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Updated on September 27, 2022

Narcan Uses, Side Effects & Risk Factors

What is Narcan?

Narcan is a nasal spray treatment that reverses the effects of opioid overdoses.

The name 'Narcan' refers to a specific formulation of the generic drug naloxone, although people commonly call other naloxone drugs “Narcan.” It is an opioid antagonist that binds to, and blocks, opioid receptors in the brain, preventing overdose.

Symptoms of an opioid overdose include:

  • Slow or shallow breathing
  • Vomiting
  • Unconsciousness
  • Faint heartbeat
  • Unusual sleepiness
  • Rapid heart rate
  • Very small (pinpoint) pupils
  • Low blood pressure
  • Inability to speak
  • Limp arms and legs
  • Purple lips and fingernails
  • Pale skin

Naloxone is available over-the-counter (OTC) in most states, and as a prescription drug in others under the brand names Narcan and Evzio.

If you decide to purchase naloxone, be sure to store the medication in its original packaging at room temperature. Read the drug information and any disclaimers on the packaging.

The Food and Drug Administration (FDA) has approved three forms of naloxone:

  • Nasal spray (Narcan)
  • Injectable
  • Auto-injectable (Evzio)

All three forms are highly effective at reversing an overdose.

However, Narcan nasal spray is easier for families, caregivers, and non-medical personnel to administer compared to injections, making it an ideal overdose treatment.

From 2012 to 2016, naloxone administration increased 75.1 percent, mirroring a 79.7 percent increase in the age-adjusted opioid mortality rate.

Centers for Disease Control and Prevention (CDC)

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How is Narcan Used?

To administer Narcan, lay the patient flat on their back and spray once into their nostril.
Make sure to support their neck and let the head tip back to ensure the drug enters the body.

Following dosing, contact emergency medical services (EMS) immediately, as overdoses are life-threatening. First responders are the proper health care professionals to help someone overdosing.

Narcan works immediately to stop an overdose but the first dose of naloxone is only effective for 30 to 90 minutes. If the patient doesn't respond or relapses into unresponsiveness, you must administer additional doses.

Each naloxone nasal spray contains a single dose and can only be used once. Therefore, you must use a new spray to give the patient a dose every two to three minutes, alternating nostrils each time.

Side Effects of Narcan

Narcan was given in a study to healthy adult volunteers to determine its side effects, which include:

  • Headache
  • Nasal dryness
  • Nasal congestion and edema (fluid)
  • Nasal inflammation
  • Increased blood pressure
  • Muscle aches and pains

Other serious side effects of naloxone have since been reported in patients after surgery, including:

  • Changes in blood pressure
  • Irregular heartbeat
  • Difficult or labored breathing
  • Pulmonary edema (fluid in the lungs)
  • Heart attack

These side effects occur most often in patients who have cardiovascular disorders (heart problems) or receive other drugs that have similar effects.

In addition, excessive doses of Narcan given to these patients eliminated pain relief from opioids.

Allergic reactions to naloxone are very rare. There have been no conclusive studies as to the effects of using this drug while pregnant or breastfeeding. It is unknown if Narcan passes into breast milk.

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Risks of Narcan

The main risk of opioid overdose is respiratory depression (slow and ineffective breathing). After the administration of Narcan, this should improve.

However, due to the duration of action of most opioids, the patient can relapse back into respiratory depression. This will continue until enough Narcan is given to reverse the overdose.

If someone is physically dependent on opioids, Narcan can induce acute opioid withdrawal symptoms, including:

  • Fever
  • Body aches
  • Tachycardia (fast heartbeat)
  • Nausea/vomiting
  • Abdominal cramps
  • Diarrhea
  • Runny nose/sneezing
  • Goosebumps
  • Restlessness
  • Irritability
  • Nervousness
  • Increased blood pressure
  • Sweating
  • Shivering/trembling
  • Weakness

Narcan is approved for use in infants and children to treat opioid overdoses. The dosing depends on body weight, ranging from 0.005 milligram/kilogram (mg/kg) to 0.01 mg/kg.

Unlike adults, Narcan’s action on children may be delayed or unpredictable. As such, children are monitored for at least 24 hours in case a relapse occurs.

In children and infants, Narcan can induce acute opioid withdrawal syndrome, which is described previously in this section.

However, this syndrome is life-threatening to infants less than four weeks old.

Symptoms include:

  • Excessive crying
  • Convulsions
  • Hyperactive reflexes

Narcan crosses the placenta, and administration to a mother dependent on opioids may result in withdrawal in the fetus. This can be life-threatening, and both the mother and fetus should be monitored closely after treatment.

