Naltrexone vs. naloxone
Alcohol Use Disorder
They sound alike and both block opioid receptors, but they do very different jobs. Naltrexone is for long-term recovery, and naloxone is for a crisis right now.
Naltrexone vs. naloxone
Two similar names, two very different jobs
Naltrexone
Ongoing treatment
Naloxone (Narcan)
Overdose rescue
Both are
Opioid antagonists
Naltrexone form
Pill or monthly shot
Naloxone form
Nasal spray
Naltrexone speed
Hours to days
Naloxone speed
2 to 5 minutes
Interchangeable?
No
Same basic action. Opposite real-world jobs.
2 to 5 min
for naloxone to reverse an opioid overdose in an emergency
1 month
a single naltrexone injection can keep working
2 jobs
same opioid-blocking action, opposite real-world uses
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.
Same basic action, opposite real-world jobs. Both are opioid antagonists, but naltrexone is built to last for daily recovery, while naloxone is built to act in minutes and wear off fast.
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.
In an overdose, only naloxone helps. Naltrexone takes too long to build its effect to rescue anyone. If someone is overdosing, use naloxone if it is available and call 911 right away.
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.
Looking for naltrexone by telehealth? See our naltrexone online service page.
Naltrexone treatment is coming to Recovery Delivered
See a provider by video, or handle everything by secure message. Your choice, same care, medication mailed to your door. Join the waitlist to be first in line when we open.
No spam. We will only email you about naltrexone for alcohol at Recovery Delivered.
Frequently asked questions
Is naltrexone the same as naloxone?
Is naltrexone the same as naloxone?
No. Naltrexone is a long-acting daily or monthly medicine used to treat alcohol and opioid use disorder. Naloxone (Narcan) is a fast, short-acting rescue medicine used to reverse an opioid overdose. They are different drugs for different jobs.
What is the difference between naltrexone and naloxone?
What is the difference between naltrexone and naloxone?
Naltrexone works slowly and lasts a long time, so it is used for ongoing recovery. Naloxone works within minutes but wears off in under two hours, so it is used only in an emergency overdose. Both block opioid receptors, but their timing and purpose are opposite.
Can naloxone treat alcohol use disorder?
Can naloxone treat alcohol use disorder?
No. Naloxone is an emergency overdose medicine and wears off quickly. Naltrexone is the medication used to treat alcohol use disorder, because its blocking effect lasts long enough to reduce cravings and heavy drinking over time.
Which one reverses an overdose?
Which one reverses an overdose?
Naloxone (Narcan) reverses an opioid overdose. Naltrexone does not. If someone is overdosing, use naloxone if available and call 911 immediately.
- 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.