• What Is Naloxone and How Does It Reverse an Opioid Overdose?

    A person wearing an American Red Cross shirt holding a naloxone nasal spray training device.

    Date Published: September 9, 2026

    Opioid overdoses can happen anywhere, whether from prescription pain medicine, illegal opioids or opioids used in the wrong way. Understanding how naloxone works and when to use it can help you act quickly in an emergency.

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    What Is Naloxone?

    Naloxone is a medicine used in suspected opioid overdose emergencies. It can temporarily reverse the effects of opioids, and help a person breathe more normally until emergency medical help arrives. Naloxone is most commonly available as a nasal spray designed to be easy for the public to use. It may be available for free through public health programs, community organizations, pharmacies or harm reduction programs. Even if naloxone seems to work, the person still needs emergency medical care. Always stay with the person until help arrives.

    How Does Naloxone Reverse an Opioid Overdose?

    Naloxone temporarily blocks the effects of opioids in the brain. In an overdose, opioids can slow or stop breathing. Naloxone can help restore breathing and responsiveness within minutes, but it does not last as long as some opioids, so emergency medical care is still needed.

    How Quickly Does Naloxone Work?

    Naloxone is fast acting and usually begins working within minutes, which is why it should be given as soon as an opioid overdose is suspected. However, its effects are temporary and may wear off before some opioids are fully out of the body, so signs of overdose can return.

    When Should Naloxone Be Used?

    If you think someone is experiencing an opioid overdose, call 911 then give naloxone as soon as possible. Stay with the person until help arrives. Learn more about the signs of opioid overdose so you can act quickly in the event of an emergency.

    Read more about the signs of opioid overdoses so you can recognize an overdose and act quickly in the event of an emergency.

    How Is Naloxone Administered?

    Naloxone is most commonly available as a nasal spray designed for community use. It is easy to use and may be available for free through many public health programs, community organizations, pharmacies or harm reduction programs. The American Red Cross also offers an Opioid Overdose Kit with NARCAN® Nasal Spray for individuals who want to be prepared for an opioid overdose emergency.

    Always follow the instructions that come with the product you have:

    • Narcan® Nasal Spray: A needle-free nasal spray commonly used in homes, schools and other community settings

    Can Anyone Give Naloxone?

    Naloxone nasal spray is designed to be used by anyone who might witness an opioid overdose, including family, friends, caregivers and bystanders. Learning how to recognize the signs of an overdose and give naloxone before an emergency happens can help you feel more confident if you need to respond.

    Why Is Medical Care Still Needed After Naloxone?

    Naloxone can quickly and temporarily reverse the effects of opioids, but its protection does not last forever. Because some opioids stay in the body longer than naloxone, signs of overdose can return after the medicine wears off.

    Learn How to Respond to an Opioid Overdose

    Prepare for an opioid overdose emergency with the First Aid for Opioid Overdoses Online Course. Through interactive lessons and practical scenarios, learners gain confidence to respond during an opioid overdose emergency. The course takes approximately 55 minutes to complete.

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    Frequently Asked Questions About Naloxone

    Naloxone vs. Narcan®: What's the difference?

    Naloxone is the generic name for a medicine that temporarily reverses the effects of an opioid overdose. Narcan® is a brand name for a nasal spray that contains naloxone.

    How does naloxone reverse an opioid overdose?

    Naloxone works by quickly attaching to the same receptors in the brain that opioids attach to. It can push opioids off those receptors and temporarily block their effects, helping restore breathing and responsiveness within minutes. Because naloxone does not stay active as long as some opioids, signs of overdose can return after it wears off.

    How quickly does naloxone work?

    Naloxone usually starts working within a few minutes. Call 911 and administer naloxone as soon as you see signs of an overdose and keep checking the person’s breathing and alertness until emergency help arrives.

    How long does naloxone last?

    Naloxone works quickly to temporarily reverse the effects of an opioid overdose, but its effects are temporary (between 30 and 90 minutes). Because some opioids can stay in the body longer than naloxone, signs of overdose can return after naloxone wears off.

    Overdose signs can reappear if opioids are still present in the body. Call 911 and stay with the person until emergency medical services (EMS) arrive.

    Does naloxone end the emergency?

    Naloxone does not end the emergency. It is temporary and additional doses may be needed. The person still needs emergency medical evaluation because breathing problems can return.

    Can naloxone save a life?

    Naloxone temporarily reverses an opioid overdose and improves someone’s chance of survival if given quickly. It is an important overdose reversal medication that provides critical time for emergency responders to arrive.

    Do you still need to call 911 after administering naloxone?

    You still need emergency medical care after giving naloxone. Some opioids last longer than naloxone, so overdose signs can reappear after the medicine wears off.

    Can someone stop breathing again after naloxone wears off?

    Yes. Someone can stop breathing again after naloxone wears off. Naloxone works for a limited time, and some opioids can stay active in the body longer than naloxone. If opioids are still affecting the person after naloxone wears off, signs of overdose — such as very slow or stopped breathing — can return. Call 911, keep checking the person’s breathing and responsiveness, and stay with them until emergency help arrives.

    Should you give naloxone if you are not sure?

    If you think someone might be having an opioid overdose, call 911 and give naloxone as soon as possible. You do not have to be certain that opioids caused the emergency before you act. Naloxone is safe to give if an opioid overdose is suspected, including to infants, children and adults. Waiting can delay lifesaving care. Emergency responders will check the person and provide any additional care needed.

    About the Expert

    This article incorporates guidance from Nathan Charlton, MD, an emergency medicine physician, medical toxicologist and addiction medicine specialist at the University of Virginia. Dr. Charlton has nearly 20 years of experience caring for patients experiencing opioid-related emergencies and those treated with naloxone. He is also Vice Chair of the American Red Cross Scientific Advisory Council, a group of experts that evaluates scientific evidence and provides guidance on first aid, CPR and emergency care recommendations for the American Red Cross.

    What to Read Next

    Who Should Carry Naloxone?
    Dr. Nathan Charlton explains who should carry naloxone and why having naloxone in a first aid kit can help in an opioid overdose situation.
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    How to Use Naloxone During a Suspected Opioid Overdose
    Naloxone is available in several forms and understanding how to use the product you have can make it easier to know when someone needs help.
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    Signs & Symptoms of Opioid Overdose
    With proper training, anyone can learn to spot an opioid overdose, respond safely and give care until advanced emergency help arrives.
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