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Nalmefene Side Effects

Medically reviewed by Last updated on Sep 26, 2023.

Applies to nalmefene: injection solution. Other dosage forms:

Serious side effects of Nalmefene

Along with its needed effects, nalmefene 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 or nurse immediately if any of the following side effects occur while taking nalmefene:

More common

  • Burred vision
  • dizziness
  • fast, pounding, or irregular heartbeat or pulse
  • headache
  • nervousness
  • pounding in the ears
  • slow or fast heartbeat

Less common

  • Confusion
  • dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • feeling of warmth or heat
  • flushing or redness of the skin, especially on the face and neck
  • sweating
  • unusual tiredness or weakness


  • Anxiety
  • chest pain or discomfort
  • discouragement
  • dry mouth
  • feeling sad or empty
  • hyperventilation
  • irritability
  • lack of appetite
  • loss of interest or pleasure
  • muscle twitching or jerking
  • rhythmic movement of the muscles
  • shaking
  • trouble breathing
  • trouble concentrating
  • trouble sleeping

Incidence not known

  • Blue lips or fingernails
  • coughing that sometimes produces a pink frothy sputum
  • difficulty, fast, or noisy breathing
  • pale skin
  • swelling in the legs and ankles

Other side effects of Nalmefene

Some side effects of nalmefene may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

Less common

  • Chills


  • Body aches or pain
  • cough
  • decrease in frequency of urination
  • decrease in urine volume
  • difficulty in passing urine
  • dryness or soreness of the throat
  • fever
  • itching skin
  • painful urination
  • stuffy or runny nose
  • swollen glands in the neck
  • trouble swallowing
  • voice changes

For Healthcare Professionals

Applies to nalmefene: injectable solution, nasal spray.


Gastrointestinal side effects have occurred commonly, with nausea and vomiting observed in 18% and 9%, respectively, of treated patients. Diarrhea and dry mouth have been reported in less than 1% of patients.[Ref]


Cardiovascular adverse effects including tachycardia, hypertension, hypotension, vasodilation, bradycardia, and arrhythmia have been reported in 5% or fewer of treated patients.[Ref]

Nervous system

Nervous system side effects including postoperative pain, dizziness, headache, fever, and chills have been reported in less than 5% of treated patients. Somnolence, depression, agitation, nervousness, tremor, confusion, and myoclonus have been reported in less than 1% of patients.[Ref]

Nalmefene administration may precipitate acute and extended withdrawal symptoms in opioid-dependent patients.[Ref]


A 21-year-old male with no significant past medical history had decreased respirations following an exploratory laparotomy for presumed appendicitis. The patient developed acute pulmonary edema after receiving 75 mcg nalmefene in 25 mcg increments over 10 minutes. Clinical resolution of symptoms was prompt after supplemental oxygen and furosemide. It took 36 hours for the chest X-ray to improve.[Ref]

Respiratory side effects have included pharyngitis (less than 1%). Pulmonary edema is an uncommon effect that has occurred with nalmefene administration.[Ref]


Dermatologic side effects have infrequently included pruritus (less than 1%).[Ref]


Genitourinary side effects have included rare reports of urinary retention (less than 1%).[Ref]


Other side effects including fever (3%) and chills (1%) have been reported.


1. Barsan WG, Seger D, Danzl DF, Ling LJ, Bartlett R, Buncher R, Bryan C. Duration of antagonistic effects of nalmefene and naloxone in opiate- induced sedation for emergency department procedures. Am J Emerg Med. 1989;7:155-61.

2. Product Information. Revex (nalmefene). OHMEDA. 2001.

3. Kaplan JL, Marx JA, Calabro JJ, GinShaw SL, Spiller JD, Spivey WL, Gaddis GM, Zhao N, Harchelroad FP. Double-blind, randomized study of nalmefene and naloxone in emergency department patients with suspected narcotic overdose. Ann Emerg Med. 1999;34:42-50.

4. Rosen DA, Morris JL, Rosen KR, et al. Nalmefene to prevent epidural narcotic side effects in pediatric patients: a pharmacokinetic and safety study. Pharmacotherapy. 2000;20:745-9.

5. Henderson CA, Reynolds JE. Acute pulmonary edema in a young male after intravenous nalmefene. Anesth Analg. 1997;84:218-9.

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.