Naltrexone: uses, dosing, side effects & brands
Naltrexone is an opioid antagonist sold in the U.S. under 2 brand and generic names, for alcoholism, opioid-related disorders and drug overdose. Below: what the FDA label says, every product that contains it, what the pills look like, and its recall record.
Key facts
- Drug class
- Opioid Antagonist
- Treats
- Alcoholism, Opioid-Related Disorders and Drug Overdose
- Available as
- Kit
- Sold as
- 2 products — Vivitrol and Naltrexone
- Prescription?
- Prescription only
- Generic available?
- Yes
- What the pharmacy pays
- about $36 for a 30-count supply — not your price
How naltrexone is dosed
From the FDA label for Vivitrol (application NDA021897). Other naltrexone products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.
Naltrexone for extended-release injectable suspension must be prepared and administered by a healthcare provider (2.1 , 2.6) . Prior to initiating naltrexone for extended-release injectable suspension, an opioid-free duration of a minimum of 7–10 days is recommended for patients, to avoid precipitation of opioid withdrawal that may be severe enough to require hospitalization (2.1) . The recommended dose of naltrexone for extended-release injectable suspension is 380 mg delivered intramuscularly (deep) as a gluteal injection, every 4 weeks or once a month, alternating buttocks for each subsequent injection, using the carton components provided (2.1) . Naltrexone for extended-release injectable suspension must ONLY be administered as a deep intramuscular gluteal injection ( 2.1 ) . See Full Prescribing Information for complete Directions for Use (2.6) . 2.1 Important Dosage and Administration Information Naltrexone for extended-release injectable suspension must be prepared and administered by a healthcare provider. Naltrexone for extended-release injectable suspension must ONLY be administered as a deep intramuscular gluteal injection. Parenteral products should be visually inspected for particulate matter and discoloration prior to administration whenever solution and container permit. A properly mixed suspension will be milky white, will not contain clumps, and will move…
Naltrexone side effects
The following clinically significant adverse reactions are described elsewhere in the labeling: Accidental Opioid Overdose [see Warnings and Precautions ( 5.1 ) ] Injection Site Reactions [see Warnings and Precautions ( 5.2 ) ] Precipitated Opioid Withdrawal [see Warnings and Precautions ( 5.3 ) ] Hepatotoxicity [see Warnings and Precautions ( 5.4 ) ] Depression and Suicidality [see Warnings and Precautions ( 5.5 ) ] Eosinophilic Pneumonia [see Warnings and Precautions ( 5.7 ) ] Hypersensitivity Reactions [see Warnings and Precautions ( 5.8 ) ] The adverse events seen most frequently in association with naltrexone for extended-release injectable suspension therapy for alcohol dependence (i.e., those occurring in ≥5% and at least twice as frequently with naltrexone for extended-release injectable suspension than placebo) include nausea, vomiting, injection site reactions (including induration, pruritus, nodules and swelling), muscle cramps, dizziness or syncope, somnolence or sedation, anorexia, decreased appetite or other appetite disorders (6) . The adverse events seen most frequently in association with naltrexone for extended-release injectable suspension therapy in opioid-dependent patients (i.e., those occurring in ≥2% of patients treated with naltrexone for extended-release injectable suspension and at least twice as frequently with naltrexone for extended-release…
Who shouldn’t take naltrexone
Naltrexone for extended-release injectable suspension is contraindicated in: Patients receiving opioid analgesics [see Warnings and Precautions ( 5.3 ) ] . Patients with current physiologic opioid dependence [see Warnings and Precautions ( 5.3 ) ] . Patients in acute opioid withdrawal [see Warnings and Precautions ( 5.3 ) ] . Any individual who has failed the naloxone challenge test or has a positive urine screen for opioids [see Warnings and Precautions ( 5.3 ) ] . Patients who have previously exhibited hypersensitivity to naltrexone, PLG, carboxymethylcellulose, or any other components of the diluent [see Warnings and Precautions ( 5.8 ) ]. Naltrexone for extended-release injectable suspension is contraindicated in: Patients receiving opioid analgesics (4) . Patients with current physiologic opioid dependence (4) . Patients in acute opioid withdrawal (4) . Any individual who has failed the naloxone challenge test or has a positive urine screen for opioids (4) . Patients who have previously exhibited hypersensitivity to naltrexone, polylactide-co-glycolide (PLG), carboxymethylcellulose, or any other components of the diluent (4) .
Naltrexone drug interactions
Patients taking naltrexone for extended-release injectable suspension may not benefit from opioid-containing medicines. Naltrexone antagonizes the effects of opioid-containing medicines, such as cough and cold remedies, antidiarrheal preparations and opioid analgesics. Naltrexone antagonizes the effects of opioid-containing medicines, such as cough and cold remedies, antidiarrheal preparations, and opioid analgesics (7) .
