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The US Food and Drug Administration (FDA) has not approved any injectable contraceptives, but, in December 1990, it approved Norplant, an implantable contraceptive. Family planning providers insert 6 capsules, each with 36 mg levonorgestrel, in a fan shape under the dermis of the upper arm. Norplant protects against pregnancy for at least 5 years . Fecundity returns within 2 weeks after capsules' removal. The steady low levels of levonorgestrel keep down both luteinizing hormone and follicle stimulating hormone levels. It suppresses ovulation and thickens the cervical mucus. Contraindications of Norplant are active thromboembolism, undiagnosed genital bleeding, acute liver disease, liver tumors, and breast cancer. Phenytoin and other drugs which speed up liver metabolism reduce Norplant's efficacy. The leading side effect of Norplant is irregular bleeding patterns. Some less common side effects include headaches, nervousness, dizziness, and acne. First year continuation rates range from 76 to 99% and 25 to 78% for 5 years of use. More than 85% of Norplant users are satisfied. Both continuation and satisfaction are associated with patient counseling. Research and development of biodegradable and other nonbiodegradable implants is ongoing. The most common injectable contraceptive in the world is Depo-Provera. 150 mg of Depo-Provera every 3 months suppresses ovulation, deteriorates the endometrium, thickens cervical mucus, and reduces motility of the tubes, thereby providing adequate protection against pregnancy. Some research shows Depo-Provera use significantly increases the low-density lipoprotein to high-density lipoprotein ratio, thereby increasing the risk for atherogenesis. Effectiveness rates match those of Norplant. Norethindrone enanthate was the first injectable contraceptive. Even though 40 countries approve it, the US does not. Animal studies of injectable microspheres or microcapsules with either progestogen or progestogen and estrogen are in progress.
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PMID:Injectable and implantable contraceptives. 138 11

Depot medroxyprogesterone acetate (DMPA, Depo-Provera) is used for contraception by 8-9 million women in more than 90 countries, including the US, as of January 1993. Pharmacologically active levels of DMPA persist for 3-4 months following injection. A 150 mg dose is used most often for high contraceptive efficacy every 3 months. Norethindrone enanthate (NET-EN, Noristerat) is somewhat less widely used and is not marketed in the US. Injectables act primarily by inhibiting ovulation, lowering the levels of follicle-stimulating hormone and luteinizing hormone. Approximately 50% of women using DMPA for 1 year report amenorrhea whose occurrence is less frequent with NET-EN. Menstrual changes are the most frequent causes of discontinuation of injectables. In cases of heavy bleeding it is appropriate to undergo gynecological examination to rule out unrelated conditions, such as vaginitis, cervicitis, or cervical lesions. The use of conjugated estrogen (12.5-2.5 mg daily) for 10-21 days will minimize bleeding. Some women using injectables experience headache, dizziness, bloating of the abdomen or breast, and mood changes. Long-term use of DMPA or NET-EN can often result in 1-3 kg weight gain. The WHO Collaborative Study of Neoplasia and Steroid Contraceptives was launched in 1979 to examine cancer risks with the use of DMPA in Thailand, Mexico, and Kenya. The relative risk of breast cancer was 1.21, which was statistically not significant. In women diagnosed with breast cancer under age 35, short-term exposure to DMPA was associated with a slightly increased breast cancer risk, which, however, was not associated with duration of use. DMPA dramatically lowers the risk of endometrial cancer for at least eight years following discontinuation of its use. DMPA did not alter the risk of cervical cancer. Fertility returns in 70% of former users within 12 months; it is suitable for postpartum and lactating women, and provides other noncontraceptive benefits.
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PMID:Injectable contraception: the USA perspective. 1234 20