Naltrexone: A Cornerstone in Opioid and Alcohol Use Management
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Naltrexone is a potent opioid antagonist medication that represents a critical advancement in the management of substance use disorders. It functions by competitively binding to opioid receptors in the brain, effectively blocking the euphoric and sedative effects of opioids and reducing the rewarding effects of alcohol. This pharmacological profile makes it an indispensable tool in relapse prevention, supporting long-term recovery goals. Its use is grounded in extensive clinical research and is a key component of comprehensive, evidence-based treatment plans under medical supervision.
Features
- Pharmacological Class: Pure opioid antagonist.
- Available Formulations: Oral tablets (50 mg standard) and extended-release intramuscular injectable suspension (380 mg/vial).
- Mechanism of Action: Competitive binding at mu-opioid receptors.
- Bioavailability: Oral formulation has 5–40% bioavailability due to significant first-pass metabolism.
- Half-Life: Oral naltrexone has a half-life of approximately 4 hours; its active metabolite, 6-β-naltrexol, has a half-life of 13 hours. The injectable form provides sustained release over approximately 30 days.
- Metabolism: Primarily hepatic, via dihydrodiol dehydrogenase.
- Excretion: Primarily renal.
Benefits
- Effective Relapse Prevention: Significantly reduces the risk of relapse to opioid use by blocking the desired effects, thereby removing the pharmacological incentive for use.
- Reduces Alcohol Cravings: Helps decrease the frequency and intensity of alcohol cravings, supporting abstinence in alcohol use disorder.
- Non-Addictive and Non-Narcotic: As an antagonist, it does not produce euphoria, dependence, or tolerance, eliminating the risk of misuse.
- Supports Psychosocial Therapies: By managing the biological drivers of addiction, it allows patients to more fully engage in and benefit from counseling and behavioral therapies.
- Flexible Administration Options: The availability of both daily oral and monthly injectable formulations allows for personalized treatment plans that support adherence.
Common use
Naltrexone is FDA-approved for the treatment of:
- Opioid Use Disorder (OUD): For the prevention of relapse in patients who have undergone complete opioid detoxification.
- Alcohol Use Disorder (AUD): For the maintenance of abstinence from alcohol in patients who have achieved initial abstinence.
It is also used off-label in certain cases for other impulse-control disorders, though this application requires careful specialist evaluation.
Dosage and direction
Crucial Prerequisite: Initiation of naltrexone therapy requires a complete absence of opioids from the patient’s system. A naloxone challenge test is often recommended to confirm this, as precipitating withdrawal is a significant risk.
Oral Tablets (e.g., Revia®):
- Initial Dose for OUD/AUD: 25 mg once daily to assess tolerability.
- Maintenance Dose: 50 mg once daily.
- Alternative Dosing: Some protocols use 100 mg every other day or 150 mg every third day to improve adherence, though daily dosing is standard.
- Administration: Can be taken with or without food to minimize gastrointestinal upset.
Extended-Release Injection (Vivitrol®):
- Dose: 380 mg delivered via intramuscular (IM) gluteal injection by a healthcare professional every 4 weeks (monthly).
- Administration: The suspension must be prepared and administered precisely according to the manufacturer’s instructions.
Precautions
- Precipitated Withdrawal: The most serious risk upon initiation. Patients must be opioid-free for a minimum of 7-10 days. Self-reporting is not sufficient; use urine toxicology and clinical assessment.
- Hepatotoxicity: Dose-related hepatocellular injury is possible. Liver function tests (LFTs) are recommended before initiation and periodically during therapy, especially at higher doses.
- Depression and Suicidality: Monitor patients for the emergence or worsening of depression, suicidal ideation, or unusual changes in behavior.
- Opioid Tolerance Loss: Patients will have a reduced tolerance to opioids. If they relapse and use their previous dose of opioids, they are at a drastically increased risk of fatal overdose.
- Pneumonia: An increased incidence of pneumonia has been observed in patients treated with naltrexone; monitor for signs and symptoms.
Contraindications
- Current physical dependence on opioids or acute opioid withdrawal.
- Positive urine screen for opioids.
- Acute hepatitis or liver failure.
- History of hypersensitivity to naltrexone or any component of the formulation (e.g., polylactide-co-glycolide microspheres in the injectable).
Possible side effect
Common side effects are often transient and may include:
- Nausea, vomiting, abdominal pain, diarrhea
- Headache, dizziness, nervousness
- Insomnia, anxiety
- Fatigue, drowsiness
- Muscle or joint aches
- Injection site reactions (for Vivitrol®): pain, tenderness, induration, swelling, erythema, bruising, pruritus.
Less common but more serious side effects require medical attention:
- Signs of hepatitis (e.g., dark urine, jaundice, right upper quadrant pain)
- Severe depression or suicidal thoughts
- Respiratory depression (if opioids are used to overcome the blockade)
- Eosinophilic pneumonia
Drug interaction
- Opioid Analgesics: Naltrexone will block the therapeutic effects of opioid pain medications, including those used for surgical analgesia, trauma, or acute dental pain. Non-opioid analgesic strategies must be planned for.
- Opioid-Containing Medications: Will also block the effects of opioid antitussives (e.g., codeine) and antidiarrheals (e.g., diphenoxylate/atropine).
- Thioridazine: Concurrent use may cause pronounced drowsiness and lethargy.
- Hepatotoxic Drugs: Caution is advised when co-administering with other medications known to cause hepatic injury (e.g., certain anticonvulsants, antipsychotics).
Missed dose
- Oral Tablets: If a daily dose is missed, it should be taken as soon as remembered. If it is close to the time of the next dose, the missed dose should be skipped. Do not double the dose to make up for a missed one.
- Injectable (Vivitrol®): Schedule the next injection as soon as possible. Consistent monthly dosing is critical for maintaining the opioid blockade.
Overdose
Naltrexone alone in massive overdose has not been associated with serious injury or death. There is no known specific antidote. Management involves discontinuation of the drug and institution of supportive measures. However, a patient who has overdosed on naltrexone may be attempting to overcome the blockade with opioids, which places them at extreme risk of a concurrent, life-threatening opioid overdose that requires immediate administration of naloxone and emergency medical care.
Storage
- Oral Tablets: Store at room temperature (20°–25°C or 68°–77°F) in a tight, light-resistant container. Keep out of reach of children.
- Injectable (Vivitrol®): The kit must be refrigerated (2°–8°C or 36°–46°F). Do not freeze. The prepared suspension must be administered immediately after mixing.
Disclaimer
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or medication. Never disregard professional medical advice or delay in seeking it because of something you have read here.
Reviews
- “As an addiction psychiatrist, naltrexone is a first-line agent in my toolkit for motivated patients. The injectable formulation, in particular, solves the adherence issues we often see in early recovery, providing a stable ‘safety net’ for patients as they rebuild their lives.” – Dr. A., MD, Psychiatry
- “The science behind naltrexone is robust. Its ability to disrupt the reward pathway pharmacologically gives patients a fighting chance to break the cycle of addiction. It’s not a magic bullet, but it’s one of the most powerful tools we have when combined with therapy.” – Clinical Pharmacologist
- “Implementing naltrexone therapy requires a meticulous protocol to avoid precipitated withdrawal. However, for the appropriate patient who is fully detoxified, it can be truly life-changing and is a cornerstone of medication-assisted treatment.” – Addiction Medicine Specialist