On this page · 9 sections

Narcan (injection)

Generic name: naloxone (injection)

Brand names: Narcan, Zimhi

Used for opioid overdose
Last updated November 3, 2026 0 views
Share

What is naloxone?

Naloxone is used in emergencies to treat a known or suspected opioid overdose in adults or children.

This medicine should not be used instead of emergency medical care for an overdose.

Naloxone may also be used for reasons not mentioned in this medication guide.

This section was rewritten for readability and reviewed for meaning.

Warnings

Naloxone is used to reverse the effects of opioid medicine and to treat an opioid overdose. An opioid overdose can be fatal. Symptoms may include severe drowsiness, pinpoint pupils, slow breathing, or no breathing.

A person caring for you can give the naloxone if you stop breathing or do not wake up. Make sure anyone caring for you knows where you keep naloxone and how to use it.

Your caregiver must get emergency help after giving a naloxone injection and may need to perform CPR (cardiopulmonary resuscitation) on you while waiting for help to arrive. You may need another injection every 2 to 3 minutes until emergency help arrives.

This section was rewritten for readability and reviewed for meaning.

Before taking this medicine

You should not be treated with naloxone if you are allergic to it.

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

  • you have heart problems.

If you use opioid medicine during pregnancy, your baby could be born with life-threatening withdrawal symptoms and may need medical treatment for several weeks.

Using naloxone injection while you are pregnant may also cause opioid withdrawal symptoms 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 naloxone injection. Be sure all emergency medical caregivers know that you are pregnant and that any follow-up doctor knows you received this medicine.

Ask a doctor if it is safe to breastfeed while using this medicine.

This section was rewritten for readability and reviewed for meaning.

Naloxone side effects

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

Because naloxone reverses opioid effects, this medicine may cause sudden withdrawal symptoms such as:

  • nausea, vomiting, diarrhea, stomach cramps;
  • fever, sneezing, sweating, body aches, weakness;
  • tremors or shivering, fast heart rate, pounding heartbeats, increased blood pressure;
  • goose bumps;
  • runny nose, yawning; or
  • feeling nervous, restless, or irritable.

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

Common side effects of Narcan may include:

  • nausea, dizziness;
  • skin redness where an injection was given;
  • feeling lightheaded; or
  • yellowing of the skin or eyes.

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.

This section was rewritten for readability and reviewed for meaning.

How is naloxone given?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Naloxone is injected into a muscle or under the skin, or into a vein. The injection may be given by a healthcare provider, emergency medical provider, or a family member or caregiver who is trained to properly give a naloxone injection.

Naloxone is injected into a vein by a healthcare provider.

If you are a caregiver or family member read all instructions when you first get this medicine. If provided, use the "trainer" device to practice giving an injection so you will know how to do it in an emergency. Ask your doctor or pharmacist if you have any questions. Seek medical help right away if an accidental needlestick injury occurs.

Be sure you know how to recognize the signs of an opioid overdose in the person you are caring for. Overdose symptoms may include:

  • slowed breathing, or no breathing;
  • very small or pinpoint pupils in the eyes;
  • slow heartbeats; or
  • extreme drowsiness, especially if you are unable to wake the person from sleep.

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

Do not assume that an overdose episode has ended if symptoms improve. You caregiver must still get emergency help after giving a naloxone injection, even if the person wakes up. You may need to perform CPR (cardiopulmonary resuscitation) on the person while you are waiting for emergency help to arrive.

Naloxone injection is given in the outer thigh. In an emergency, you may give an injection through the person's clothing.

After injecting naloxone, stay with the person and watch for continued signs of overdose. You may need to give another injection every 2 to 3 minutes until emergency help arrives. Read and carefully follow the instructions provided with this medicine.

Throw away a prefilled syringe after one use, even if there is still medicine left inside.

Store at room temperature away from moisture, heat, and light. Keep the auto-injector in its outer case until you are ready to use it.

What happens if I miss a dose?

Naloxone is used as needed and does not have a daily dose.

This section was rewritten for readability and reviewed for meaning.

What happens if I overdose?

Since naloxone comes in a single-dose auto-injector, it is unlikely to cause an overdose.

Do not leave a person alone after giving them a naloxone injection. An opioid overdose can affect a person's thinking or reactions.

This section was rewritten for readability and reviewed for meaning.

What other drugs will affect naloxone?

Other drugs may affect naloxone, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all other medicines you use.

This section was rewritten for readability and reviewed for meaning.

Common questions about Narcan

Can I get free Narcan or naloxone emergency kits?
Naloxone can quickly reverse an opioid overdose and may be available free through community programs, pharmacies, or state health departments. Some nasal spray products are sold over the counter, while others require a prescription. Always call 911 after giving naloxone because emergency medical care is still needed. Continue reading
How long does Narcan (naloxone) block opiates?
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
Why is fentanyl so dangerous?
Fentanyl is a powerful opioid that can be deadly when misused or taken in an overdose. It can quickly slow or stop breathing, especially in people who are not used to its effects. Combining fentanyl with alcohol, benzodiazepines, gabapentinoids, other opioids, or other depressants greatly increases the risk of overdose and death. Continue reading
What are the symptoms of a fentanyl overdose?
Illicit Fentanyl, a potent synthetic opioid, is a leading cause of U.S. overdose deaths. Often mixed with other drugs, it can rapidly depress breathing and cause death. Recognizing overdose signs like extreme drowsiness, slowed breathing, constricted pupils, cyanosis (blue lips, skin, fingernails), seizures, or coma is critical for timely emergency intervention. Continue reading
How do you administer Narcan (naloxone)?
Spray Narcan into one nostril while the person is lying on their back. Call 911 immediately, give another dose after 2 to 3 minutes if needed, and stay with the person until emergency help arrives. Narcan can restore breathing during an opioid overdose, but emergency medical care is still needed. Continue reading
How does Narcan (naloxone) work in an overdose?
Narcan (naloxone) works in an overdose by pushing opioids off the opioid receptors in your brain and taking their place. Opioids attach to these receptors and tell your lungs to slow down. When breathing slows or stops, the body runs out of oxygen, and that is what makes an opioid overdose deadly. Naloxone blocks those receptors without switching them on, so breathing can restart. It usually works in 2 to 3 minutes. Continue reading
How do you administer Narcan Nasal Spray?
Narcan nasal spray is an over‑the‑counter naloxone medicine used to reverse an opioid overdose and help someone start breathing again. This guide explains when to use Narcan nasal spray, step‑by‑step instructions for how to give it, how often you can repeat doses, and what to do after you spray it so you can respond quickly in an opioid emergency. Continue reading
Is naloxone a controlled substance?
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.
Is naloxone an opioid antagonist?
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.

Related medicines

Before you take this medicine: the information on this page is general and may not cover your personal circumstances. Read the label supplied with your medicine and ask a pharmacist or doctor if you are unsure, especially if you are pregnant, breastfeeding, taking other medicines or managing a long-term condition.
General medicine information Consumer-friendly language

Content is provided for education and is not medical advice. See our medical disclaimer.