IMPLANTABLE CONTRACEPTION - 06/09/11
Resumen |
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 1967.134 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 worldwide75 have led to improvements and new implants. Many of the innovations simplify removal, which can sometimes be painful and time-consuming with Norplant.73 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 users46 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.180 Studies have shown no increased risk of cardiovascular disease with progestin-only contraceptives.104 Although earlier investigations suggested decreased efficacy in heavier women (>70 kg), studies of new implants42 and of the current Norplant formulation show good efficacy in heavy women.161 Unlike the injectable depot medroxyprogesterone acetate (DMPA), implants do not decrease bone density with prolonged use.35, 108 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.116 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.84
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| Address reprint requests to Karen R. Meckstroth, MDDepartment of Obstetrics, Gynecology, and Reproductive SciencesUniversity of California San FranciscoSan Francisco General Hospital, Ward 6D-11001 Portrero AvenueSan Francisco, CA 94110 |
Vol 27 - N° 4
P. 781-815 - décembre 2000 Regresar al número
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- INJECTABLE CONTRACEPTION : New and Existing Options
- Andrew M. Kaunitz
- EMERGENCY CONTRACEPTION
- June LaValleur
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