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A drug used to treat overdoses of opioid medications. Naloxone is an opiate antagonist — that is, it binds to opiate receptors throughout the body and can block or reverse the effect of opioids.

When given to people who have overdosed on opioids, naloxone can save lives. It can quickly restore normal breathing to a person whose respiration has slowed or stopped.

Naloxone may be administered by an injection or a nasal spray. A number of companies offer generic brands of naloxone vials for use by professionals. Evzio is a pre-filled auto-injection device that family members or emergency personnel can use to inject naloxone quickly into the outer thigh. The device provides verbal instructions to users for delivering the medication. Narcan Nasal Spray is a prefilled device for delivering naloxone. Naloxone sometimes causes non-life-threatening side effects such as headache, rapid heart rate, nausea, vomiting and tremors.

Depending on the state where they live, friends, family members or community members may be allowed to use the auto-injector or nasal spray on someone who has overdosed. Some states require a prescription to naloxone, while others allow pharmacies to distribute it in an outpatient setting without a prescription. If you or a family member takes opioid medications regularly, ask your doctor whether it would be a good idea to keep naloxone on hand.

Want to learn more pain-related terms? See our Definitions section.

Robert S. Dinsmoor is a medical writer and editor based in Massachusetts.

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