naltrexone extended release

General information

• Class: Adjunctive therapy
• Common US brands: Vivitrol
• Typical dose range: Recommended dose is 380 mg as a deep IM gluteal injection every 4 weeks or once a month, alternating buttocks each injection (label).
• Therapeutic drug monitoring not routinely recommended.
• Last reviewed: 2026-02-12

Dosing & forms

• Forms/strengths: Injectable suspension containing 380 mg of naltrexone in a microsphere formulation (single-dose vial) (label).
• Frequency: Recommended dose is 380 mg as a deep IM gluteal injection every 4 weeks or once a month, alternating buttocks each injection (label).
• Typical range: Recommended dose is 380 mg as a deep IM gluteal injection every 4 weeks or once a month, alternating buttocks each injection (label).

Mechanism (brief)

Monthly extended-release injectable naltrexone (opioid antagonist) used for alcohol dependence and for opioid relapse prevention after detoxification. Requires an opioid-free interval to avoid precipitated withdrawal and carries important injection-site, hepatotoxicity, and overdose-vulnerability warnings (label/guideline).

Metabolism & Half‑life

• Metabolism: Extensive metabolism to 6β-naltrexol via dihydrodiol dehydrogenase (non-CYP) (label), Glucuronide conjugation (label)
• Half‑life: Single-dose range 120–240 h

Therapeutic Drug Monitoring (TDM)

Recommended: No

Monitoring highlights

• Confirm opioid-free status before initiation; plan for higher-risk transitions from methadone or buprenorphine (label/clinical).
• Monitor injection sites for severe reactions and ensure appropriate administration technique (deep IM gluteal) (label/clinical).
• Monitor liver symptoms and liver enzymes when indicated, especially in alcohol-related liver disease (label/clinical).
• Monitor mood and suicidality, particularly in patients with comorbid depression (label/clinical).
• Review overdose risk education and consider naloxone access planning (label/clinical).

Sources

• VIVITROL (naltrexone for extended-release injectable suspension) prescribing information — DailyMed (2026)
• The ASAM National Practice Guideline for the Treatment of Opioid Use Disorder: 2020 Focused Update — Journal of Addiction Medicine (2020)
• TIP 63: Medications for Opioid Use Disorder — SAMHSA (2021)
• Comparative effectiveness of extended-release naltrexone versus buprenorphine-naloxone for opioid relapse prevention (X:BOT): a multicentre, open-label, randomised controlled trial — The Lancet (2018)
• The American Psychiatric Association Practice Guideline for the Pharmacological Treatment of Patients With Alcohol Use Disorder — American Journal of Psychiatry (2018)