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What Is Naloxone?

Naloxone is an opioid antagonist used to reverse the life-threatening effects of an opioid overdose. It can restore breathing when opioids such as fentanyl, heroin, morphine, or oxycodone suppress respiration. Naloxone is available in nasal spray and injectable formulations. Some nasal sprays can be purchased without a prescription in the United States.

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What Is Naloxone?

Naloxone is an opioid antagonist used to reverse the life-threatening effects of an opioid overdose. It can restore breathing when opioids such as fentanyl, heroin, morphine, or oxycodone suppress respiration. Naloxone is available in nasal spray and injectable formulations. Some nasal sprays can be purchased without a prescription in the United States.

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How Does Naloxone Reverse an Overdose?

Naloxone attaches to opioid receptors and displaces opioid drugs from those receptors. This reverses opioid-induced respiratory depression and can help a person breathe again. Naloxone works only when opioids are involved and does not reverse overdoses caused solely by other substances. Its effects can wear off before the opioid leaves the body, so further medical care and additional doses may be needed.

When Should Naloxone Be Used?

Naloxone should be administered when an opioid overdose is suspected, especially when a person is unresponsive, breathing very slowly, or not breathing normally. Pinpoint pupils and unusual snoring or gurgling can also be warning signs. Give naloxone promptly, call emergency services, and follow dispatcher instructions for rescue breathing or cardiopulmonary resuscitation. Do not delay treatment while trying to confirm which drug was taken.

How Is Naloxone Administered?

Many naloxone nasal sprays are single-use devices that deliver medication into one nostril without assembly. Injectable versions have their own preparation and administration directions. Follow the instructions for the exact product available. When the person does not respond or develops breathing problems again, give another dose with a new device according to the product directions, commonly after two to three minutes. Continue emergency care until responders arrive.

What Are the Side Effects and Limitations of Naloxone?

Naloxone can trigger sudden opioid withdrawal in someone who is physically dependent on opioids. Symptoms can include agitation, sweating, nausea, vomiting, and a fast heartbeat. An overdose can return after naloxone wears off, particularly with long-acting or potent opioids. Naloxone is an emergency reversal medicine, not a substitute for medical evaluation or ongoing treatment for opioid use disorder.

Common Questions About Naloxone

Can naloxone reverse a fentanyl overdose?

Yes. Naloxone can reverse respiratory depression caused by fentanyl. More than one dose may be needed, and emergency medical care is necessary.

Is naloxone available without a prescription?

Certain naloxone nasal spray products are approved for over-the-counter sale in the United States. Availability depends on the specific product and retailer.

What happens after someone receives naloxone?

Breathing can improve within minutes when opioids caused the overdose. Emergency responders should still evaluate the person because overdose symptoms can return.

Will naloxone harm someone who has not taken opioids?

Naloxone usually has little or no pharmacologic effect in a person without opioids in their system. Give it when an opioid overdose is suspected and immediately contact emergency services.

References

DailyMed - NALOXONE HYDROCHLORIDE nasal spray. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8091a73d-9ecd-4578-a57b-5d85a2c5a16a. Date Accessed October 16, 2026.

Naloxone. PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/Naloxone. Date Accessed October 16, 2026.

Naloxone. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK441910/. Date Accessed October 16, 2026.

Naloxone Injection. MedlinePlus. https://medlineplus.gov/druginfo/meds/a612022.html. Date Accessed October 16, 2026.

Naloxone Nasal Spray. MedlinePlus. https://medlineplus.gov/druginfo/meds/a616003.html. Date Accessed October 16, 2026.