Etonogestrel Implant

• Contraception (Birth Control)
• Long-Acting Reversible Contraception
• Pregnancy Prevention
• Family Planning

The etonogestrel implant is a long-acting reversible contraceptive (LARC) that provides highly effective birth control for up to 3-5 years through continuous release of a progestin hormone from a single subdermal rod. This method offers convenience and effectiveness without requiring daily user action.

Mechanism of Action

Etonogestrel is a progestin (the active metabolite of desogestrel) that provides contraception through multiple mechanisms. The primary mechanism is suppression of ovulation by inhibiting the luteinizing hormone (LH) surge. Additionally, etonogestrel thickens cervical mucus, inhibiting sperm penetration and transport, and causes changes in the endometrium that may reduce the likelihood of implantation. The implant releases approximately 60-70 mcg/day initially, decreasing to 35-45 mcg/day by the end of the first year and further to 25-30 mcg/day by the end of the third year. Despite declining hormone levels, contraceptive efficacy is maintained throughout the labeled duration.

Available Formulations

The etonogestrel implant (Nexplanon) is a single, radiopaque, 4 cm by 2 mm ethylene vinyl acetate copolymer rod containing 68 mg of etonogestrel. It is preloaded in a sterile, disposable applicator for subdermal insertion. The implant is radiopaque due to barium sulfate content, allowing visualization on X-ray if needed for localization. It replaces the earlier Implanon device, which was not radiopaque.

Medical Uses

The etonogestrel implant is FDA-approved for prevention of pregnancy in women of reproductive potential. With a failure rate of less than 0.1%, it is one of the most effective contraceptive methods available—more effective than permanent sterilization procedures. The implant is particularly suitable for women desiring long-acting contraception, those who have difficulty remembering daily or weekly methods, and those who cannot use estrogen-containing contraceptives. It can be inserted immediately postpartum.

Dosing Guidelines

The implant is inserted subdermally on the inner side of the upper arm, 8-10 cm above the medial epicondyle of the humerus, by a trained healthcare provider. Insertion should occur during days 1-5 of the menstrual cycle (no backup contraception needed), or at any time if reasonably certain the patient is not pregnant (7 days of backup needed). The implant is effective for up to 3 years (some data support up to 5 years). Removal should be performed by a trained provider using a small incision.

Important Safety Information

The implant should not be used in women with current or history of breast cancer, known or suspected pregnancy, undiagnosed abnormal genital bleeding, current or history of thrombosis or thromboembolic disorders, hepatic tumors or active liver disease, hypersensitivity to any component, or current use of hepatic enzyme-inducing medications. Deep insertion or migration can make localization and removal difficult; insertion should always be palpable subdermally. Irregular bleeding is common and is the most frequent reason for discontinuation.

Drug Interactions

Hepatic enzyme-inducing drugs (certain anticonvulsants: carbamazepine, phenytoin, phenobarbital; certain HIV medications: efavirenz, nevirapine; rifampin; St. John's Wort) may decrease etonogestrel effectiveness, potentially leading to contraceptive failure or breakthrough bleeding. Women on long-term therapy with these medications should consider alternative contraceptive methods. Non-enzyme-inducing alternatives should be chosen when possible.

Special Populations

The implant is contraindicated in known or suspected pregnancy, though removal is not necessary if pregnancy occurs. It can be inserted immediately postpartum in non-breastfeeding women. In breastfeeding women, insertion can occur at 4-6 weeks postpartum (earlier if medically appropriate). The medication is not indicated for pediatric use before menarche. No specific age restrictions exist for older reproductive-age women. The implant does not affect bone mineral density as some other progestin-only methods do. No dose adjustment is needed for renal impairment. Avoid use in patients with hepatic impairment or liver tumors.