Drug class
Opioid receptor antagonist — blocks rather than activates brain receptors
Evidence reviewed
Medication guide
What is Naltrexone?
Naltrexone is an opioid-receptor antagonist used in treatment for alcohol dependence and to prevent relapse after opioid detoxification. Product approvals, formulations, and supply differ by country, so this hub separates universal medicine evidence from current local access records.
What naltrexone is and why it matters
Naltrexone is a prescription medication that blocks opioid receptors in the brain. Unlike replacement therapies such as methadone or buprenorphine, naltrexone does not activate these receptors — it simply prevents other substances from binding to them. This makes it non-addictive and particularly useful for people who have completed detoxification and want to maintain abstinence, or who want to reduce their drinking through targeted treatment.
It is available in most developed healthcare systems, though access, cost, and prescribing rules vary significantly by country. This guide covers the universal medical facts about naltrexone; the country pages explain how to get it where you live.
Key facts about naltrexone
Medically established facts you should know before considering treatment.
Primary uses
Alcohol dependence and opioid dependence are the two approved indications worldwide
Non-addictive
Naltrexone does not produce euphoria, does not create physical dependence, and has no withdrawal syndrome
Two forms
Daily oral tablets (50 mg) and monthly extended-release injection (380 mg). Not all forms are available in every country
Requires opioid abstinence
You must be opioid-free for 7–10 days before starting naltrexone to avoid precipitated withdrawal
Best with support
Clinical evidence shows naltrexone is most effective when combined with counselling, behavioural therapy, or structured recovery programmes
Development history
How naltrexone was developed
From laboratory discovery to worldwide regulatory approval.
1963
First synthesised
Naltrexone was first created at Endo Laboratories as researchers explored opioid antagonist compounds.
1984
FDA approval
The US Food and Drug Administration approved naltrexone for opioid dependence treatment.
1994
Alcohol dependence approved
The FDA extended approval to alcohol dependence after clinical trials demonstrated reduced relapse rates.
2006
Extended-release injection
A monthly injectable formulation was approved, removing the burden of daily pill adherence.
2000s–Present
Global adoption
Regulators worldwide including the TGA (Australia), Medsafe (New Zealand), HSA (Singapore), and MOHAP (UAE) have approved naltrexone.
Oral tablets vs. extended-release injection
| Oral naltrexone (commonly 50 mg) | Extended-release injection (380 mg) | |
|---|---|---|
| How taken | By mouth on the clinician's prescribed schedule | Deep gluteal injection every 4 weeks |
| Who administers | Usually self-administered | Healthcare professional only |
| Adherence trade-off | Flexible and lower acquisition cost in many markets, but doses can be missed | Avoids a daily tablet, but requires an appointment and injection-site monitoring |
| Product evidence | Current standalone products verified in several covered countries; not verified in UAE or Singapore | Vivitrol is FDA-approved in the US; current availability must be checked country by country |
| Price evidence | Use each dated country page; do not transfer a price between markets | Obtain a current provider and insurer quote |
Evidence at a glance
The direction of evidence is more useful than unsupported universal success percentages.
- Alcohol use disorder
- AUD
- Opioid use disorder
- OUD
- Established oral approach
- Daily
- Studied alternative
- Targeted
Oral and extended-release naltrexone can reduce return to heavy drinking in appropriately selected patients
Naltrexone is started only after an adequate opioid-free interval
The labelled and guideline-backed schedule in many health systems
Randomized trials exist, but the protocol is not standard or labelled everywhere
Core source
- US naltrexone tablet prescribing information (DailyMed)
Indications, contraindications, blockade, and safety warnings.
Common questions about naltrexone
How quickly does receptor blockade begin?
Oral naltrexone is absorbed after dosing, but the timing and clinical effect vary. Do not use a general onset estimate to plan opioid use or emergency pain care.
Does naltrexone prevent alcohol intoxication?
No. A person can still become impaired, lose coordination, make unsafe decisions, and develop alcohol poisoning. Naltrexone does not create the disulfiram reaction.
What side effects are common?
Nausea, headache, dizziness, fatigue, sleep disturbance, and other effects are described in product labels. Seek clinical assessment for severe symptoms or signs of acute hepatitis.
Is naltrexone addictive?
Naltrexone is an opioid antagonist and does not produce opioid euphoria or physical dependence. Its major safety issues include precipitated withdrawal if started too soon after opioids and increased overdose vulnerability around interrupted or stopped treatment.
How long is treatment?
There is no single duration for every indication or person. The clinician should define the intended outcome, review point, adherence plan, and stopping criteria.
Do I need a prescription?
Naltrexone is prescription-only in the countries covered here. Product registration and normal supply are not equally established in every market; use the dated country records.
Find naltrexone treatment where you live
Access, cost, and prescribing rules vary by country. Choose your location to learn how to get naltrexone through your local healthcare system.