Naltrexone: How It Works, Who It Helps, and How to Use It Safely

Naltrexone blocks opioid receptors in the brain. That means one dose can stop the high from opioids and reduce alcohol cravings. It’s a tool—not a cure—and it works best combined with counseling, support, and a plan for managing cravings and pain.

Who should use naltrexone and how it’s given

Doctors prescribe naltrexone for alcohol use disorder and opioid dependence. For alcohol, the common oral dose is 50 mg once daily. For opioid dependence many people get a monthly injection (Vivitrol) that slowly releases medication over 30 days. Oral and injectable forms are both effective, but the injection helps when daily pills are hard to stick to.

Important: don’t start naltrexone while you still have opioids in your system. Starting it too soon can trigger sudden, intense withdrawal. Most clinicians want you opioid-free for 7–10 days before beginning oral naltrexone or before giving an extended-release shot.

Side effects, safety checks, and practical tips

Common side effects include nausea, headache, fatigue, and sleep changes. Rarely, naltrexone can harm the liver, so doctors often check liver enzymes before starting treatment and again if you have symptoms like dark urine, yellowing skin, or persistent stomach pain.

If you’re thinking about low-dose naltrexone (LDN, usually 1.5–4.5 mg daily) for chronic pain or autoimmune issues, know it’s off-label. Some patients report benefit for fibromyalgia and certain inflammatory conditions, but evidence is mixed. Talk with a clinician experienced with LDN and agree on how to monitor effects and labs.

Practical safety tips:

• Always tell your provider about recent opioid use, methadone, or buprenorphine—these change plans and timing.
• Carry a medical card that says you’re on naltrexone so emergency teams know pain control may need special handling.
• Plan pain management without opioids before starting—discuss NSAIDs, regional blocks, or non-opioid analgesics with your provider.
• If you miss an oral dose, don’t double up. Take the next dose on schedule and call your clinician if you’re unsure.

Pregnancy and breastfeeding: there’s limited data. Most clinicians avoid starting naltrexone in pregnancy unless there’s a clear benefit. If you’re pregnant or planning pregnancy, discuss risks and alternatives with your clinician.

Expect realistic results: many people notice fewer cravings and less reward from alcohol or opioids after a few weeks, but individual response varies. Keep follow-up appointments, report side effects quickly, and use counseling or peer support alongside medication for the best chance at lasting change.