Naloxone vs. Naltrexone

Medically Reviewed by Smitha Bhandari, MD on April 29, 2022
5 min read

Naloxone (Narcan, Evzio) and naltrexone (ReVia, Depade) are two drugs used to help people with opioid addictions. They’re both in a class of drugs called opioid antagonists, but they do different things.

Naloxone is a drug that can temporarily reverse the effects of an opioid overdose. Anyone can give this very fast-acting medication, as a shot or nasal spray. It can save lives if it’s given quickly enough.

Naltrexone is not an emergency drug. It’s prescribed as part of a treatment plan to help you stop using a drug or consuming alcohol if you have a substance use disorder.

When you take an opioid, it binds to opioid receptors in your brain. Opioid receptors help your body control pain and addictive behavior. Opioid antagonists block the opioids from binding to those receptors, keeping the drug from causing the euphoria, or “high.”

Naloxone has been in the news over the past few years because it’s an emergency use drug that can be given at home or on the street for a suspected overdose from drugs such as oxycodone, hydrocodone, or heroin, to name a few. Naloxone does work on fentanyl, but not as quickly or as well. The most dangerous symptom of an opioid overdose is shallow breathing and gasping, which can lead to respiratory failure altogether and death.

You don’t need to be a health care professional to give the drug. If you see someone who has recently overdosed, naloxone can restart or improve their breathing until they can get emergency care. If you don’t know what kind of drug the person took, you can still give naloxone. It will only work against opioids, but it won’t cause any harm if you give it to someone who doesn’t have opioids in their system. In this case, it’s better to err on the side of caution and give the medication.

Naloxone comes in two forms: as a shot and as a nasal spray. The CDC recommends that if you or someone you know is at risk for an opioid overdose, you should have naloxone close by. Almost 40% of people who overdose on opioids do so with someone nearby, so having naloxone on hand could save many lives. If you are the one at risk, make sure the people around you know that you have naloxone in case of emergency. You wouldn’t be able to give it to yourself.

The drug works fast, within a few minutes. If you don’t see a response within 3 minutes, you can give a second dose. The person who received naloxone should go to the closest emergency room (ER) right away. Naloxone is an emergency treatment, but it’s not a “one-and-done” type of drug. The effects only last 30-90 minutes. After that, it’s possible for the overdose symptoms to come back. If it seems like the drug is wearing off before emergency help comes or you get to a hospital, and the person is having a hard time breathing again, you can give a second dose.

People who receive naloxone can also have withdrawal symptoms, since the opioid effect was removed so quickly. These symptoms can include:

You can get naloxone in all states. In some states, you don’t even need a prescription and you can get it at the pharmacy or from some community drug safety programs.

Naltrexone also helps people with drug or alcohol addiction, but differently from naloxone. As part of a treatment plan, naltrexone blocks opioids and alcohol from providing the “high” people want when using the substances. Now, it’s important to understand that naltrexone doesn’t keep you from actually getting drunk. You may not feel drunk because you don’t have that high feeling, but you can still be under the influence. It's not safe to drive or do other things that require you to be mentally alert.

You’ll need a prescription for naltrexone. It comes in tablets or as a shot.

If you take naltrexone to help you manage an addiction, you’ll likely have withdrawal symptoms. How strong the symptoms are and how long they last depend on which drug you were using, how much of it, and how long you’ve been taking it. Talk to your doctor about what to do when the withdrawal symptoms kick in.

Don’t use opioids for at least 7-10 days before starting naltrexone. If you take methadone, you also must stop taking it. You may be asked for a test before you start the treatment to make sure there are no opioids in your system.

The amount of naltrexone you take depends on why you need it (for either alcohol or opioids) and the strength of the medicine. It can be taken just once a day (by pill) or more often. You can also get naltrexone as a shot, given by a health care provider, once every 4 weeks.

As with all medications, naltrexone can cause some side effects. They include:

If you have side effects, talk to your doctor as soon as possible. Naltrexone can affect your liver, so if you notice your pee is very dark, your skin and eyes are yellow, or you have pain in your upper stomach, call your doctor right away.

Don’t stop taking naltrexone without checking with your doctor first, even if you’re feeling better. If you stop taking it, you could relapse and use drugs or drink alcohol again.

If you need medical or dental care while taking naltrexone, be sure that all health care providers, including your pharmacist, know you’re taking it. If you use opioids or alcohol while taking naltrexone, you may have stronger side effects, such as sedation.