Naltrexone: what it does, how to use it, and key safety tips

Here’s a sharp fact: naltrexone can block the pleasurable effects of alcohol and opioids. That makes it a powerful tool for cutting cravings and preventing relapse. It’s not a cure, but for many people it’s a useful part of recovery or symptom control.

How naltrexone works

Naltrexone is an opioid antagonist. That means it sticks to opioid receptors in the brain and prevents opioids from producing their usual effects. For alcohol, it reduces the rewarding buzz that drives repeated drinking. You’ll see naltrexone used two main ways: daily oral tablets (usually 50 mg) and a monthly extended-release injection (Vivitrol, 380 mg). There’s also “low-dose naltrexone” (LDN, typically 1.5–4.5 mg) used off-label for pain and some autoimmune conditions, but that’s a different strategy and still under study.

Practical dosing and starting points

Oral naltrexone commonly starts at 50 mg once per day. The monthly injection is given by a clinic and can help people who prefer not to take a daily pill. If someone uses opioids, they must stop first. For oral naltrexone the usual recommendation is 7–10 days opioid-free; for the injection you often need a longer opioid-free period and a negative urine opioid test. This prevents severe, immediate withdrawal.

Low-dose naltrexone is a separate practice. People try it for chronic pain, fibromyalgia, and some autoimmune issues at much smaller doses. Evidence is mixed and dosing varies, so talk to a clinician experienced with LDN before trying it.

Before starting naltrexone, clinicians usually check liver function tests (LFTs). Naltrexone can affect the liver, especially at higher doses or with heavy alcohol use. If LFTs are very high, treatment may be delayed or avoided.

Safety, side effects, and what to check before you start

Common side effects include nausea, headache, insomnia, and fatigue. Most side effects fade after a few days to weeks. Serious liver injury is rare but possible, so baseline LFTs and periodic checks are standard. Never take naltrexone if you’re currently using opioids or are in acute opioid withdrawal — it will trigger severe withdrawal.

If you’re pregnant or breastfeeding, talk to your provider. Some people tolerate naltrexone well; others don’t. If you plan surgery or expect to need opioids for pain, tell your surgical team — naltrexone changes how pain meds work and may require special planning.

Access and timing: naltrexone needs a prescription. The injection is given in a clinic, which helps with adherence but costs more and may need prior authorization from insurers. Oral tablets are easy to fill but rely on daily use.

Bottom line: naltrexone is a practical, evidence-based option for alcohol and opioid dependence and shows promise in other areas. Talk to a clinician about your goals, test results (especially liver tests), and any current opioid use before starting. That keeps treatment safe and more likely to help.