Nalmefene and naloxone are both opioid receptor antagonists approved to reverse opioid overdose, but they differ in duration of action, availability, and clinical experience. Nalmefene lasts substantially longer in the body, while naloxone has been used for decades and is widely available, including in nonprescription nasal-spray products.
What is nalmefene?
Nalmefene is an opioid antagonist that can reverse respiratory depression and other life-threatening effects of opioid overdose. FDA approved a nalmefene nasal spray in 2023 for emergency treatment of known or suspected opioid overdose.
What is naloxone?
Naloxone is also an opioid antagonist and is the most widely used opioid-overdose reversal medication. It is available in nasal and injectable forms, and several nasal-spray products are available over the counter.
How long do nalmefene and naloxone last?
Nalmefene has a longer half-life than naloxone. FDA materials note that nalmefene remains active much longer, which may theoretically reduce the chance that opioid effects return after the reversal medicine wears off.
However, a longer duration also means precipitated opioid withdrawal may be more prolonged.
Does nalmefene work better than naloxone for fentanyl?
Both can reverse opioid overdose. Current federal guidance does not say that nalmefene should universally replace naloxone for fentanyl overdoses. Naloxone remains widely recommended and accessible, and additional doses may be needed with potent or long-lasting opioids.
Can either medication cause withdrawal?
Yes. Both can rapidly displace opioids from receptors and trigger acute withdrawal in a person who is physically dependent on opioids. Because nalmefene lasts longer, SAMHSA notes that withdrawal can potentially be more severe or prolonged.
Is nalmefene available over the counter?
No. Current nalmefene nasal products are prescription medications. Naloxone has multiple FDA-approved nonprescription nasal products.
Do either of these medicines replace emergency care?
No. Suspected opioid overdose is a medical emergency. Call 911, administer an approved opioid-overdose reversal medication if available, and provide rescue breathing or CPR if trained and needed.
Do they work for xylazine, medetomidine, or benzodiazepines?
No. Naloxone and nalmefene reverse opioid effects. They do not directly reverse non-opioid sedatives. They should still be given when an opioid may be involved in a mixed overdose.
Frequently asked questions
Which medication should a bystander use?
Use the FDA-approved opioid-overdose reversal medication that is available and follow the product instructions. Do not delay emergency response while comparing products.
Is nalmefene newer than naloxone?
Yes. Naloxone has decades of overdose-reversal use, while intranasal nalmefene is a newer option.
Can more than one dose be required?
Yes. Follow the product labeling and emergency guidance if the person does not respond or symptoms return.
Does Trinity Behavioral Health provide nalmefene?
This educational article does not establish that Trinity provides or dispenses any specific overdose-reversal medication. Current services should be verified directly.
Sources
- FDA: Information About Naloxone and Nalmefene
- SAMHSA: Opioid Overdose Reversal Medications
- SAMHSA: Opioid Overdose Prevention and Reversal
This article is general educational information and does not replace emergency medical care.