Naltrexone: What to Know Before You Take It
Also known as Vivitrol, Revia
Other names: vivitrol, revia, low-dose-naltrexone, ldn
Naltrexone is an FDA-approved opioid receptor antagonist used for opioid use disorder and alcohol use disorder. At standard doses it blocks opioid receptors. At sub-therapeutic "low doses" (LDN, 1.5–4.5 mg) it is used off-label for chronic pain, fibromyalgia, Crohn's disease, and immune modulation — an area of active research.
In plain language
What Naltrexone is used for
- FDA-approved: opioid use disorder, alcohol use disorder
- Off-label/compounded: fibromyalgia, Crohn's disease, inflammatory conditions (active research)
Taking this medicine
How it is administered
- Oral tablet
- Oral capsule (compounded, low-dose)
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Risks and precautions
Risks and warnings
- Nausea, vomiting
- Loss of appetite
- Joint pain, muscle cramps
- Headache, dizziness, drowsiness
- Insomnia
Who should not take it
- Current opioid agonist use (precipitates acute withdrawal — serious risk)
- Acute hepatitis or liver failure
- Hypersensitivity to naltrexone
Medication review
Naltrexone drug interactions
FDA safety data
Most-reported side effects
Based on 39,971 FAERS reports. Reports do not prove the drug caused the effect.
Regulatory record
FDA recalls (7)
cGMP deviations: Temperature abuse
Recalling firm: Mckesson Medical-Surgical Inc. Corporate Office
Labeling: Not Elsewhere Classified. Drug product kit recalled due to 1 inch needles being placed in the 1 1/2 inch needle cardboard sleeve labelled as administration needles. The product vial is not impacted.
Recalling firm: Alkermes, Inc.
Labeling: Not Elsewhere Classified. Drug product kit recalled due to 1 inch needles being placed in the 1 1/2 inch needle cardboard sleeve labelled as administration needles. The product vial is not impacted.
Recalling firm: Alkermes Inc
Container packaging defect.
Recalling firm: Orexigen Therapeutics, Inc.
Defective Container: Customer complaints of punctures in the bottle.
Recalling firm: Orexigen Therapeutics, Inc.
Customer complaints for failure to deliver the dose.
Recalling firm: Alkermes, Inc.
Lack of Assurance of Sterility: Product did not meet the criteria for container closure integrity testing during routine 24 month stability testing.
Recalling firm: Alkermes, Inc.
Common questions
Patient questions
What is low-dose naltrexone (LDN) used for?
LDN (1.5–4.5 mg) is used off-label for chronic pain, fibromyalgia, Crohn's disease, and other inflammatory conditions. It is not FDA-approved for these uses. Evidence is emerging but not yet sufficient for FDA approval. It requires a prescription from a licensed provider and is typically dispensed as a compounded preparation.
Can I take naltrexone if I use opioids?
No. Naltrexone can precipitate severe opioid withdrawal in individuals physically dependent on opioids. You must be completely free of opioids (typically 7–10 days for short-acting opioids) before starting naltrexone. Your provider will confirm this before prescribing.
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This information is educational — not medical advice.
This page is provided for general educational purposes and summarizes publicly available data from sources such as the U.S. Food & Drug Administration. It is not a substitute for the judgment of a licensed clinician and should not be used to start, stop, or change any medication. It may be incomplete or out of date, and individual circumstances vary. Always talk with your prescriber or pharmacist about your specific medications and health conditions. If you think you may have a medical emergency, call 911.
Sources & References
- FDA structured product labeling for Naltrexone
- U.S. Food & Drug Administration — openFDA Drug Labeling API
- U.S. National Library of Medicine — RxNorm drug nomenclature
- FDA label: Vivitrol (naltrexone extended-release)
- NIH MedlinePlus: Naltrexone
Learn more about where our data comes from and how we write and review medical content.