Nexplanon
Nexplanon
Generic Name
Nexplanon
Mechanism
Nexplanon is a subdermal contraceptive implant that delivers the progestin etonogestrel at a low, constant rate (~0.3 µg/day).
• Uterine effect: Etonogestrel thickens cervical mucus, inhibiting sperm penetration; it suppresses endometrial proliferation, preventing implantation.
• Ovarian effect: Sustained progestin levels suppress the hypothalamic‑pituitary‑gonadal axis, inhibiting the mid‑cycle LH surge and thus ovulation.
• Pharmacologic profile: Because of its slow, continuous release from a flexible silicone device, it maintains therapeutic concentrations for up to 3 years with minimal systemic fluctuations.
Pharmacokinetics
| Parameter | Typical value for Nexplanon |
| Absorption | Subdermal route → peak plasma levels within 1–3 months; steady‑state 3–4 months |
| Volume of distribution | Large; 120–140 L (highly lipophilic) |
| Metabolism | Primarily hepatic CYP3A4-mediated 11β‑hydroxylation → inactive 1‑O‑acetyl‑etonogestrel |
| Clearance | Renal (minor) and hepatic; dose‑independent |
| Half‑life | Plasma t½ ~2–4 days; effective tissue residence >3 years |
| Inter‑patient variability | Minor; influenced by hepatic enzyme induction (e.g., St. John’s wort) or inhibition (e.g., azole antifungals) |
Key point: Drug–drug interactions that alter CYP3A4 activity can lead to sub‑therapeutic or supratherapeutic etonogestrel levels.
Indications
- Highly effective reversible contraception for women aged 12–50 years, non‑parous or parous.
- Extended‑release implant providing ≥99 % efficacy for up to 3 years.
- Particularly useful for patients desiring a low‑maintenance, “set‑and‑forget” method (e.g., college students, traveling, postpartum).
Contraindications
Contraindications
• Known hypersensitivity to etonogestrel or device components.
• Active thromboembolic disease or thrombophilia.
• Recent or ongoing pregnancy, known pregnancy.
• Breastfeeding in the first 3 days postpartum (risk of lactation suppression).
Warnings
• Venous thromboembolism: Slightly increased risk; assess personal and family history.
• Bone density: Prolonged use may decrease bone mineral density; monitor in women with osteoporosis risk factors.
• Breast cancer: Avoid in women with personal history of estrogen‑dependent breast cancer.
• Pediatric use: Not approved for children under 12.
Dosing
- Single implant: 2.54 mm × 12 mm silicone rod.
- Procedure: Inserted subdermally into the inner upper arm; insertion is performed by trained clinician.
- No pre‑treatment or post‑treatment medication required.
- Removal: Device can be withdrawn after 3 years or earlier if contraception discontinued; residual implantation risk if removed after 2 years (~5 % chance).
Adverse Effects
| Category | Symptoms |
| Common | Irregular bleeding, spotting, amenorrhea, cyclical headache, mood changes, acne, temporary weight gain |
| Serious | – Thromboembolic events (deep vein thrombosis, pulmonary embolism) < 2/10 000 – Breast tenderness or lactation suppression in lactating mothers – Skin irritation, local infection at insertion site – Rare: device expulsion or migration |
Management
• Mild bleeding: NSAIDs; consider combined oral contraceptives for short periods.
• Thrombotic events: Immediate anticoagulation and removal of device.
Monitoring
| Parameter | Frequency | Rationale |
| Baseline CBC, CBC with smear | Prior to insertion | Detect anemia or cytopenias |
| Blood pressure | Post‑insertion and annually | Hypertension may increase thrombotic risk |
| Screening for thrombophilia | In high‑risk patients | Identify predisposition to VTE |
| Breast exam | Yearly | Monitor for changes or lactation status |
| Bone density (DXA) | In high‑risk patients or after ≥2 years | Evaluate chronic bone loss |
| Adverse event surveillance | Every visit | Early detection of device‐related complications |
Clinical Pearls
- Insertion site choice matters: The inner upper arm offers high patient satisfaction; avoid sites with pre‑existing trauma or infections.
- Breastfeeding timing: Breastfeeding for ≥3 days postpartum allows safe implant placement; otherwise, plan for a different method.
- Device migration: Rare but possible; if removal is delayed (>3 yrs), surgical removal may be required due to increased fibrotic encapsulation.
- Drug interactions: Azole antifungals (ketoconazole, fluconazole) and strong CYP3A4 inducers (rifampin) can lower etonogestrel levels → consider switching to a different method.
- Patient counseling: Emphasize the *“no‑requirement”* nature but re‑educate on potential irregular bleeding; reassurance reduces early discontinuation.
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• Quick Reference Table
| Feature | Detail |
| Brand | Nexplanon® (Etonogestrel implant) |
| Release | 0.3 µg/day (continuous) |
| Duration | Up to 3 years |
| Efficacy | 99.9 % TFR |
| Route | Subdermal |
| Key Active | Etonogestrel (progestin) |
This concise, keyword‑rich drug card serves as an essential reference for medical students and clinicians seeking rapid, evidence‑based facts on Nexplanon.