Naltrexone dosage

Want clear, practical advice on how naltrexone is dosed? Naltrexone is used two main ways: full-dose to treat alcohol or opioid dependence, and low-dose (LDN) off-label for some autoimmune or pain conditions. The dose, timing, and safety checks are very different for each use — so knowing which path you’re on matters.

Common dosing regimens

Full-dose oral naltrexone (for alcohol use disorder or opioid relapse prevention): the usual starting and maintenance dose is 50 mg once daily by mouth. Some clinicians use 25 mg at first to check tolerance, then move to 50 mg. For people who prefer an injectable option, extended-release naltrexone (brand name Vivitrol) is given as a single 380 mg intramuscular injection once every 28–30 days.

Low-dose naltrexone (LDN) — off-label protocols vary, but common practice is 1.5 mg to 4.5 mg once daily, usually at bedtime. A typical titration is: start 1.5 mg nightly for 1–2 weeks, increase to 3 mg for 1–2 weeks, then move to 4.5 mg if needed. Some people start even lower (0.5–1 mg) and raise doses more slowly if they’re sensitive.

Important timing notes: for addiction treatment, patients must be opioid-free before starting. Clinicians often require 7–14 days without short-acting opioids (longer if using methadone) and may perform a naloxone or monitored challenge to avoid precipitating withdrawal. For Vivitrol, a similar opioid-free window and negative opioid test are required before injection.

Safety, interactions & monitoring

Check liver tests before starting and during treatment if you’re on high doses or have liver disease. Naltrexone can raise liver enzymes, especially at higher doses. It’s not used in acute hepatitis or liver failure. Pregnancy and breastfeeding: data are limited, so discuss risks with your doctor.

Biggest drug interaction: opioids. Naltrexone blocks opioid receptors, so it will stop opioid painkillers from working and can cause sudden withdrawal in someone recently using opioids. Tell your surgeon and pain team if you take naltrexone — you may need a special plan for anesthesia or pain control.

Common side effects include nausea, headache, fatigue, sleep changes, and vivid dreams. Low-dose regimens often have fewer or milder side effects. If you develop persistent abdominal pain, jaundice, or extreme fatigue, stop the drug and contact your provider.

Missed dose guidance: if you miss a day, take the next scheduled dose — don’t double up. If you plan to start opioids after taking naltrexone, talk to your clinician: they’ll advise on washout timing and testing.

Bottom line: follow a prescribing clinician’s plan, get baseline liver tests, confirm you’re opioid-free before full-dose or injectable starts, and use cautious titration for LDN. If you’re unsure what dose fits your situation, ask your healthcare provider for a personalized plan.