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How long does Narcan (naloxone) block opiates?

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on March 30, 2023.

Official answer


Key Points

  • Narcan (naloxone) blocks opioid receptors from 30 to 120 minutes, but this can be variable and depends upon the dose and how it is given. Some patients may need repeat doses of naloxone.
  • Seek immediate emergency medical assistance (call 911) after giving the first dose of naloxone and keep the person under surveillance until emergency help arrives.
  • The duration of action of naloxone may not be as long as the duration of action of most opioids (narcotics) involved in an overdose. This can increase the risk for further problems with breathing, extreme sedation or inability to respond when the naloxone starts to wear off.

What is naloxone?

Narcan (generic name: naloxone) is a treatment often used to reverse the effects of an opioid overdose. It is available as an injection and as nasal spray. It was approved by the FDA as an over-the-counter (OTC) product in March 2023.

Prescription opioids are narcotic drugs often used for moderate-to-severe pain and include medicines such as hydrocodone, oxycodone, fentanyl and morphine. Heroin, an illegal drug of abuse, is also an opiate.

Narcan (naloxone) is classified as an opioid antagonist which means that it blocks opiate receptors in the brain and other areas of the body. Naloxone and opioids compete for the same receptor sites. By occupying the receptor and blocking the action of the opioid, naloxone can help to reverse the dangerous effects of an opioid overdose.

Evidence suggests that naloxone reverses opioid effects by competing for the opiate receptor sites in the central nervous system (CNS), with the greatest affinity for the mu receptor.

Related: Know Your Narcan (naloxone): Save a Life

Does Narcan work for buprenorphine overdose?

The effects of Narcan on slowed or stopped breathing by partial agonists or mixed agonist/ / antagonists, such as buprenorphine and pentazocine, may be incomplete and may require repeat doses or higher doses of Narcan (naloxone).

For example, buprenorphine has a long duration of action in the body and is more slowly displaced from the opioid receptor. Larger or repeat doses of naloxone may be needed to block buprenorphine effects and to reverse prolonged respiratory depression.

In April 2021, Kloxxado (naloxone nasal spray) from Hikma Pharmaceuticals was approved to treat known or suspected opioid overdoses in adults and children.

  • Kloxxado nasal spray contains 8 mg per spray, which is double the amount in Narcan Nasal. Maximum concentrations occur in about 15 minutes.
  • Like Narcan Nasal Spray, extra doses may be given if the person remains unresponsive while waiting for emergency medical assistance to arrive. Extra doses of naloxone are often required in the emergency opioid overdose situation, as the duration of action of the opioid is often longer than the duration of naloxone.

Where can I get Narcan?

Narcan (naloxone) is now available at most major U.S. pharmacies without a prescription. If you or anyone in your family takes opioid medications, you should strongly consider having naloxone on hand for an emergency situation. Overdoses can occur by accident or intentionally.

Naloxone comes in different forms and can be given either as an injection or a nasal spray. Some forms of naloxone, such as Narcan Nasal Spray, are more user-friendly and can be given by the lay public, family members, caregivers or friends until emergency medical help arrives.

In March 2023, the FDA approved an over-the-counter (OTC) version of Narcan Nasal Spray, but it is not expected to be on retail shelves until late summer 2023. In the meantime, the prescription product will remain readily available from the pharmacist and through community distribution programs in accordance with state laws.

Patients and family members or caregivers, once they get their naloxone product, should read the FDA-approved patient labeling or Drug Facts Label before an emergency occurs. In those that elect to carry the devices or store these medications in their home, learning how to use them ahead of time can save important time.

How much does Narcan cost?

Narcan Nasal Spray

  • Narcan Nasal Spray is available from your pharmacist in every U.S. state. You do not need a prescription from your doctor.
  • Narcan Nasal Spray is covered by most insurance plans with an insurance copay of $20 or less. Government insurance plans also cover Narcan Nasal Spray.
  • If you are paying cash, Narcan Nasal Spray 4 mg averages about $130 to $140 for a carton of 2 sprays using the online discount coupon.
  • The cost for the OTC version of Narcan Nasal Spray 4 mg, expected on shelves in late summer 2023, has not yet been reported by the manufacturer, Emergent Biosciences.

Any form of naloxone is NOT a substitute for emergency medical care, and 911 or other emergency medical care should be contacted immediately after administering naloxone in any form. Keep the person who has overdosed under surveillance until emergency personnel arrive.

This is not all the information you need to know about naloxone for safe and effective use in an emergency overdose. Review the full Narcan (naloxone) information here before an emergency overdose situation occurs, and discuss this information with your doctor or other health care provider.

  • Schiller EY, Goyal A, Mechanic OJ. Opioid Overdose. [Updated 2020 Nov 20]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from:
  • Kloxxado (naloxone) [package insert]. FDA. Accessed May 5, 2021 at
  • Narcan (naloxone) [Package Insert]. Revised March 2020. Adapt Pharma. Plymouth Meeting, PA Accessed April 19, 2021 at
  • Naloxone injection. [Package insert]. DailyMed. US National Library of Medicine. Accessed June 10, 2020 at
  • Naloxone hydrochloride. Injection. Accessed June 10, 2020 at

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