Naltrexone
Generic Name: Naltrexone
Brand Names: ReVia, Vivitrol
Naltrexone is an opioid antagonist used for alcohol use disorder and opioid use disorder. Blocks effects of opioids and reduces alcohol cravings.
Drug Class
Opioid Antagonist
Pregnancy
Category C (oral); no adequate well-controlled studies in pregnant women. Animal studies have shown adverse effects on the fetus. Use only if the potential benefit justifies the potential risk to the fetus.
Available Forms
50 mg oral tablet, 380 mg/vial extended-release intramuscular suspension (Vivitrol)
What It's Used For
Dosage Quick Reference
These are general dosage guidelines. Your doctor will determine the appropriate dose for your specific situation.
| Condition | Starting Dose | Maintenance Dose |
|---|---|---|
| Alcohol Dependence (oral) | 25 mg once daily for the first day to assess tolerability | 50 mg once daily |
| Alcohol Dependence (IM injection) | 380 mg IM into gluteal muscle once | 380 mg IM every 4 weeks, alternating buttocks |
| Opioid Dependence (oral) | 25 mg initially; patient must be opioid-free 7-10 days | 50 mg once daily (or 100 mg Mon/Wed, 150 mg Fri for supervised dosing) |
Side Effects
Common Side Effects:
- Nausea (most common initially)
- Headache
- Dizziness
- Fatigue
- Anxiety
- Insomnia
- Injection site reactions (IM form)
Serious Side Effects:
- Hepatotoxicity
- Precipitated opioid withdrawal
- Depression and suicidal ideation
- Eosinophilic pneumonia (rare)
Drug Interactions
- Opioid analgesics (morphine, oxycodone, hydrocodone, fentanyl): Naltrexone blocks opioid receptors and will precipitate acute withdrawal in opioid-dependent patients. Patients must be opioid-free for at least 7 to 10 days before starting naltrexone.
- Opioid-containing medications (cough suppressants with codeine, antidiarrheals with loperamide at high doses): The analgesic and antitussive effects of opioid-containing products will be diminished or blocked entirely.
- Thioridazine: Concurrent use may cause increased lethargy and somnolence. Avoid combination when possible.
- Disulfiram: Both are used for alcohol dependence but concurrent use may increase hepatotoxicity risk. Monitor liver function if combined.
- Hepatotoxic medications (acetaminophen in high doses, certain statins): Naltrexone carries a boxed warning for hepatotoxicity at high doses; avoid combining with other hepatotoxic agents.
Additional Information
Naltrexone is an opioid antagonist used to treat alcohol use disorder and prevent relapse in opioid use disorder after detoxification. By blocking opioid receptors, it reduces the rewarding effects of alcohol and opioids, helping patients maintain abstinence.
Mechanism of Action
Naltrexone competitively binds to opioid receptors (primarily mu, with some kappa and delta activity):
- In opioid use disorder: Blocks the euphoric effects of opioids, reducing motivation to use
- In alcohol use disorder: Blocks endogenous opioid release triggered by alcohol, reducing the pleasurable effects and cravings
Unlike methadone or buprenorphine, naltrexone has no agonist activity and does not produce euphoria, physical dependence, or tolerance.
Available Formulations
- Oral tablets: 50 mg (daily dosing)
- Extended-release injectable suspension (Vivitrol): 380 mg IM every 4 weeks
The injectable form improves compliance by eliminating daily dosing decisions.
Medical Uses
FDA-Approved Indications:
- Alcohol use disorder (both formulations)
- Prevention of relapse to opioid dependence after opioid detoxification (both formulations)
Naltrexone is most effective as part of a comprehensive treatment program including counseling and psychosocial support.
Dosing Guidelines
Alcohol Use Disorder:
- Oral: 50 mg once daily
- IM: 380 mg every 4 weeks (gluteal injection, alternating sides)
Opioid Use Disorder:
- Oral: 50 mg once daily (or alternative regimens: 100 mg Monday/Wednesday, 150 mg Friday)
- IM: 380 mg every 4 weeks
Critical Requirement: Patient must be opioid-free for 7-10 days before starting naltrexone to avoid precipitated withdrawal. Urine drug screen and/or naloxone challenge recommended.
Important Safety Information
Black Box Warning (Injectable):
- Risk of hepatotoxicity
- Vulnerable to opioid overdose after discontinuation due to reduced tolerance
Contraindications:
- Current opioid use or dependence
- Acute opioid withdrawal
- Positive urine screen for opioids
- Acute hepatitis or liver failure
- Prior hypersensitivity to naltrexone
Warnings and Precautions:
- Hepatotoxicity: Monitor liver function
- Precipitation of opioid withdrawal if opioids present
- Patients should carry wallet card indicating naltrexone use
- Large opioid doses to overcome blockade can cause fatal overdose
- Depression and suicidality: Monitor closely
Drug Interactions
- Opioid analgesics: Blocked by naltrexone; higher doses needed for pain control (dangerous)
- Opioid-containing products: Avoid cough syrups, antidiarrheals with opioids
- Thioridazine: Increased lethargy and somnolence
Special Populations
- Hepatic Impairment: Use with caution; monitor liver function
- Renal Impairment: Use with caution in severe impairment
- Pregnancy: Use only if benefit outweighs risk
- Elderly: No specific adjustments but increased monitoring recommended
Overdose Management
Patients on naltrexone who require emergency analgesia present challenges:
- Higher opioid doses needed (with respiratory monitoring)
- Regional anesthesia, non-opioid analgesics, and general anesthesia preferred
- Consult pain management specialists
Frequently Asked Questions
Questions to Ask Your Doctor
Consider discussing these topics at your next appointment:
- ✓Should I carry a medical alert card indicating I am taking an opioid antagonist?
- ✓How will my pain be managed in an emergency if I need surgery while on naltrexone?
- ✓What liver function tests should be done before and during treatment?
- ✓Is the monthly Vivitrol injection a better option for me compared to daily oral tablets?
- ✓Are there behavioral therapy programs I should combine with naltrexone treatment?
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.
Related Medications
Other medications in the same category
Questions About This Medication?
Talk to your doctor or pharmacist about whether Naltrexone is right for you.
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