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Naloxone Side Effects

For the Consumer

Applies to naloxone: injection solution

As well as its needed effects, naloxone may cause unwanted side effects that require medical attention.

Major Side Effects

If any of the following side effects occur while taking naloxone, check with your doctor immediately:

Incidence not known:
  • Abdominal or stomach cramps
  • body aches
  • convulsions
  • diarrhea
  • difficult or troubled breathing
  • excessive crying
  • fast, pounding, or irregular heartbeat or pulse
  • fever
  • goosebumps
  • increased blood pressure
  • increased or excessive unconscious or jerking movements
  • irregular, fast or slow, or shallow breathing
  • irritability
  • nausea or vomiting
  • nervousness
  • pale or blue lips, fingernails, or skin
  • restlessness
  • runny nose
  • shivering
  • sneezing
  • sweating
  • trembling
  • weakness
  • yawning

For Healthcare Professionals

Applies to naloxone: compounding powder, injectable solution, nasal spray


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]


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]

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]

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]


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

Frequency not reported: Musculoskeletal pain[Ref]


1. "Product Information. Narcan (naloxone)." DuPont Pharmaceuticals, Wilmington, DE.

2. Cerner Multum, Inc. "Australian Product Information." O 0

3. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

It is possible that some side effects of naloxone may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.