Treatment & Safety
Naltrexone Contraindications: Opioids, Withdrawal, and Label Checks
Current opioid use, opioid dependence, acute withdrawal, specified test results, and prior hypersensitivity can make naltrexone unsafe to start.
Naltrexone: uses, safety and how to get treatment
An independent guide to naltrexone for alcohol and opioid use disorder. Compare tablets with the monthly injection, check when it is safe to start, and follow the prescription and funding routes in eight countries.
Independent and ad-free, with no sponsors or affiliate links. Peter Dunk writes the guides from medicine labels and national guidelines, and Dr Leonard Leng has medically reviewed our articles.
Key questions before starting naltrexone
Choose the question closest to yours. You do not need to read the site in order.
What does naltrexone do?
See how it blocks opioid receptors, why that can help with alcohol or opioid treatment, and what it does not do.
Is it safe to start now?
Recent opioid use is the first issue to raise. Even some pain, cough, and diarrhoea medicines can matter before the first dose.
Tablet or monthly injection?
Compare daily oral naltrexone with extended-release Vivitrol without treating them as interchangeable products.
How do I access treatment?
Country guides show the product, funding, and care routes we could verify—and the questions only a local service can answer.
Naltrexone prescriptions and access by country
A medicine can be clinically recognised yet difficult to find, unfunded, or available only in a different formulation. Pick your country for the practical route.
Four facts to know before taking naltrexone
These clear up many of the confusing or contradictory claims found online.
- Starting treatment. Naltrexone blocks opioid receptors. It does not treat acute withdrawal and can make withdrawal much worse if started too soon.
- Tablets and injection. Oral tablets and the extended-release injection share an active drug but differ in approved uses, administration, and access.
- Contrave formulation. Standalone naltrexone is a different product from Contrave, which also contains bupropion and is used for chronic weight management.
- Country-specific access. Price and supply need a country check. A registry listing alone cannot tell you what a nearby pharmacy has today.
Safety, side effects and starting treatment
Read about contraindications, the opioid-free interval before starting, side effects and Vivitrol injection administration.
Treatment & SafetyStarting Naltrexone After Opioids: Why the Opioid-Free Interval Matters
Naltrexone can trigger severe withdrawal if opioids are still present. The minimum interval is not a self-assessment rule and may be longer after buprenorphine or methadone.
Treatment & SafetyNaltrexone Side Effects: Expected Effects and Urgent Safety Signals
Nausea, headache, dizziness, and tiredness are reported with naltrexone. Vivitrol also has injection-site effects; certain symptoms need prompt clinical review.
Treatment & SafetyVivitrol Injection Administration: What Patients Should Know
Vivitrol is prepared and given only by a healthcare provider as a deep gluteal injection. This guide explains the patient-facing safety essentials.
Naltrexone access by country
Choose your country to see which product and care pathway are documented, then use the page’s questions when you speak with a clinician, pharmacist, or insurer.