Generic Name

Vivitrol

Mechanism

• Opioid antagonist: Binds irreversibly to μ‑opioid receptors, blocking the effect of endogenous and exogenous opioids, preventing withdrawal and reducing the rewarding properties of opiates.
• Alcohol craving modulation: Inhibits the activation of opioid‑dependent neuropeptide Y and endogenous opioid release in the nucleus accumbens, thereby attenuating the reinforcing effects of alcohol.
• Prolonged receptor occupancy: The microsphere matrix provides a slow, continuous release that maintains therapeutic plasma concentrations for ~30 days.

Pharmacokinetics

Indications

• Opioid use disorder – maintenance therapy after induction onto oral naltrexone or after completion of opioid detoxification.
• Alcohol use disorder – maintenance therapy for reducing heavy drinking episodes in patients stabilized on psychosocial support.
• Adjunct to psychotherapy – often combined with Cognitive‑Behavioral Therapy or Motivational Interviewing.

Contraindications

• Acute or chronic hepatitis, cirrhosis, or liver failure.
• Known hypersensitivity to naltrexone, ethanol, or any component of the formulation.
• Ongoing opioid use: May precipitate severe withdrawal; ensure opioid detox (≥24–48 h opioid‑free) before first dose.
• Use with other opioid antagonists (e.g., naloxone) can induce withdrawal.
• Severe psychiatric instability: Monitor for depression, anxiety, or suicidal ideation, especially in AUD patients.

Warnings:
• Risk of hepatotoxicity (rare but potentially fatal).
• Possible precipitated withdrawal in patients who have recently used opioids.
• Not approved for acute opioid overdose or for patients who need rapid pain control.

Dosing

• Initial dose: 380 mg IM after confirming opioid withdrawal (e.g., 8‑score on Clinical Opiate Withdrawal Scale) or, for AUD, after a 24‑hour alcohol‑free period.
• Maintenance: 380 mg IM every 30 days; can be extended to 60 days if patient remains stable and adherent.
• Missed dose: If ≤7 days missed, administer next injection. If >7 days missed, re‑induce opioid withdrawal before next dose.
• Premedication: Not required; consider local anesthetic for injection site discomfort.
• Co‑administered meds: Avoid concomitant opioid analgesics or medications that induce CYP3A4 (may reduce efficacy).

Adverse Effects

Note: Monitor for signs of liver injury and counsel patients to seek immediate medical attention if jaundice or severe abdominal pain develops.

Monitoring

• Liver function tests (ALT, AST, bilirubin): baseline; then at 1, 2, 3, 4, 6, and 12 months.
• Mental status & depression scales (PHQ‑9) during treatment.
• Opioid withdrawal assessment: use COWS before first injection.
• Injection site inspection at each visit.
• Alcohol use monitoring (self‑report, breathalyzer) for AUD patients.
• Blood pressure & heart rate if patient has cardiovascular comorbidities.

Clinical Pearls

• Pre‑dose screening is critical: Verify complete opioid withdrawal before the first injection; consider a naloxone test dose if uncertain.
• Combination therapy outperforms monotherapy: Pair Vivitrol with psychosocial interventions for maximal remission rates.
• Adherence check: Since missed injections (>7 days) can lead to lapse, reinforce patient education on monthly clinic visits.
• Avoid concurrent opioids: Even small doses (e.g., tramadol) can precipitate withdrawal; coordinate pain management plans.
• Use in AUD with caution: Patients with severe liver disease or active depression require closer surveillance; consider alternative agents (e.g., acamprosate).
• Pregnancy & lactation: Not studied; avoid in pregnant or breastfeeding women unless benefits outweigh risks.
• Storage: Keep injectable vial at 2–8 °C; after reconstitution, keep refrigerated and use within 30 days.

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• *This card integrates pharmacologic fundamentals with practical prescribing cues to support evidence‑based practice for healthcare professionals and medical students.*