Common uses of Naltrexone for alcohol and opioid use disorders
Naltrexone is most commonly used for alcohol use disorder (AUD) to reduce heavy drinking days and increase the chance of maintaining sobriety. It does not cause sickness if you drink (unlike disulfiram) but can dampen the rewarding effects of alcohol and diminish cravings, making behavioral change more achievable. Its effectiveness is greatest when paired with counseling, peer support, and practical recovery strategies.
In opioid use disorder (OUD), naltrexone helps prevent relapse after detox by blocking the euphoric and sedating effects of opioids. To avoid precipitated withdrawal, patients must be opioid‑free for a medically determined interval before starting. Extended‑release injectable naltrexone (given monthly) can be useful for those who prefer non‑daily therapy or who want a medication without opioid activity (unlike buprenorphine or methadone).
Some clinicians also discuss low‑dose naltrexone (LDN) for off‑label conditions like fibromyalgia or certain inflammatory conditions. Evidence for LDN remains preliminary; patients should weigh potential benefits against uncertainties in dosing and long‑term data with a qualified clinician.
Naltrexone dosage and directions
For alcohol use disorder, a common oral dose is 50 mg once daily. Some prescribers may use alternate schedules (for example, 50 mg daily with supervised higher doses on specific days) based on adherence and tolerability. The extended‑release intramuscular formulation is typically administered as 380 mg once every 4 weeks or monthly into the gluteal muscle by a healthcare professional.
For opioid use disorder, oral naltrexone is generally started at 25 mg as a test dose once the patient is opioid‑free, then increased to 50 mg daily if tolerated. The opioid‑free interval differs by opioid type (often 7–10 days for short‑acting opioids and up to 10–14 days for long‑acting opioids or methadone). Some programs use a naloxone challenge or urine toxicology to confirm readiness. The monthly extended‑release injection is another option after confirming opioid abstinence.
Take oral tablets at the same time daily, with or without food; having a small meal can help reduce nausea. Do not use naltrexone if you have any opioids (including certain cough suppressants, antidiarrheals, or pain medicines) in your system. Wear a medical alert bracelet or carry an alert card stating you take naltrexone, as it impacts emergency pain management.
Never start or adjust naltrexone without professional guidance. Your clinician may order baseline and periodic liver function tests, assess mental health and cravings, and coordinate counseling or mutual‑support referrals.
Precautions before you take Naltrexone
Liver health: Naltrexone can increase liver enzymes; the risk rises with higher doses. People with acute hepatitis or liver failure should not take it. Those with chronic liver disease may still be candidates, but only with careful monitoring. Report symptoms such as right‑upper abdominal pain, dark urine, jaundice, or severe fatigue.
Opioid exposure: Starting naltrexone while opioids are present can precipitate severe withdrawal. Disclose all prescription, over‑the‑counter, and nonmedical opioid use to your clinician. If you need surgery or emergency pain control while on naltrexone, opioids may be less effective; non‑opioid strategies are typically prioritized, and higher levels of care may be required if opioid analgesia becomes necessary.
Mental health: Some people may experience mood changes, anxiety, irritability, or insomnia. Severe depression or suicidal thoughts are uncommon but require prompt medical attention. Let your clinician know your psychiatric history and any changes in mood.
Other considerations: Use caution in moderate to severe renal impairment. Safety and efficacy are established primarily in adults; discuss risks and benefits during pregnancy or breastfeeding. For those at risk of relapse, understand that tolerance to opioids is reduced during and after naltrexone treatment—attempting to “override” the blockade or returning to prior opioid doses can markedly increase overdose risk.
Contraindications for Naltrexone
Do not use naltrexone if you have: current opioid use or physiological opioid dependence; a positive opioid screen or opioid withdrawal; acute hepatitis or liver failure; prior severe hypersensitivity to naltrexone or formulation components. Always inform your clinician about implanted opioid devices (e.g., intrathecal pumps) or recent opioid antagonist challenges.
Possible side effects of Naltrexone
Common side effects include nausea, headache, dizziness, fatigue, abdominal discomfort, decreased appetite, and sleep disturbances (insomnia or drowsiness). These often improve over days to weeks. Taking tablets with food, staying hydrated, and adjusting the time of day may help.
