Etonogestrel Implant

Generic Name: Etonogestrel

Brand Names: Nexplanon

Nexplanon is a long-acting reversible contraceptive implant providing 3 years of pregnancy prevention with a single small rod inserted under the skin.

Women's HealthContraceptionLong-Acting Contraception

Drug Class

Progestin-Only Long-Acting Reversible Contraceptive (LARC) — Subdermal Implant

Pregnancy

Category X — Contraindicated in known or suspected pregnancy. Although limited data have not shown teratogenic effects from inadvertent exposure during early pregnancy, there is no indication for use in pregnant women. Confirm pregnancy is excluded before insertion.

Available Forms

Subdermal radiopaque implant — single 4 cm rod containing 68 mg etonogestrel (Nexplanon), preloaded in disposable applicator

What It's Used For

Dosage Quick Reference

These are general dosage guidelines. Your doctor will determine the appropriate dose for your specific situation.

Indication	Insertion	Replacement
Contraception (never used hormonal contraception in past month)	Insert subdermally in non-dominant upper arm during days 1–5 of menstrual cycle	Replace every 3 years (FDA-approved); evidence supports up to 5 years
Switching from combined hormonal contraceptive	Insert anytime, ideally within 7 days of last active hormone	Replace every 3 years
Switching from progestin-only pill	Insert any day; no backup contraception needed if pill taken consistently	Replace every 3 years
Postpartum (non-breastfeeding)	Insert anytime, ideally within 21 days postpartum	Replace every 3 years
Postpartum (breastfeeding)	Insert after 4 weeks postpartum (per ACOG, may be inserted earlier)	Replace every 3 years

Side Effects

Common Side Effects:

Irregular menstrual bleeding (most common reason for discontinuation)
Amenorrhea
Headache
Weight gain
Acne
Breast tenderness
Mood changes
Abdominal pain
Insertion site reactions

Serious Side Effects:

Ectopic pregnancy (if pregnancy occurs)
Thrombotic events (rare)
Complications from deep insertion or migration
Ovarian cysts
Depression
Allergic reactions

Drug Interactions

Etonogestrel is metabolized by CYP3A4. Drugs that induce this enzyme can reduce contraceptive efficacy.

Strong CYP3A4 inducers (rifampin, rifabutin, phenytoin, carbamazepine, phenobarbital, primidone, topiramate at doses > 200 mg/day): Significantly reduce etonogestrel plasma concentrations, potentially causing contraceptive failure. Use a backup non-hormonal method (condoms) during therapy and for 28 days after discontinuation, or choose an alternative contraceptive method.
St. John wort (Hypericum perforatum): Induces CYP3A4 and may reduce implant effectiveness. Patients should avoid this herbal supplement or use backup contraception.
Certain HIV protease inhibitors (e.g., nelfinavir, ritonavir-boosted regimens): Effects on etonogestrel are variable; some increase and some decrease levels. Consult HIV-pharmacology resources or a pharmacist when starting antiretroviral therapy.
Certain anticonvulsants without enzyme induction (lamotrigine, valproate, gabapentin, levetiracetam): Generally do not reduce implant efficacy and are preferred when seizure control allows.
Bosentan: A moderate CYP3A4 inducer that may reduce etonogestrel levels. Consider a backup or alternative contraceptive method.

Additional Information

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.

Frequently Asked Questions

The implant is one of the most effective contraceptives available, with a failure rate of less than 1 in 1,000 users per year — comparable to female sterilization and more effective than oral contraceptives or condoms in real-world use. Effectiveness is not dependent on user adherence, which removes the main cause of failure with daily methods.

Bleeding patterns become unpredictable for most users. About 1 in 5 women stop having periods entirely, while others experience irregular spotting or, less commonly, prolonged or frequent bleeding. The pattern in the first 3 months tends to predict the long-term pattern. Irregular bleeding is the most common reason for early removal but is not medically harmful.

Fertility returns rapidly after removal — most women resume ovulation within 3 to 4 weeks. Pregnancy rates in the year following removal are similar to those of women who never used hormonal contraception. There is no evidence that the implant causes long-term fertility impairment.

A local anesthetic is injected at the insertion site to numb the skin. Most women describe the procedure as quick (under 1 minute) with mild pressure rather than pain. Mild bruising, swelling, or tenderness at the site is common for a few days. Removal involves a small incision and is similarly brief.

Significant migration is rare with proper insertion technique. The Nexplanon implant is radiopaque, meaning it can be located by X-ray, ultrasound, or MRI if it cannot be palpated. You should be able to feel the implant under the skin at all times. Contact your provider if you cannot locate it or if it appears to have moved significantly.

No. The implant prevents pregnancy but provides no protection against STIs including HIV, gonorrhea, chlamydia, syphilis, or herpes. Condoms remain necessary for STI prevention with new or non-monogamous partners.

Questions to Ask Your Doctor

Consider discussing these topics at your next appointment:

✓Is the implant a good fit for me given my medical history and lifestyle?
✓What bleeding pattern should I expect, and when should I be concerned?
✓How will my other medications affect the implant effectiveness?
✓What are my options if I want the implant removed before 3 years?
✓How do I check that the implant is still in place between visits?

Schedule an Appointment

Medical Disclaimer: This information is for educational purposes only and should not be considered medical advice. Always consult with your healthcare provider before starting, stopping, or changing any medication. Your doctor can provide personalized recommendations based on your specific health condition and medical history.