What is naltrexone?
Naltrexone is a prescription medicine that blocks opioid receptors. It is used in treatment for alcohol use disorder and, after opioid withdrawal, opioid use disorder. It is not an opioid, a detox medicine, or an overdose treatment.
The short version
Naltrexone sits on opioid receptors without activating them. For alcohol use disorder, that can reduce some of alcohol’s rewarding pull and lower heavy-drinking outcomes for some people. For opioid use disorder, it can block opioid effects after a person has completed withdrawal.
The timing matters. Starting naltrexone while opioids are still present can trigger sudden, severe withdrawal. It also changes overdose risk during and after treatment. That is why the first useful conversation is not simply ‘Can I get a prescription?’ but ‘Is naltrexone suitable, and is it safe for me to start now?’
What it does—and what it does not do
These distinctions prevent many of the most dangerous misunderstandings.
- Blocks; it does not replace opioids. Naltrexone is different from methadone and buprenorphine. It does not activate opioid receptors or prevent opioid withdrawal symptoms.
- Can support alcohol treatment. It may reduce heavy drinking or help prevent return to drinking for some people. It does not stop intoxication, impaired judgement, or alcohol poisoning.
- Requires an opioid-free interval. Recent opioid exposure—including some pain, cough, and diarrhoea medicines—needs to be reviewed before the first dose or injection.
- Works best as part of care. A medicine can support a goal, but it does not replace follow-up, behavioural support, overdose planning, or treatment of other health needs.
Naltrexone for alcohol use disorder
- Licensed use. The US label indicates oral naltrexone “in the treatment of alcohol dependence”. It is one part of a treatment plan, not a cure on its own.
- What guidelines advise. In England, NICE advises considering acamprosate or oral naltrexone, together with an individual psychological intervention, after a successful withdrawal for people with moderate or severe alcohol dependence. It can also be considered for harmful drinking or mild dependence when psychological treatment alone has not helped, or when the person asks for medication. NICE advises a medical assessment with liver tests before starting.
- What the evidence shows. A Cochrane review of 50 randomised trials with 7,793 people found that naltrexone lowered the risk of heavy drinking to 83% of the placebo group’s risk and reduced drinking days by about 4%. Its effect on any return to drinking did not reach statistical significance. Nausea and daytime sleepiness were the main side effects. The average benefit is moderate and varies from person to person.
- Daily or targeted. The labelled approach is a daily dose. Taking it only before planned drinking is a different approach with its own evidence: see targeted naltrexone.
- Before the first dose. Naltrexone does not treat alcohol withdrawal, and recent opioid use has to be ruled out first: see starting naltrexone safely.
Oral naltrexone and extended-release Vivitrol are not interchangeable
| Oral naltrexone | Extended-release Vivitrol | |
|---|---|---|
| Form | Commonly a 50 mg tablet | 380 mg suspension for injection |
| Routine | Taken on the schedule set by the prescriber | Given every four weeks or once monthly under the US label |
| Who gives it | Usually taken by the patient | Healthcare professional only |
| Practical trade-off | No injection appointment, but each scheduled dose can be missed | No daily tablet, but requires a visit and injection-site monitoring |
| Availability | Verified in several—not all—countries covered here | Strongest current access evidence on this site is from the United States |
Useful orientation
The exact label and treatment plan still depend on the product and country.
- Alcohol use disorder: AUD. Oral and extended-release forms are used in treatment, depending on jurisdiction.
- Opioid use disorder: OUD. Treatment begins only after an adequate opioid-free interval.
- Common oral tablet strength: 50 mg. A product strength, not a personal dosing recommendation.
- US Vivitrol presentation: 380 mg. A healthcare-provider-administered monthly injection.
Questions people often ask
Is naltrexone addictive?
Naltrexone does not produce opioid euphoria or physical dependence. Its important risks are different: precipitated withdrawal if it is started too soon, attempts to overcome the blockade, and overdose vulnerability after missed or stopped treatment.
Will I still feel alcohol?
Yes. Naltrexone does not prevent intoxication, poor coordination, impaired decisions, sedation, or alcohol poisoning. Some people experience less reward or craving; response varies.
Can I take opioid pain relief while using it?
Opioid pain medicines may work poorly or differently, and trying to override the blockade is dangerous. Tell every treating professional that you use naltrexone, especially before surgery, dental work, or emergency pain care.
What about the liver?
Current labels include hepatitis and liver-dysfunction warnings. A clinician can interpret symptoms, history, other medicines, alcohol exposure, and tests together; a single web rule cannot decide suitability.
Is Contrave the same treatment?
No. Contrave combines naltrexone with bupropion for chronic weight management. It has a different dose, indication, label, and safety profile.
How long does treatment last?
There is no duration that fits everyone. A useful plan names the goal, follow-up date, adherence support, safety plan, and what would prompt a change.
Turn the overview into a useful conversation
Next, check the safety guide and your country page. Take the exact product name and a complete medication list to the appointment.
Sources
Checked .
- Current US oral naltrexone prescribing information (DailyMed). Indications, contraindications, opioid blockade, and safety warnings.
- SAMHSA: medication for alcohol use disorder. Clinical guide covering oral and extended-release naltrexone alongside other alcohol-treatment medicines.
- NICE CG115: alcohol-use disorders, recommendations on medication after withdrawal — National Institute for Health and Care Excellence. Acamprosate or oral naltrexone with psychological intervention; assessment before starting. Checked 22 October 2026.
- Opioid antagonists for alcohol dependence (Rösner et al., Cochrane review, 2010) — Cochrane Database of Systematic Reviews. 50 randomised trials, 7,793 people; heavy-drinking risk ratio 0.83. Checked 22 October 2026.