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Generic name: naloxone hydrochloride
Dosage form: injection
Drug class: Antidotes

Medically reviewed by Judith Stewart, BPharm. Last updated on Feb 7, 2023.

What is Zimhi?

Important information

Zimhi is used to temporarily reverse the effects of opioid medicines. The medicine in Zimhi has no effect in people who are not taking opioid medicines. Always carry Zimhi with you in case of an opioid emergency.

Who should not use Zimhi?

Do not use Zimhi if you are allergic to naloxone hydrochloride or any of the ingredients. See the end of this page for a complete list of ingredients.

What should I tell my healthcare provider before using Zimhi?

Before using Zimhi, tell your healthcare provider about all of your medical conditions, including if you:

Tell your healthcare provider about the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

How should I use Zimhi?

Read the Instructions for Use at the end of this Patient Information leaflet for detailed information about the right way to use Zimhi.

Dosing information

- Administer Zimhi (naloxone hydrochloride) 5 mg/0.5 mL to adult or pediatric patients into the anterolateral aspect of the thigh, through clothing if necessary.

Use: Zimhi is indicated in adult and pediatric patients for the emergency treatment of known or suspected opioid overdose, as manifested by respiratory and/or central nervous system depression.
Zimhi is intended for immediate administration as emergency therapy in settings where opioids may be present. Zimhi is not a substitute for emergency medical care.

Zimhi side effects

Zimhi may cause serious side effects, including:

The most common side effects include: nausea, dizziness, lightheadedness, and increased amounts of red blood cell breakdown products (bilirubin) in your blood.

In infants under 4 weeks old who have been receiving opioids regularly, sudden opioid withdrawal may be life-threatening if not treated the right way. Signs and symptoms include: seizures, crying more than usual and increased reflexes.

These are not all of the possible side effects. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

How should I store Zimhi?

Keep Zimhi and all medicines out of the reach of children.

General information about the safe and effective use of Zimhi

Medicines are sometimes prescribed for purposes other than those listed in a Patient Information leaflet. Do not use this medicine for a condition for which it was not prescribed. You can ask your pharmacist or healthcare provider for information that is written for health professionals.

What are the ingredients in Zimhi?

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.


Use Zimhi for known or suspected opioid overdose in adults and children.

Zimhi is intended to be administered by people 12 years of age or older. Younger children or those with limited hand strength may find the device difficult to use.

Read this Instructions for Use carefully before you use this product.

Before you need to use your Zimhi syringe make sure your healthcare provider shows you the right way to use it.

Parents, caregivers, and others who may be in a position to administer Zimhi should also understand how to use it. If you have questions, ask your healthcare provider.

Zimhi works like a standard prefilled syringe. Zimhi is injected downwards, into the middle of the outer thigh, through clothing if needed.

Step by step instructions:

  1. Place the patient on their back. When ready to inject, pull off cap to expose needle.
  2. Do not put finger on top of the device. In children under the age of 1 year old, pinch the thigh muscle while administering the dose.
    Hold Zimhi by finger grips only and slowly insert the needle into the thigh.
  3. After needle is in thigh: Push the plunger all the way down until it clicks and hold for 2 seconds.
  4. Right after the injection, using one hand with fingers behind the needle, slide the safety guard over the needle. Do not use two hands to activate the safety guard. Put the used syringe into the blue case and close the case.
  5. Get emergency medical help now.  Tell healthcare provider that you gave an injection of naloxone hydrochloride.
    Turn the patient on their side (recovery position) after giving Zimhi. Use second syringe if needed.
    You may need a second Zimhi syringe if symptoms continue or return.

If symptoms return after an injection with Zimhi, an additional injection using another Zimhi prefilled syringe may be needed. Give additional injections using a new Zimhi prefilled syringe every 2 to 3 minutes and continue to closely watch the person until emergency help is received. Using Zimhi does not take the place of emergency medical care.

After Use and Disposal

For more information see Patient Information sheet or ask your healthcare provider.

How to Store

Keep Zimhi in its plastic case nearby and ready for use at all times.

Check Your Stored Zimhi Often - The solution should be clear when viewed through the window on the device. If the solution is discolored (yellowish or brown color), cloudy or contains particles, replace the Zimhi with a new one.

Your Zimhi Has an Expiration Date — Example YYYY-MM. Replace Zimhi before the last day of expiration month.
Dispose of expired Zimhi properly by taking the Zimhi in its case to a healthcare provider or hospital emergency room.

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

More FAQ

Further information

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