Narcan Side Effects Center

Last updated on RxList: 10/12/2021
Narcan Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

What Is Narcan?

Narcan (naloxone) is an opioid antagonist used for the complete or partial reversal of opioid overdose, including respiratory depression. Narcan is also used for diagnosis of suspected or known acute opioid overdose and also for blood pressure support in septic shock. Narcan is available in generic form.

What Are Side Effects of Narcan?

Common side effects of Narcan and narcotic drug withdrawal are:

  • flushing,
  • dizziness,
  • tiredness,
  • weakness,
  • nervousness,
  • restlessness,
  • irritability,
  • body aches,
  • diarrhea,
  • stomach pain,
  • nausea,
  • fever,
  • chills,
  • goosebumps,
  • sneezing,
  • shortness of breath, or
  • runny nose.

Severe side effects of Narcan include:

Dosage for Narcan?

Narcan is available as a sterile solution for intravenous, intramuscular, and subcutaneous administration in three strengths: 0.02, 0.4 and 1 mg of naloxone hydrochloride per mL in sterile solution; the 0.4 and 1 mg doses are also available in multidose vials. Use in neonates and other pediatric patients is based on weight (usually 0.01 mg per Kg) and may be adjusted; a pediatric consultant may help manages such patients. Opioid withdrawal syndrome may occur in some patients given large doses of Narcan.

Narcan During Pregnancy and Breastfeeding

Studies on the use of this drug in pregnant and women who are breastfeeding have not been done. Tell your doctor if you are pregnant or breastfeeding.

Additional Information

Our Narcan Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

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.


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Narcan Consumer Information

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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 pain;
  • fever, sweating, body aches, weakness;
  • tremors or shivering, fast heart rate, pounding heartbeats, increased blood pressure;
  • goose bumps, shivering;
  • 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 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.

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.

Read the entire detailed patient monograph for Narcan (Naloxone Hydrochloride Injection)

Narcan Professional Information



The following adverse events have been associated with the use of NARCAN (naloxone) in postoperative patients: hypotension, hypertension, ventricular tachycardia and fibrillation, dyspnea, pulmonary edema, and cardiac arrest. Death, coma, and encephalopathy have been reported as sequelae of these events. Excessive doses of NARCAN (naloxone) in postoperative patients may result in significant reversal of analgesia and may cause agitation (see PRECAUTIONS and DOSAGE AND ADMINISTRATION; Usage in Adults-Postoperative Opioid Depression) Opioid Depression

Abrupt reversal of opioid depression may result in nausea, vomiting, sweating, tachycardia, increased blood pressure, tremulousness, seizures, ventricular tachycardia and fibrillation, pulmonary edema, and cardiac arrest which may result in death (see PRECAUTIONS).

Opioid Dependence

Abrupt reversal of opioid effects in persons who are physically dependent on opioids may precipitate an acute withdrawal syndrome which may include, but is not limited to, the following signs and symptoms: body aches, fever, sweating, runny nose, sneezing, piloerection, yawning, weakness, shivering or trembling, nervousness, restlessness or irritability, diarrhea, nausea or vomiting, abdominal cramps, increased blood pressure, tachycardia. In the neonate, opioid withdrawal may also include: convulsions; excessive crying; hyperactive reflexes (see WARNINGS).

Adverse events associated with the postoperative use of NARCAN (naloxone) are listed by organ system and in decreasing order of frequency as follows:

Cardiac Disorders: pulmonary edema, cardiac arrest or failure, tachycardia, ventricular fibrillation, and ventricular tachycardia. Death, coma, and encephalopathy have been reported as sequelae of these events.

Gastrointestinal Disorders: vomiting, nausea

Nervous System Disorders: convulsions, paresthesia, grand mal convulsion

Psychiatric Disorders: agitation, hallucination, tremulousness

Respiratory Thoracic and Mediastinal Disorders: dyspnea, respiratory depression, hypoxia

Skin and Subcutaneous Tissue Disorders: nonspecific injection site reactions, sweating

Vascular Disorders: hypertension, hypotension, hot flushes or flushing.

See also PRECAUTIONS and DOSAGE AND ADMINISTRATION; Usage in Adults; Postoperative Opioid Depression.

Drug Abuse And Dependence

NARCAN (naloxone) is an opioid antagonist. Physical dependence associated with the use of NARCAN (naloxone) has not been reported. Tolerance to the opioid antagonist effect of NARCAN (naloxone) is not known to occur.

Read the entire FDA prescribing information for Narcan (Naloxone Hydrochloride Injection)

© Narcan Patient Information is supplied by Cerner Multum, Inc. and Narcan Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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