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Generic name: naloxone [ nah-LOX-one ]
Brand names: Narcan, Rezenopy, Kloxxado, Zimhi
Dosage form: Injectable solution (Zimhi 5 mg/0.5 mL), Nasal spray (Narcan 4 mg, Rezenopy 10 mg, Kloxxado 8 mg)
Drug class: Antidotes

Medically reviewed by Melisa Puckey, BPharm. Last updated on May 22, 2024.

What is naloxone?

Naloxone is an FDA approved medicine used to quickly reverse an opioid overdose. Naloxone is a opioid antagonist that works by attaching to opioid receptors and therefore reverses and blocks the effects of other opioids. 

Naloxone should be used as soon as possible to treat a known or suspected opioid overdose emergency if there are signs of slowed breathing, severe sleepiness or the person is not able to respond (loss of consciousness). Once naloxone has been given the patient must receive emergency medical care straight away, even if they wake up.

Naloxone is not a controlled substance, according to the US Drug Enforcement Administration (DEA).

Naloxone is available as a nasal spray (Narcan 4mg, Rezenopy 10 mg, Kloxxado 8mg) or an injection (Zimhi 5 mg/0.5 mL).

Narcan nasal spray became approved by the FDA on March 29, 2023 as is an over-the-counter (OTC) medicine that is available without a prescription. Other naloxone products are still prescription medicines, but in many states, these products are available from a pharmacist without a prescription from your doctor, under state Naloxone Access Laws or alternate arrangements.

Opioids are sometimes called a narcotic. Examples of opioids are buprenorphine, codeine, fentanyl, oxycodone (Oxycontin), heroin, hydrocodone (Vicodin, Lortab), hydromorphone, meperidine, morphine, methadone, oxymorphone, and tramadol

What is Naloxone used for?

Naloxone is used to treat a known or suspected opioid overdose emergency in children or adults. Signs of an opioid overdose may include:

Even if you are not sure an opioid overdose has occurred, if the person is not breathing or is unresponsive, give the naloxone right away and then seek emergency medical care.

Naloxone has different uses when used in multi-ingredient medications including buprenorphine with naloxone (Suboxone, Zubsolv, Bunavail)  which is used to treat opioid addiction, and naloxone with oxycodone (Targiniq ER) which is used for pain.


In an emergency situation it may not be possible before you are treated to tell your caregivers about your health conditions or if you are pregnant or breast feeding. Make sure any doctor caring for you afterward knows that you have received this medicine.
A person caring for you can give the naloxone if you stop breathing or don't wake up. Make sure any person caring for you knows where you keep this medicine and how to use it.

Your caregiver must get emergency help after giving you this medicine. You may need another injection every 2 to 3 minutes until emergency help arrives.

Drinking alcohol can increase certain side effects of naloxone.

Naloxone may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.

If you are using any narcotic pain medication, the pain-relieving effects of the narcotic will be reversed while you are also receiving this medicine.

Before taking this medicine

You should not be treated with this medicine if you are allergic to naloxone or any inactive ingredients in the injection or nasal spray.

If possible, before you receive naloxone, tell your doctor if:

Using naloxone while you are pregnant may cause opioid withdrawal effects in your unborn baby. However, having an opioid overdose can be fatal to both mother and baby. It is much more important to treat an overdose in the mother. You must get emergency medical help after using this medicine. Be sure all emergency medical caregivers know that you are pregnant.

If you use opioid medicine while you are pregnant, your baby could become dependent on the drug. This can cause life-threatening withdrawal symptoms in the baby after it is born. Babies born dependent on opioids may need medical treatment for several weeks.

In an emergency, you may not be able to tell caregivers if you are pregnant or breastfeeding. Make sure any doctor caring for your pregnancy or your baby knows you received this medicine.

How is naloxone given?

Use naloxone exactly as prescribed by your doctor. Follow all directions on your prescription label and read all medication guides or instruction sheets.

If you are a caregiver or family member, read all instructions when you first get this medicine so you will know how to use it in an emergency. Ask your doctor or pharmacist if you have any questions.

Naloxone injection instructions

Naloxone nasal spray instructions

After giving a dose of naloxone

Dosing information

Usual Adult Dose for Opioid Overdose

Initial dose:


Nasal Spray:


Usual Adult Dose for Reversal of Opioid Sedation

Initial dose:

Intravenous Infusion:


Usual Pediatric Dose for Opioid Overdose




Usual Pediatric Dose for Reversal of Opioid Sedation



Intravenous Infusion:


What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while using naloxone?

