Updated on February 6, 2024
4 min read

Narcan (Naloxone) How Does It Work?

What is Narcan?

Narcan is a nasal spray treatment that reverses the effects of opioid overdoses. It is used to counteract the effects of opioid overdose.

The name 'Narcan' refers to a specific formulation of the generic drug naloxone. Naloxone is an opioid antagonist that binds to and blocks opioid receptors. 

Symptoms of an opioid overdose include:

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

Naloxone Availability 

Naloxone is typically available over the counter (OTC). The Food and Drug Administration (FDA) has approved three forms of the drug:

  1. Nasal spray (Narcan)
  2. Injectable
  3. Auto-injectable (Evzio)

All three forms are highly effective at reversing an overdose. Narcan nasal spray is easier for families, caregivers, and non-medical personnel to administer. The ease of use makes 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)

How is Narcan Used?

There are four ways to administer Narcan.

  • Nasal spray
  • Injection
  • Intravenously
  • Intramuscularly

To administer Narcan nasally, lay the patient flat on their back. When ready, spray into the nostril once. Support their neck and let the head tip back to ensure the drug enters the body.

What Should You Do After the First Dose?

Following dosing, contact emergency medical services (EMS) immediately. Overdoses are life-threatening and require immediate medical attention.

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

Each naloxone nasal spray contains a single dose, which you can only use once. Use a new tube every two to three minutes, alternating nostrils.


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Side Effects of Narcan

Potential side effects of Narcan 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 heart problems. It can also happen to people taking other drugs with similar effects.

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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 an opioid overdose, respiratory depression can happen again. The depression will continue until enough Narcan is given to reverse the overdose.

Acute opioid withdrawal symptoms can emerge in people dependent on opioids. Opioid withdrawal symptoms include:

  • 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

Risks of Narcan for Children and Infants

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

Unlike adults, Narcan’s action on children may be delayed or unpredictable. Adults should monitor children for at least 24 hours in case a relapse occurs.

Narcan can also induce acute opioid withdrawal syndrome in children and infants. This syndrome is life-threatening to infants less than four weeks old.

Symptoms include:

  • Excessive crying
  • Convulsions
  • Hyperactive reflexes

Other Potential Risks

Narcan can be dangerous for a pregnant mother and her fetus. Narcan crosses the placenta, and administration to a mother may result in withdrawal in the fetus. 

Withdrawal can be life-threatening. Both the mother and fetus should be monitored closely after treatment.

Narcan can also develop health conditions in geriatric patients. Due to their age, they metabolize Narcan differently than younger adults. They may get more exposure to the drug because of their metabolism.

Narcan and Other Drugs

Buprenorphine is a medication that helps 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

There is little to no evidence that shows that Narcan is addictive. However, prescription opioids are classified as Schedule II drugs by the Drug Enforcement Administration.

The DEA defines Narcan 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.

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Addiction Treatment Options

There are a wide variety of programs to treat opioid addiction and abuse. These include therapies and treatments such as:

Overcoming an opioid addiction is difficult to do alone. Speak with your healthcare provider for medical help and information on rehabilitation centers in your area.

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Updated on February 6, 2024
9 sources cited
Updated on February 6, 2024
  1. Cash, et al.“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, 2018.
  2. Centers for Disease Control and Prevention. “2018 Annual Surveillance Report of Drug-Related Risks and Outcomes.” CDC, 2018.
  3. Centers for Disease Control and Prevention. “Using Naloxone to Reverse Opioid Overdose in the Workplace: Information for Employers and Workers.” CDC, 2018.
  4. Drug Enforcement Administration. “Drug Scheduling.” DEA.
  5. Food and Drug Administration. “NARCAN (naloxone hydrochloride).” FDA, 2015.
  6. Johns Hopkins Medicine. “Signs of Opioid Abuse.” Johns Hopkins Medicine.
  7. MedlinePlus. “Opioid Misuse and Addiction Treatment.” MedlinePlus, 2018.
  8. National Institute on Drug Abuse. “Effective Treatments for Opioid Addiction.” NIDA, 2016.
  9. National Institute on Drug Abuse. “Naloxone.” NIDA,  2019.

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