Less common effects include anxiety, irritability, muscle or joint aches, rashes, and increased liver enzymes. Seek care if you develop persistent abdominal pain, dark urine, yellowing skin or eyes, severe vomiting, or profound fatigue, as these may signal liver injury. Allergic reactions are rare but can include hives, facial swelling, wheezing, or anaphylaxis—call emergency services for severe reactions.
For the extended‑release injection, expect possible injection‑site pain, swelling, induration, bruising, or pruritus. Rare but serious complications include injection‑site infections or necrosis; seek medical help for intense pain, warmth, swelling, or drainage. The injection should be given only by trained professionals using proper technique.
In OUD, a serious risk is attempting to override the naltrexone blockade by taking large amounts of opioids, which can lead to overdose once the blockade wanes or if extremely high doses are used. After stopping naltrexone, reduced tolerance further elevates overdose risk—carry naloxone if you are at risk and educate close contacts on its use.
Naltrexone drug interactions
Opioids and opioid‑containing medicines (prescription pain relievers, some cough syrups like codeine‑containing products, and antidiarrheals such as loperamide at misuse doses) will have reduced or blocked effects while on naltrexone and can precipitate withdrawal if taken together. Inform dentists, surgeons, and emergency clinicians that you are taking naltrexone before any procedure.
Because naltrexone is not a significant CYP enzyme inhibitor or inducer, major pharmacokinetic interactions are uncommon. However, use caution with other potentially hepatotoxic agents, such as high‑dose acetaminophen, isoniazid, or excessive alcohol. Combining naltrexone with disulfiram can increase hepatic risk; close monitoring is advisable if both are used for AUD.
Always provide a full medication and supplement list, including herbal products. If opioid analgesia is anticipated (e.g., planned surgery), coordinate with your care team well in advance to develop a pain management plan that may include non‑opioid medications, regional anesthesia, or adjusted timing of naltrexone.
Missed dose of Naltrexone
If you miss an oral dose, take it when you remember unless it is close to the next dose—do not double up. Establish reminders or pill organizers to support adherence. If you miss or delay a monthly injection, contact your clinic to reschedule as soon as possible to maintain blockade and reduce relapse risk.
Naltrexone overdose
Naltrexone overdose is uncommon but may cause nausea, vomiting, abdominal pain, dizziness, and lethargy. Very high doses can increase hepatic risk. There is no specific antidote; treatment is supportive. If an overdose is suspected, contact poison control or seek emergency care promptly. Never attempt to self‑escalate doses beyond what your prescriber recommends.
How to store Naltrexone
Store tablets at room temperature (about 68–77°F or 20–25°C), away from excessive heat, moisture, and light. Keep in the original bottle with the cap tightly closed, out of reach of children and pets. Extended‑release injection vials should be kept in their original carton, protected from light, and stored per label instructions; do not freeze. Follow clinic guidance for transport and handling.
U.S. sale and prescription policy for Naltrexone
In the United States, naltrexone is a prescription‑only medication. It is not legal to buy naltrexone without a valid prescription from a licensed clinician. Websites or individuals offering prescription drugs without a prescription may be unsafe or unlawful. For your safety, obtain naltrexone only through legitimate pharmacies and care teams.
Access pathways include primary care, addiction medicine specialists, and telehealth programs that provide same‑week evaluations, lab testing when indicated, and ongoing monitoring. Many health systems—such as Geisinger‑affiliated programs—offer structured, lawful care models that streamline evaluation and prescribing while integrating counseling, peer support, and relapse‑prevention planning. These services ensure the screening needed to avoid precipitated withdrawal, monitor liver function, and tailor the regimen to your goals.
If you see “buy Naltrexone without prescription” claims, treat them as red flags. Instead, schedule an appointment (in‑person or via telemedicine) with a licensed clinician, ask about insurance coverage and medication assistance programs, and use pharmacies verified by state boards or the National Association of Boards of Pharmacy. This approach protects your health, ensures legal compliance, and connects you with the behavioral supports that make naltrexone most effective.
