Nalmefene: uses, dosing, side effects & brands
Nalmefene is an opioid antagonist sold in the U.S. under 2 brand and generic names, for opioid-related disorders, respiration 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 (across its forms)
- Opioid-Related Disorders, Respiration Disorders and Drug Overdose
- Available as
- Spray/Inhaler · Injectable
- Sold as
- 2 products — Opvee and Zurnai (Autoinjector)
- Prescription?
- Prescription only
- Generic available?
- Not in our catalog
How Opvee is dosed
From the FDA label for Opvee (application NDA217470). Other nalmefene products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.
OPVEE nasal spray is for intranasal use only ( 2.1 ) Seek emergency care immediately after use ( 2.1 ) Administer a single spray of OPVEE nasal spray intranasally into nose. ( 2.2 ) Administer additional doses of OPVEE nasal spray, using a new nasal spray with each dose, if the patient does not respond or responds and then relapses into respiratory depression, additional doses of OPVEE nasal spray may be given every 2 to 5 minutes until emergency medical assistance arrives. ( 2.2 ) Additional supportive and/or resuscitative measures may be helpful while awaiting emergency medical assistance. ( 2.2 ) 2.1 Important Administration Instructions OPVEE is for intranasal use only. The device is ready to use. No device assembly is required. Do not prime or test prior to administration. OPVEE nasal spray delivers its entire contents automatically, upon activation. Do not attempt to reuse OPVEE. Each unit-dose device contains a single dose of nalmefene and cannot be reused. No device assembly is required. Because treatment of suspected opioid overdose must be performed by someone other than the patient, instruct the prescription recipient to inform those around them about the presence of OPVEE nasal spray and the Instructions for Use . Instruct the patient or caregiver to read the Instructions for Use at the time they receive a prescription for OPVEE nasal spray. Emphasize the following…
Everything below is the FDA label for Opvee (spray/inhaler). Nalmefene is also sold as injectable, and those are different medicines to take — follow the label for the one you were prescribed.
Opvee side effects
The following serious adverse reactions are discussed elsewhere in the labeling: Recurrent Respiratory and Central Nervous System Depression [see Warnings and Precautions (5.1) ] Precipitation of Severe Opioid Withdrawal [see Warnings and Precautions (5.3) ] Most common adverse reactions (incidence at least 2%) are nasal discomfort, headache, nausea, dizziness, hot flush, vomiting, anxiety, fatigue, nasal congestion, throat irritation, rhinalgia, decreased appetite, dysgeusia, erythema, and hyperhidrosis. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Indivior Inc. at 1-877-782-6966 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to the rates in clinical trials of another drug and may not reflect the rates observed in practice. The safety of OPVEE nasal spray is supported by safety and pharmacokinetic studies of OPVEE nasal spray in healthy subjects in a normal state and under steady state opioid agonism. The following adverse reactions were observed. In a pharmacokinetic study of 66 healthy adult volunteers exposed to one spray of OPVEE nasal spray in one nostril the most common adverse reactions were: nasal discomfort and dizziness. In a second pharmacokinetic study of 24…
Who shouldn’t take Opvee
OPVEE nasal spray is contraindicated in patients known to be hypersensitive to nalmefene or to any of the other ingredients. Hypersensitivity to nalmefene or to any of the other ingredients. ( 4 )
Every nalmefene 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 | Not yet rated | Prescription | Spray/Inhaler | No data | — | View → | |
| 2 | Not yet rated | Prescription | Injectable | No data | — | View → |
How long nalmefene keeps
No nalmefene label we read sets a separate limit for after opening, but they do specify how it must be stored — and the stability behind any date assumes those conditions.
Does nalmefene expire? The in-use limits and storage rules from its labelsWhat people report to the FDA about nalmefene
The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 99 reports naming nalmefene, and the FDA flagged 97% 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:
- coma24 reports
- agitation8 reports
- febrile bone marrow aplasia7 reports
- muscle spasms7 reports
- septic shock7 reports
- electrocardiogram qt prolonged6 reports
- alcohol poisoning5 reports
- bradycardia5 reports
Read these as a signal, not a rate. A report does not mean nalmefene 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 Opvee?
Opvee (Nalmefene Hydrochloride) is an opioid antagonist used to treat Opioid-Related Disorders, Respiration Disorders, Drug Overdose.
What kind of drug is nalmefene?
The FDA classifies nalmefene 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 nalmefene 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 nalmefene 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 nalmefene sold under?
We track 2 nalmefene-containing products in the U.S.: Opvee and Zurnai (Autoinjector). They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.
What forms does nalmefene come in?
Across the brands we track, nalmefene is currently marketed as spray/inhaler and injectable, 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 nalmefene?
We do not currently list a generic-labelled nalmefene product. That does not always mean none exists — it means none appears under a generic name in the FDA data we track. Ask your pharmacist.
Cite this page
- APA
- pharmaranks. (2026, July 24). Nalmefene: uses, dosing, side effects & brands. https://pharmaranks.com/drugs/nalmefene
- MLA
- “Nalmefene: uses, dosing, side effects & brands.” pharmaranks, 24 July 2026, https://pharmaranks.com/drugs/nalmefene.
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 nalmefene on DailyMed (NIH) ↗.