Skip to main content

Narcan Injection Side Effects

Generic name: naloxone

Medically reviewed by Last updated on Mar 28, 2024.

Note: This document contains side effect information about naloxone. Some dosage forms listed on this page may not apply to the brand name Narcan Injection.

Applies to naloxone: injection solution. Other dosage forms:

Serious side effects of Narcan Injection

Along with its needed effects, naloxone (the active ingredient contained in Narcan Injection) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking naloxone:

Incidence not known

For Healthcare Professionals

Applies to naloxone: compounding powder, injectable kit, injectable solution, nasal spray, oral solution.


This drug may precipitate abrupt opioid withdrawal in physically dependent persons; signs and symptoms may include body aches, fever, sweating, sneezing, yawning, nausea, vomiting, sweating, lacrimation, rhinorrhea, cramping, insomnia, chills/hot flashes, piloerection, tachycardia, anxiety, restlessness, irritability, tremulousness, hypertension, seizures, and cardiac arrest. In the neonate, opioid withdrawal may also include convulsions, excessive crying, and hyperactive reflexes.[Ref]


Common (1% to 10%): Tachycardia, hypotension, hypertension

Uncommon (0.1% to 1%): Arrhythmia, bradycardia

Rare (less than 0.1%): Fibrillation, cardiac arrest

Frequency not reported: Left ventricular failure, flushing[Ref]

In postoperative patients, many of whom had cardiovascular disease, the following cardiovascular side effects have been reported: hypotension, hypertension, atrial and ventricular tachycardia, ventricular fibrillation, left ventricular failure, and cardiac arrest. Death, coma, and encephalopathy have been reported as sequelae of these events.[Ref]

Nervous system

Common (1% to 10%): Dizziness, headache

Uncommon (0.1% to 1%): Tremor

Rare (less than 0.1%): Seizures

Frequency not reported: Coma, encephalopathy, convulsions, paraesthesia, grand mal convulsion[Ref]

Death, coma, and encephalopathy have been reported as a result of abrupt postoperative reversal of opioid depression, primarily in patients with preexisting cardiovascular disorders or in those who received other drugs with similar adverse cardiovascular effects.[Ref]


Very rare (less than 0.01%): Pulmonary edema

Frequency not reported: Dyspnea, respiratory depression, hypoxia, nasal dryness, nasal edema, nasal congestion, nasal inflammation[Ref]

It has been suggested that pulmonary edema may be due to a centrally mediated massive catecholamine response leading to a dramatic shift of blood volume into the pulmonary vascular bed resulting in increased hydrostatic pressures.

Nasal dryness, nasal edema, nasal congestion, and nasal inflammation were the most common adverse reactions reported in clinical trials with naloxone nasal spray.[Ref]


Frequency not reported: Nonspecific injection site reactions, irritation of vessel was after IV administration[Ref]


Common (1% to 10%): Nausea, vomiting

Uncommon (0.1% to 1%): Diarrhea, dry mouth[Ref]


Very rare (less than 0.01%): Erythema multiforme

Frequency not reported: Sweating[Ref]


Very rare (less than 0.01%): Allergic reactions including urticaria, rhinitis, dyspnea, Quincke's edema, anaphylactic shock[Ref]


Frequency not reported: Agitation, hallucination, tremulousness[Ref]


Frequency not reported: Musculoskeletal pain[Ref]

Musculoskeletal pain was one of the more commonly reported adverse reactions in clinical trials with naloxone nasal spray.[Ref]

Frequently asked questions


1. Product Information. Narcan (naloxone). DuPont Pharmaceuticals. 2001;PROD.

2. Cerner Multum, Inc. UK Summary of Product Characteristics.

3. Cerner Multum, Inc. Australian Product Information.

Further information

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

Some side effects may not be reported. You may report them to the FDA.