (Schering-Leiras, Berlin), was endorsed by the World Health Organization (WHO) in 1985. Another 5 years passed before the US Food and Drug Association (FDA) approved Norplant for use in the United States, the 20th country to adopt the new method.

The experiences of more than 6 million users of Norplant worldwide<sup>75 Fraser I.S., Tiitinen A., Affandi B. , e al. Norplant consensus statement and background review Contraception 1998 ;  57 : 1

Cliccare qui per andare alla sezione Riferimenti</sup> have led to improvements and new implants. Many of the innovations simplify removal, which can sometimes be painful and time-consuming with Norplant.<sup>73 Frank M.L., Poindexter A.N.d., Cornin L.M. , e al. One-year experience with subdermal contraceptive implants in the United States Contraception 1993 ;  48 : 229

Cliccare qui per andare alla sezione Riferimenti</sup> Delivery systems now use only one or two implants rather than six because new polymers and mixtures allow controlled release of the progestin from a smaller surface area. Some implants combine carrier and progestin in a solid rod, whereas others surround the progestin with a carrier capsule. In this review, the word “capsule” may refer to both carrier types. Biodegradable capsules and pellets are also under investigation. Implants with newer low-androgenic progestins may decrease side effects such as acne and mood or weight changes. Implanon (Organon, Oss, Netherlands) is a new single-rod implant that releases etonogestrel, the active metabolite of desogestrel, the progestin in the oral contraceptives Desogen (Organon), Ortho-cept (Ortho, Raritan, NJ), and Mircette (Organon).

Implants are an important option for women who have problems with other types of birth control. Implants have worked well for adolescents and injection drug users<sup>46 Darney P.D., Atkinson E., Tanner S. , e al. Acceptance and perceptions of Norplant among users in San Francisco, USA Stud Fam Plann 1990 ;  21 : 152  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> and for other women who may not do well with coitus-dependent or memory-dependent methods or intrauterine devices (IUDs). Implants can be used in breastfeeding women and older women with cardiovascular risk factors such as smoking. Because implants do not contain estrogen, they are appropriate for some women who have contraindications to combined oral contraceptives, such as a history of thrombophlebitis or pulmonary embolism.<sup>180 World Health Organization   Improving Access to Quality Care in Family Planning: Medical Eligibility Criteria for Contraceptive Use Geneva: World Health Organization (1996). 

Cliccare qui per andare alla sezione Riferimenti</sup> Studies have shown no increased risk of cardiovascular disease with progestin-only contraceptives.<sup>104 McCann M.F., Potter L.S. Progestin-only oral contraception: A comprehensive review Contraception 1994 ;  50 : S1

Cliccare qui per andare alla sezione Riferimenti</sup> Although earlier investigations suggested decreased efficacy in heavier women (>70 kg), studies of new implants<sup>42 Croxatto H.B., Urbancsek J., Massai R. , e al. A multicentre efficacy and safety study of the single contraceptive implant Implanon. Implanon Study Group Hum Reprod 1999 ;  14 : 976  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> and of the current Norplant formulation show good efficacy in heavy women.<sup>161 Sivin I., Viegas O., Campodonico I. , e al. Clinical performance of a new two-rod levonorgestrel contraceptive implant: A three-year randomized study with Norplant implants as controls Contraception 1997 ;  55 : 73

Cliccare qui per andare alla sezione Riferimenti</sup> Unlike the injectable depot medroxyprogesterone acetate (DMPA), implants do not decrease bone density with prolonged use.<sup>35 Cromer B.A., Blair J.M., Mahan J.D. , e al. A prospective comparison of bone density in adolescent girls receiving depot medroxyprogesterone acetate (Depo-Provera), levonorgestrel (Norplant), or oral contraceptives J Pediatr 1996 ;  129 : 671  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti, 108 Naessen T., Olsson S.E., Gudmundson J. Differential effects on bone density of progestogen-only methods for contraception in premenopausal women Contraception 1995 ;  52 : 35  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> Implants have the potential to decrease menstrual blood loss, anemia, the risk for upper genital tract infection, and pain associated with endometriosis.

One of the primary disadvantages of implants is the surgical procedure required to begin and end their use. Removal can be difficult if the capsules are inserted too deeply and may require more than one visit. Newer systems decrease the difficulty and removal time by employing only one or two implants. The provider-dependent aspect of removal has led to concerns about the potential for coercion if requests for removal are denied. Menstrual disruption is the most common side effect and leads to many early discontinuations.

Women who use implants generally report a high degree of satisfaction.<sup>116 Ortho Pharmaceutical Corporation   Annual Birth Control Study Raritan, NJ: Ortho Pharmaceutical Corporation (1994). 

Cliccare qui per andare alla sezione Riferimenti</sup> Women can elect up to 7 years of effective, reversible contraception with just one decision. Implants are not coitus-dependent, are immediately reversible with removal, and deliver the lowest dose of progestin that can provide effective contraception, less than 25% of the amount in oral contraceptives.<sup>84 Hatcher R.A. Depo-Provera, Norplant, and progestin-only pills (minipills) Contraceptive Technology Cooper Station, NY: Ardent Media (1998). 

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