Avoid leaving a person alone after giving him or her a naloxone dose. An overdose can impair a person's thinking or reactions.

Naloxone side effects

Get emergency medical help if you have signs of an allergic reaction to naloxone: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Because naloxone reverses opioid effects, the administration may cause sudden withdrawal symptoms such as:

Sudden withdrawal symptoms in a baby younger than 4 weeks old may be life-threatening if not treated the right way. Symptoms include crying, stiffness, overactive reflexes, and seizures. Call your doctor or get emergency medical help if you are unsure how to properly give this medicine to a baby.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect naloxone?

Other drugs may interact with naloxone, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.


Kloxxado nasal spray
Active ingredient: naloxone hydrochloride
Inactive ingredients: dehydrated alcohol (20% (w/w)), edetate disodium dihydrate, propylene glycol, purified water, and sodium hydroxide and hydrochloric acid to adjust pH. The pH range is from 4.0 to 5.5.

Narcan nasal spray
Active ingredient: naloxone hydrochloride
nactive ingredients: benzalkonium chloride (preservative), disodium ethylenediaminetetraacetate (stabilizer), sodium chloride, hydrochloric acid to adjust pH and sterile water.

Narcan is not made with natural rubber latex.

Rezenopy nasal spray
Active ingredient: naloxone hydrochloride
Inactive ingredients: glycerin, trisodium citrate dihydrate, hydrochloric acid, and sodium hydroxide to adjust pH, and purified water.

Rezenopy nasal spray is not made with natural rubber latex.

Zimhi injection
Active ingredient: naloxone hydrochloride
Inactive ingredients: sodium chloride, hydrochloric acid to adjust pH, and water for injection.
Zimhi is not made with natural rubber latex.







Kloxxado is distributed by Hikma Specialty USA Inc. Columbus, OH 43228

Narcan is distributed by Emergent Devices Inc., Plymouth Meeting, PA 19462 USA.

Rezenopy is manufactured by Summit Biosciences Inc.

Zimhi is a trademark of Adamis Pharmaceuticals Corporation. Manufactured for Adamis Pharmaceuticals, San Diego, CA 92130, USA. Distributed By USWM LLC, Louisville, KY 40241.

Popular FAQ

Naloxone is not a controlled substance, according to the US Drug Enforcement Administration (DEA). It is an opioid antagonist used to treat known or suspected opioid overdose, and naloxone nasal spray (sold under the brand name, Narcan) was FDA-approved for sale over-the-counter on March 29th, 2023. It should be available for purchase in places like drug stores, convenience stores, grocery stores and gas stations, as well as online, without a prescription from late summer. Narcan Nasal Spray and naloxone is still available from the pharmacist in all 50 states without a prescription from your doctor.

Naloxone is a centrally acting opioid receptor antagonist. Naloxone binds with the highest affinity to the mu-opioid receptor subtype in the central nervous system (CNS). Naloxone works to reverse opioid overdose and a form of naloxone (Narcan nasal spray) was FDA-approved for over-the-counter (OTC) sale on 29th March 2023.

There are several ways to get free Narcan (naloxone) emergency kits, which include, local syringe exchange programs, your insurance company, and state and local health departments or other community health services. Continue reading

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. Continue reading

Buprenorphine and naloxone is a combination medicine used for the maintenance treatment of opioid dependence in adults. It is available in sublingual film and sublingual tablet dosage forms under the brand names Suboxone, Zubsolv, Bunavail (discontinued), and Cassipa (discontinued). Continue reading

Narcan (naloxone) is available in different dose forms and can be given either as an injection or a nasal spray to reverse an opioid overdose. Continue reading

Narcan (naloxone) works in an overdose by reversing serious or deadly central nervous system (CNS) depression due to opioids (narcotics), including depressed breathing, extreme drowsiness and loss of consciousness. This effect usually occurs in minutes. Naloxone is considered a pure opioid antagonist and it works by blocking opioid receptors in the body. Continue reading

No, naloxone is not addictive. Naloxone is not an opioid and cannot be abused, unlike other medications that are used to treat an opioid use disorder. Continue reading

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Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.