Geriatric patients (ages 65 and older) are more likely to have decreased liver, kidney, and cardiac function.

Additionally, they may take more medication or develop other health conditions as a result of increased age. When these patients receive Narcan, it is metabolized differently compared to healthy adults, resulting in more exposure to the drug.

Narcan and Other Drugs

Buprenorphine is a medication that treats opioid use disorder. If someone who uses the drug has an opioid overdose, it will bind to and block the same receptors as Narcan.

Buprenorphine also has a longer duration of action and stays on receptors longer, stopping Narcan’s effects. As a result, treatment may need to be repeated multiple times to reverse the overdose.

Narcan and Addiction

Narcan has not been shown to be addictive. However, prescription opioids are classified as Schedule II drugs by the Drug Enforcement Administration.

These are defined as, “drugs with a high potential for abuse, with use potentially leading to severe psychological or physical dependence.” Along with this, they are considered highly dangerous.

Heroin is an illicit opioid classified as a Schedule I drug, with no currently accepted medical use and a high potential for abuse.

Signs of opioid addiction and abuse include:

  • Drowsiness
  • Changes in sleep patterns
  • Frequent flu-like symptoms
  • Changes in exercise habits
  • Money problems
  • Lack of hygiene
  • Weight loss
  • Decreased libido
  • Isolation from family or friends
  • Stealing from family, friends, or businesses
  • Associating with people who encourage addiction

Addiction is characterized by a set of behaviors surrounding drug use. Someone who is addicted to opioids might be unable to stop using them. Seek medical help if you or someone you know is experiencing addiction.

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Addiction Treatment Options

There are a wide variety of programs to treat opioid addiction and abuse.

Medication-assisted treatment (MAT) combines drugs such as buprenorphine, naltrexone, and methadone with therapy to provide a “whole patient” approach.

Aside from MAT, there are also various therapies.

These include:

These therapies can take place in an inpatient or outpatient setting.

Finally, there are various support groups out there. An example would be Narcotics Anonymous, a 12-step group modeled on Alcoholics Anonymous. There are also groups like SMART Recovery, which use alternative programs to the 12-step model.

Overcoming an opioid addiction is difficult to do alone. Speak with your healthcare provider for information on rehabilitation centers in your area and for medical advice when it comes time to detox.

Narcan FAQs

What is Narcan used to treat?

Narcan is used to treat an opioid overdose with symptoms of breathing problems, severe sleepiness, or inability to respond.

How is Narcan given?

Narcan (naloxone) can be administered via a nasal spray, or an injection subcutaneously (into the skin), intravenously (into the veins), or intramuscularly (into the muscles). Intravenously is the most rapid-acting method.

What happens after administering Narcan?

If someone is overdosing, the first step is to stimulate them awake by yelling their name and rubbing their sternum. Administer one dose of Narcan every two minutes. Call 911. Administer rescue breathing. The person should start breathing regularly on their own, then roll them into a recovery position on their side.

Can Narcan be used for heart attack?

No, naloxone has no role in the management of cardiac arrest. If a heart attack is a symptom of an opioid overdose, Narcan may help.

What drugs can Narcan counteract?

Narcan can help counteract opioid overdoses.

Common opioids include:


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  1. Cash, Rebecca E., Kinsman, Jeremiah, Crowe, Remle P., Rivard, Madison K., Faul, Mark, Panchal, Ashish R. “Naloxone Administration Frequency During Emergency Medical Service Events — United States, 2012-2016.” Morbidity and Mortality Weekly Report, US Department of Health and Human Services/Centers for Disease Control and Prevention, Aug. 2018.
  2. Centers for Disease Control and Prevention. “2018 Annual Surveillance Report of Drug-Related Risks and Outcomes.” CDC, Aug. 2018.
  3. Centers for Disease Control and Prevention. “Using Naloxone to Reverse Opioid Overdose in the Workplace: Information for Employers and Workers.” CDC, Oct. 2018.
  4. Drug Enforcement Administration. “Drug Scheduling.” DEA.
  5. Food and Drug Administration. “NARCAN (naloxone hydrochloride).” FDA, Nov. 2015.
  6. Johns Hopkins Medicine. “Signs of Opioid Abuse.” Johns Hopkins Medicine.
  7. MedlinePlus. “Opioid Misuse and Addiction Treatment.” MedlinePlus, Aug. 2018,
  8. National Institute on Drug Abuse. “Effective Treatments for Opioid Addiction.” NIDA, Nov. 2016,
  9. National Institute on Drug Abuse. “Naloxone.” NIDA, Sept. 2019.

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