Naltrexone: What It Does and How to Use It Safely

Naltrexone is a medicine that lowers cravings for alcohol and blocks the effects of opioids. Doctors prescribe it for alcohol use disorder and to help prevent opioid relapse. There are two main forms: a daily pill and a monthly injection. Both help people stay sober, but they work in slightly different ways and suit different situations.

How naltrexone works and who it's for

Naltrexone sits on opioid receptors in the brain without activating them. That stops opioids from producing a high and reduces the reward from drinking alcohol. People who want to stop drinking or avoid using opioids often do better with naltrexone plus counseling or support groups. It’s not a painkiller, so you can’t use it if you need opioid pain relief.

Dosing, safety checks, and practical tips

Typical oral dosing is 50 mg once daily. The injectable form (extended-release) is usually 380 mg once a month and is given in a clinic. Doctors may use lower or higher doses in special cases. Before starting, you usually need to be opioid-free for at least 7–10 days to avoid sudden withdrawal. If you were using long-acting opioids, your provider may wait longer or use tests to confirm no opioids are present.

Check liver tests first if you have liver disease or drink heavily; high doses can affect the liver. Common side effects include nausea, headache, fatigue, and sleep trouble. These often pass in a few days or weeks. Severe allergic reactions or unexplained liver pain are reasons to call your prescriber right away.

Low-dose naltrexone (LDN) is an off-label use where providers give much smaller daily doses (often 1.5–4.5 mg) for conditions like chronic pain or some autoimmune issues. Evidence for LDN is limited but growing. Talk with your clinician if you’re curious; don’t switch doses without medical advice.

Naltrexone blocks opioid pain relief, so if you need surgery or strong pain meds, tell your medical team. They may stop naltrexone temporarily. Also mention pregnancy or breastfeeding plans—naltrexone may not be appropriate during pregnancy and needs a specialist review.

Practical tips: set a routine for the daily pill, keep injection appointments if you use the monthly shot, and plan support like counseling. If you feel worse after starting or yearn for opioids, tell your provider—adjustments and extra support can help. Store medication out of reach of children and follow disposal rules for unused injections or pills.

Questions about cost, access, or local rules? RxCanadaPharm has guides on where to find prescriptions safely and how different pharmacies handle injectables and counseling referrals. Your prescriber or pharmacist can also explain coverage through provincial programs or private insurance.

If you want to start naltrexone, bring a list of current meds, recent opioid use, and any liver disease history to your appointment. Ask about follow-up timing and who to call for side effects. If cost is a concern, ask about provincial coverage, patient assistance programs, or generic pill options to lower out-of-pocket prices today.