Every naltrexone product we track (2)
Same active ingredient — different manufacturer, form, price and FDA recall record. That last one is what our independent score measures.
| # | Drug | Rating | Type | Form | Generic? | Pharmacy pays | |
|---|---|---|---|---|---|---|---|
| 1 | 70/100 | Prescription | Kit | Generic | $36 | View → | |
| 2 | 56/100 | Prescription | Kit | Generic | $36 | View → |
What naltrexone pills look like
Imprint codes, colour and shape from the FDA’s labelling data. Match the imprint on your pill — or search any imprint.
Combination products containing naltrexone
A combination is a different drug — different dosing, different warnings. It is listed here so you can find it, not so you can substitute it.
Naltrexone and breastfeeding
From LactMed, the US National Library of Medicine’s Drugs and Lactation Database — quoted, not rewritten.
Full LactMed record for naltrexone: levels in milk, effects in breastfed infants, and the drugs it would consider insteadLimited data indicate that naltrexone is minimally excreted into breastmilk. If the mother requires naltrexone, it is not a reason to discontinue breastfeeding.
National Institute of Child Health and Human Development, record revised February 15, 2026. LactMed states its information is not a substitute for professional judgement.
What people report to the FDA about naltrexone
The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 8,874 reports naming naltrexone, and the FDA flagged 62% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:
- nausea739 reports
- fatigue734 reports
- headache520 reports
- dizziness393 reports
- vomiting390 reports
- insomnia375 reports
- diarrhoea373 reports
- anxiety367 reports
Read these as a signal, not a rate. A report does not mean naltrexone caused the effect — anyone can file one, and many describe people taking several medicines for several conditions. Crucially there is no denominator: FAERS does not record how many people took the drug, so these counts cannot be turned into “X% of patients” — a bigger number often just means a more widely used or more talked-about drug. Duplicates exist, and publicity drives reporting. For what is actually established, read the FDA label section above.
Source: openFDA drug/event (FAERS), retrieved July 25, 2026.
Related calculators
Frequently asked questions
What is naltrexone?
Naltrexone for extended-release injectable suspension is supplied as a microsphere formulation of naltrexone for suspension, to be administered by deep intramuscular injection by a healthcare practitioner. Naltrexone for extended-release injectable suspension contains naltrexone base anhydrous as the active pharmaceutical ingredient. Naltrexone is an opioid antagonist with little, if any, opioid agonist activity. Naltrexone is morphinan-6-one, 17-(cyclopropylmethyl)-4,5-epoxy-3,14-dihydroxy-(5α) (CAS Registry # 16590-41-3).
What kind of drug is naltrexone?
The FDA classifies naltrexone as an opioid antagonist. Opioid antagonists attach to the same brain and body receptors that opioids use, but without switching them on. By occupying those receptors, they block opioids from binding and can rapidly reverse an overdose or curb opioid cravings. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.
Can you take naltrexone with other medicines?
It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run naltrexone against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.
What brand names is naltrexone sold under?
We track 2 naltrexone-containing products in the U.S.: Vivitrol and Naltrexone. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.
What forms does naltrexone come in?
Across the brands we track, naltrexone is currently marketed as kit, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.
Is there a generic naltrexone?
Yes. Our catalog lists 1 generic naltrexone product alongside the brand versions. A generic has the same active ingredient and must meet the FDA's bioequivalence standard; it usually costs less. Ask your pharmacist which one your plan covers.
What is naltrexone used for?
Naltrexone is FDA-approved to treat alcohol use disorder and opioid use disorder. It is an opioid blocker that reduces cravings and blunts the rewarding effects of alcohol and opioids, helping people stay in recovery. It comes as a daily tablet and as a once-monthly injection (brand Vivitrol). It is used as part of a broader treatment program, not as a standalone cure.
What is low-dose naltrexone (LDN) used for?
Low-dose naltrexone — typically around 1.5 to 4.5 mg, far below the approved 50 mg dose — is prescribed off-label for chronic pain conditions like fibromyalgia, and for some autoimmune and inflammatory conditions. This is not an FDA-approved use, the evidence is still limited and debated, and it should only be used under a doctor's supervision.
Why can't you take naltrexone while using opioids?
Because naltrexone blocks opioid receptors, taking it while opioids are in your system can trigger sudden, severe opioid withdrawal. People generally must be opioid-free for 7 to 10 days before starting it. It also means opioid pain medicines won't work normally, which matters in an emergency — so carry medical information noting you take it.
Cite this page
- APA
- pharmaranks. (2026, July 24). Naltrexone: uses, dosing, side effects & brands. https://pharmaranks.com/drugs/naltrexone
- MLA
- “Naltrexone: uses, dosing, side effects & brands.” pharmaranks, 24 July 2026, https://pharmaranks.com/drugs/naltrexone.
We summarise public FDA and NIH sources — for a clinical claim, cite the primary source we link to as well.
Sources: FDA openFDA drug label, National Drug Code Directory, and Enforcement (recall) database. This page reproduces public FDA data and is not medical advice. Dosing is set by your prescriber.
Read the full FDA label for naltrexone on DailyMed (NIH) ↗.