Naltrexone and naloxone sound almost the same, and both block opioid receptors, but they do very different jobs. In one line: naltrexone is for long-term recovery, and naloxone is for a crisis happening right now. They are not interchangeable.
Naltrexone vs. naloxone at a glance
Naltrexone is a long-acting medicine you take daily or monthly to treat alcohol or opioid use disorder. Naloxone, known by the brand Narcan, is a fast, short-acting rescue medicine used to reverse an opioid overdose in an emergency. Here is how the two compare, side by side.
| Feature | Naltrexone | Naloxone (Narcan) |
|---|---|---|
| Main use | Ongoing treatment for alcohol or opioid use disorder | Emergency reversal of opioid overdose |
| How it is given | Daily pill or monthly injection | Nasal spray or injection |
| How fast it works | Builds its effect over hours to days | Within 2 to 5 minutes |
| How long it lasts | 24 hours (pill) to 1 month (injection) | 30 to 90 minutes |
| When it is used | Planned, daily or before drinking | Right now, during an overdose |
| Prescription | Prescription only | Available over the counter |
| Purpose | Reduce cravings and prevent relapse | Save a life in an emergency |
What is naltrexone?
Naltrexone is a prescription medicine used to treat alcohol use disorder and opioid use disorder. It blocks opioid receptors steadily over time, which removes the reward from alcohol and opioids and lowers cravings. It comes as a 50 mg daily pill or a once-a-month injection called Vivitrol. It is not addictive and not a controlled substance. Because its effect lasts, it is used as an ongoing treatment, not an emergency drug. Read our full naltrexone for alcohol guide.
What is naloxone (Narcan)?
Naloxone is an emergency medicine that reverses an opioid overdose. When someone has taken too much of an opioid and their breathing slows or stops, naloxone knocks the opioid off the receptors within minutes and restores normal breathing. It is given as a nasal spray or an injection, and it is now available over the counter so families and bystanders can keep it on hand. Its effect is short, only 30 to 90 minutes, which is often shorter than the opioid itself, so a person may need more than one dose and still needs emergency care.
Why are they so easily confused?
The names differ by just a few letters, and both drugs are opioid antagonists, meaning both block opioid receptors. That shared mechanism is where the similarity ends. Naltrexone is designed to last a long time so it can support recovery day after day. Naloxone is designed to act instantly and wear off quickly so it can rescue someone in an overdose.
Can you use one instead of the other?
No. They are not substitutes. Naloxone will not treat alcohol or opioid use disorder, because it wears off in under two hours. Naltrexone will not rescue someone from an overdose, because it takes too long to build its effect and is taken as a planned dose, not an emergency one.
Is naloxone the same as the naloxone in Suboxone?
It is the same drug, used differently. Suboxone is a combination of buprenorphine and a small amount of naloxone. In that pill, the naloxone is included to discourage misuse, not to reverse an overdose. So you may see the word naloxone on a Suboxone label, but that is a different use from the standalone Narcan rescue spray.
For the bigger picture, see our naltrexone guide and the main alcohol treatment guide.
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No spam. We will only email you about naltrexone for alcohol at Recovery Delivered.Frequently asked questions
Is naltrexone the same as naloxone?
What is the difference between naltrexone and naloxone?
Can naloxone treat alcohol use disorder?
Which one reverses an overdose?
Daniel R. Karlin, MD, MA
Board-certified psychiatrist and addiction medicine specialist. Author of 21+ peer-reviewed publications (1,355 citations) including recent work in JAMA (2025) and the British Journal of Psychiatry (2023).
- Sources.
- U.S. Food and Drug Administration. Naloxone (Narcan) over-the-counter approval and prescribing information.
- U.S. Food and Drug Administration. Prescribing information for naltrexone (ReVia) and naltrexone extended-release injectable (Vivitrol).
- Singh D, Saadabadi A. Naltrexone. StatPearls. National Library of Medicine.
This page is for education only and is not medical advice. If you think someone is overdosing, call 911 right away.
