Implantable contraceptives

The currendy (ca 1992) marketed injectable and implantable contraceptives are designed to be effective for maximum periods of three months and five years, respectively. There is Htde evidence from programmatic or health reasons that an injectable formulation with a longer effective life span, eg, six months, would not be equally effective. The acceptabiUty and effectiveness of long-acting contraceptives may be determined by the means by which a community deUvers contraceptive products to the pubHc the active life of a product may be determined by economic rather than programmatic or health related factors. 

Implanted Contraceptives. Controlled release of contraceptive progestins also can be accompHshed by incorporating the dmg into an implantable cylinder or rod. The best known implant is Norplant, developed by the Population Council. Norplant is composed of six matchlike silastic cylinders with the progestogen levonorgestrel (11) incorporated on the inside of each cylinder. After implantation under the skin, the product can provide effective contraception for a period of five years (43,44). Since silastic is not biodegradable, the implant can be removed from a patient at any time. 

IMPLANT CONTRACEPTIVE SYSTEM. Levonorgestrel, a progestin, is available as an implant contraceptive system (Norplant System). Six capsules, each containing levonorgestrel, are implanted under local anestiiesia in die subdermal (below the skin) tissues of the mid-portion of die upper arm. The capsules provide contraceptive protection for 5 years but may be removed at any time at die request of the patient. See Table 52-3 for more information on ways to promote an optimal response when taking die contraceptive hormones. 

Women who particularly benefit from progestin-only methods, including minipills, are those who are breast-feeding, those who are intolerant to estrogens, and those with concomitant medical conditions in which estrogen is not recommended. Also injectable and implantable contraceptives are beneficial for women with compliance issues. 

Table 40-3 Some Oral and Implantable Contraceptive Agents in Use.1 ...

Hormonal Contraception (Oral, Parenteral, Implanted Contraceptives)... 

Only one implantable contraceptive preparation is available at present in the USA. Etonogestrel, also used in some oral contraceptives, is available in the subcutaneous implant form listed in Table 40-3. Several hormonal contraceptives are available as vaginal rings or intrauterine devices. Intramuscular injection of large doses of medroxyprogesterone also provides contraception of long duration. 

French RS, Cowan FM, Mansour DJ, Morris S, Procter T, Hughes D, Robinson A, Guillebaud J. Implantable contraceptives (subdermal implants and hormonally impregnated intrauterine systems) versus other forms of reversible contraceptives two systematic reviews to assess relative effectiveness, acceptability, tolerability and cost-effectiveness. Health Technol Assess 2000 4(7) 1-107. 

Diaz S, Pavez M, Moo-Young AJ, Bardin CW, Croxatto HB. Clinical trial with 3-keto-desogestrel subder-mal implants. Contraception 1991 44(4) 393AOS. 

Suarez AA, Brunt EM, Di Bisceglie AM. A 35-year-old woman with progesterone implant contraception and multiple hver masses. Semin Liver Dis 2001 21(3) 453-9. 

Croxatto HD, Diaz S, Rosati S, Croxatto HB. Adnexal complications in women under treatment with progestogen implants. Contraception 1975 12(6) 629-37. 

Glasier A. Implantable contraceptives for women effectiveness, discontinuation rates, return of fertility, and outcome of pregnancies. Contraception 2002 65(l) 29-37. 

Brache V, Faundes A, Alvarez F, Cochon L. Nonmenstrual adverse events during use of implantable contraceptives for women data from clinical trials. Contraception 2002 65(l) 63-74. 

Hickey M, d Arcangues C. Vaginal bleeding disturbances and implantable contraceptives. Contraception 2002 65(l) 75-84. 

Chompootaweep S, Kochagam E, Tang-Usaha J, Theppitaksak B, Dusitsin N. Experience of Thai women in Bangkok with Norplant-2 implants. Contraception 1998 58(4) 221-5. 

Diaz, S., et al. 1984. Fertility regulation in nursing women. VI. Contraceptive effectiveness of a subdermal progesterone implant. Contraception 30 311. 

Some limitations are that the amount of drug that can be injected in this fashion is fairly small and that the injected drug must not irritate or inflame the subcutaneous tissues. The subcutaneous route can also be used when certain types of drug preparations are implanted surgically beneath the skin, so that the drug is slowly dispersed from the implanted preparation and then absorbed into the bloodstream for prolonged periods of time.62,86 A common example of this form of subcutaneous administration is the use of implanted hormonal contraceptive products (e.g., Norplant).9,53 The use of these implantable contraceptives is discussed in more detail in Chapter 30. 

Meirik O, Fraser IS, d Arcangues C. WHO Consultation on Implantable Contraceptives for Women. Implantable contraceptives for women. Hum Reprod Update. 2003 9 49-59. 

Salhab, A.S., Shomaf, M.S., Gharaibeh, M.N., Amer, N.A. (1999). Effects of castor bean abstract and ricin A-chain on ovulation and implantation. Contraception 59 395-9. 

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