Injectable and implantable contraceptives.

ABSTRACT

PIP: 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.