Naltrexone
Naltrexone is an opioid receptor antagonist indicated for alcohol dependence and opioid dependence as part of a comprehensive treatment program. It blocks the euphoric and sedating effects of opioids and reduces alcohol cravings, making it a valuable tool in addiction treatment when combined with psychosocial support.
Clinical Overview
Primary Clinical Applications
Naltrexone is indicated for alcohol use disorder to reduce heavy drinking and maintain abstinence, and for opioid use disorder to prevent relapse after detoxification. It is available as oral tablets (Revia) and extended-release injection (Vivitrol) for improved compliance.
Mechanism and Clinical Benefits
As a competitive opioid receptor antagonist, naltrexone blocks the rewarding effects of alcohol and opioids. For alcohol dependence, it reduces craving and the reinforcing effects of drinking. For opioid dependence, it prevents euphoria and respiratory depression from opioid use.
Treatment Considerations
Patients must be opioid-free for 7-10 days before starting naltrexone to avoid precipitating withdrawal. The medication is most effective when combined with psychosocial interventions and requires ongoing monitoring and support for optimal outcomes.
Key Clinical Points
Seven to ten opioid-free days before starting
Starting naltrexone in a patient with opioids on board precipitates acute withdrawal. A negative urine screen, and a naloxone challenge where indicated, should confirm status first.
Loss of tolerance creates overdose risk
Patients who stop naltrexone and return to their previous opioid dose face substantially elevated overdose risk because tolerance has fallen. This warrants explicit counselling.
Monthly injection improves adherence
Vivitrol at 380 mg intramuscularly monthly removes the daily decision to take a medication that blocks reward, which is the central adherence problem with the oral form.
Blocks therapeutic opioid analgesia
Opioid analgesics will not work normally, which matters for planned surgery, trauma, and even over-the-counter antidiarrhoeals and cough preparations. Patients should carry documentation.
Contraindicated in acute hepatitis or liver failure
Liver function monitoring is required throughout. Combination with disulfiram carries additional hepatotoxicity risk with the oral formulation.
Prescribing Information
Dosing & Administration
Alcohol Dependence:
- Oral: 50 mg once daily
- Alternative: 100 mg every other day or 150 mg every 3 days
- Injectable (Vivitrol): 380 mg IM monthly
Opioid Dependence:
- Initial: 25 mg daily for 1-2 days (if no withdrawal)
- Maintenance: 50 mg daily
- Alternative: 100 mg every other day or 150 mg every 3 days
- Injectable (Vivitrol): 380 mg IM monthly
Pre-treatment Requirements:
- Opioid-free for 7-10 days minimum
- Negative urine drug screen
- Naloxone challenge test if indicated
Indications
- Alcohol dependence (as part of comprehensive treatment)
- Opioid dependence (prevention of relapse after detoxification)
Contraindications
- Current opioid use or physiological dependence
- Acute opioid withdrawal
- Positive urine screen for opioids
- Acute hepatitis or liver failure
- Hypersensitivity to naltrexone
Warnings & Precautions
- Hepatotoxicity: Monitor liver function tests
- Precipitated withdrawal: Ensure opioid-free status
- Increased opioid sensitivity: Risk of overdose if opioids used
- Depression and suicidality: Monitor mood, especially early treatment
- Injection site reactions: With Vivitrol injections
Drug Interactions
- Opioid analgesics: Blocks therapeutic effects
- Opioid-containing medications: Antidiarrheals, cough suppressants
- Disulfiram: Potential hepatotoxicity (oral naltrexone)
Adverse Reactions
Common:
- Nausea, headache, dizziness, fatigue, insomnia, anxiety
Injection Site (Vivitrol):
- Pain, tenderness, induration, swelling
Serious:
- Hepatotoxicity, depression, injection site necrosis
Special Populations
- Hepatic Impairment: Contraindicated in acute hepatitis or liver failure
- Renal Impairment: Use with caution, monitor closely
- Pregnancy: Category C – use only if benefits outweigh risks
- Emergency Medical Situations: Larger opioid doses may be needed
Frequently Asked Questions
What is Naltrexone used for?
Naltrexone is an opioid receptor antagonist indicated for alcohol dependence and opioid dependence as part of a comprehensive treatment program. It blocks the euphoric and sedating effects of opioids and reduces alcohol cravings, making it a valuable tool in addiction treatment when combined with psychosocial support.
What class of drug is Naltrexone?
Naltrexone is classified as: Opioid Antagonist.
Seven to ten opioid-free days before starting?
Starting naltrexone in a patient with opioids on board precipitates acute withdrawal. A negative urine screen, and a naloxone challenge where indicated, should confirm status first.
Loss of tolerance creates overdose risk?
Patients who stop naltrexone and return to their previous opioid dose face substantially elevated overdose risk because tolerance has fallen. This warrants explicit counselling.
Monthly injection improves adherence?
Vivitrol at 380 mg intramuscularly monthly removes the daily decision to take a medication that blocks reward, which is the central adherence problem with the oral form.
Blocks therapeutic opioid analgesia?
Opioid analgesics will not work normally, which matters for planned surgery, trauma, and even over-the-counter antidiarrhoeals and cough preparations. Patients should carry documentation.
Source: FDA prescribing information (DailyMed)