Naltrexone vs Naloxone: Differences, Uses and Safety

Naltrexone vs naloxone is a common point of confusion because the names are close and both medications block opioid receptors. They are used for very different things. Naloxone (often sold as Narcan) is an emergency medicine that reverses an opioid overdose. Naltrexone is a prescription medication used over weeks or months to treat alcohol use disorder or opioid use disorder.

If someone may be overdosing, call 911 now. Give naloxone if you have it and stay with the person.

Naltrexone vs Naloxone at a Glance

	Naloxone	Naltrexone
Main use	Emergency reversal of an opioid overdose	Treatment of alcohol use disorder or opioid use disorder
Common forms	Nasal spray (such as Narcan) or injection	Daily pill, or an extended-release injection given about once a month
Timing	Works for about 30 to 90 minutes (NIDA)	Pill once a day, or injection about once a month (SAMHSA)
Prescription	4 mg Narcan nasal spray is sold without a prescription (FDA, 2023)	Prescription required
Who gives it	Anyone nearby, including family and bystanders	Prescribed by a licensed practitioner as part of a treatment plan

What Is Naloxone Used For?

Naloxone is an opioid antagonist. The National Institute on Drug Abuse (NIDA) explains that it attaches to opioid receptors and reverses and blocks the effects of other opioids, which can restore breathing during an overdose. It can be given as a nasal spray or as an injection.

In March 2023 the FDA approved Narcan 4 mg nasal spray for over-the-counter use, so it can be bought without a prescription in drug stores, grocery stores and online.

Important limits, according to NIDA:

• It wears off. Naloxone works for about 30 to 90 minutes, and many opioids stay in the body longer, so overdose symptoms can return. Stronger opioids such as fentanyl may need more than one dose.
• Call 911 anyway. Calling 911 is one of the most important steps, even if the person wakes up.
• It only works on opioids. It will not reverse an overdose from cocaine or methamphetamine alone, and it has no effect on someone without opioids in their system.
• Withdrawal can follow. People who are physically dependent on opioids may have withdrawal symptoms within minutes, such as sweating, nausea, vomiting and a rapid heart rate.

Learn the warning signs in our guide to signs of opioid overdose.

What Is Naltrexone Used For?

Naltrexone is also an opioid antagonist, but it is used as an ongoing treatment, not in an emergency. SAMHSA notes that it is FDA-approved for alcohol use disorder and opioid use disorder, and that any practitioner licensed to prescribe medications can prescribe it.

• For alcohol use disorder: the SAMHSA and NIAAA guide describes a usual oral dose of 50 mg once a day, or an extended-release 380 mg injection given about once a month. It blocks receptors involved in the rewarding effects of drinking and in craving.
• For opioid use disorder: SAMHSA's TIP 63 describes the extended-release injection as the form with the stronger evidence, because daily pills are often hard to take consistently.

Naltrexone is not a scheduled (controlled) medication, according to TIP 63.

Why Does Naltrexone Require Time Without Opioids?

Because naltrexone blocks opioids, starting it while opioids are still in the body can cause sudden, severe withdrawal. SAMHSA's TIP 63 says people generally need at least 7 days without short-acting opioids and 10 to 14 days without long-acting opioids before starting naltrexone for opioid use disorder. The SAMHSA alcohol guide warns that withdrawal triggered this way can be severe enough to require hospitalization.

TIP 63 also lists vulnerability to opioid overdose as a risk with naltrexone, and notes that people who complete medically supervised withdrawal are at risk of overdose. Lower tolerance means a dose someone used before can be dangerous. Keep naloxone on hand and talk with a prescriber before stopping or missing doses.

Is Naloxone in Suboxone?

Yes. Some buprenorphine products, such as Suboxone, combine buprenorphine with naloxone. That is different from naltrexone, which contains no opioid. Our article on opioid detox medications such as Suboxone and methadone explains how those medications differ.

Where Detox Fits Before Treatment Medications

Medications like naltrexone are decisions for you and a prescriber, made after an assessment of your substance use, health and other medications. For many people, the first step is safely getting through withdrawal.

Surf City Detox provides medical detox and residential treatment at two Huntington Beach locations. If you are struggling with opioids or alcohol, an admissions call can help you understand the right level of care. When you call, expect questions about:

• which substances you use, how much and how recently
• prescriptions and past withdrawal symptoms or overdoses
• medical and mental health conditions
• your insurance details, so admissions can check plan-specific benefits

Ask about follow-up care after detox, including who would manage any medication such as naltrexone. Admission, the receiving location and any costs are confirmed individually.

Talk to Surf City Detox

If you or someone you love is ready to stop using opioids or alcohol, call Surf City Detox at 888-222-1506 or contact us online. You can also read how admissions works.

Medical disclaimer: This article is for general information and is not medical advice. Do not start, stop or change any medication without talking to a qualified healthcare provider. For a medical emergency, call 911.