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Naltrexone Side Effects

Medically reviewed by Last updated on Apr 16, 2022.

In Summary

Commonly reported side effects of naltrexone include: streptococcal pharyngitis, syncope, anxiety, arthralgia, arthritis, dizziness, drowsiness, fatigue, frequent headaches, headache, joint stiffness, nasopharyngitis, nausea, nervousness, obsessive compulsive disorder, panic attack, pharyngitis, posttraumatic stress disorder, sedated state, sinus headache, vomiting, induration at injection site, malaise, pain at injection site, and tenderness at injection site. Other side effects include: muscle cramps, muscle rigidity, muscle spasm, stiffness, depression, and twitching. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to naltrexone: oral tablet

Other dosage forms:

Side effects requiring immediate medical attention

Along with its needed effects, naltrexone 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 naltrexone:

Less common


  • Abdominal or stomach pain (severe)
  • blurred vision, aching, burning, or swollen eyes
  • chest pain
  • confusion
  • discomfort while urinating or frequent urination
  • fever
  • hallucinations or seeing, hearing, or feeling things that are not there
  • itching
  • mental depression or other mood or mental changes
  • ringing or buzzing in the ears
  • shortness of breath
  • swelling of the face, feet, or lower legs
  • weight gain

Side effects not requiring immediate medical attention

Some side effects of naltrexone 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
  • constipation
  • cough, hoarseness, runny or stuffy nose, sinus problems, sneezing, or sore throat
  • diarrhea
  • dizziness
  • fast or pounding heartbeat
  • increased thirst
  • irritability
  • loss of appetite
  • sexual problems in males

For Healthcare Professionals

Applies to naltrexone: compounding powder, intramuscular powder for injection extended release, oral tablet

Nervous system

Very common (10% or more): Headache (25%), dizziness/syncope (13%)

Common (1% to 10%): Somnolence/sedation

Frequency not reported: Lethargy, cerebral arterial aneurysm, convulsions, disturbance in attention, dysgeusia, mental impairment, migraine, ischemic stroke, paresthesia[Ref]


Very common (10% or more): Insomnia/sleep disorder (14%), anxiety (12%)

Common (1% to 10%): Depression

Uncommon (0.1% to 1%): Suicide attempt/ideation

Frequency not reported: Irritability, abnormal dreams, agitation, alcohol withdrawal syndrome, euphoric mood, delirium, libido decreased[Ref]


Very common (10% or more): Nausea (33%), vomiting NOS (14%), diarrhea (13%), abdominal pain (11%)

Common (1% to 10%): Dry mouth, toothache

Frequency not reported: Abdominal discomfort, colitis, constipation, flatulence, gastroesophageal reflux disease, gastrointestinal hemorrhage, hemorrhoids, pancreatitis acute, paralytic ileus[Ref]


Very common (10% or more): Alanine aminotransferase increased (13%), aspartate aminotransferase increased (10%)

Common (1% to 10%): Gamma-glutamyltransferase increased

Frequency not reported: Lymphadenopathy including cervical adenitis, white blood cell count increased, cholecystitis acute, cholelithiasis[Ref]


Very common (10% or more): Injection site tenderness (45%), injection site induration (35%), injection site pain (17%), other injection site reaction (primarily nodules, swelling) (15%), injection site pruritus (10%)

Common (1% to 10%): Injection site ecchymosis[Ref]


Very common (10% or more): Arthralgia/arthritis/joint stiffness (12%)

Common (1% to 10%): Back pain/stiffness, muscle cramps

Frequency not reported: Chills, joint stiffness, muscle spasms, myalgia, pain in limb[Ref]


Very common (10% or more): Asthenic conditions (23%)

Frequency not reported: Chest pain, chest tightness, abortion missed[Ref]


Frequency not reported: Angina pectoris, angina unstable, atrial fibrillation, cardiac failure congestive, coronary artery atherosclerosis, myocardial infarction, palpitations, deep vein thrombosis[Ref]


Frequency not reported: Chronic obstructive pulmonary disease, dyspnea, pharyngolaryngeal pain, sinus congestion[Ref]


Common (1% to 10%): Rash

Frequency not reported: Face edema, night sweats, pruritus, sweating increased[Ref]


Very common (10% or more): Anorexia/appetite decreased NOS/appetite disorder NOS (14%)

Frequency not reported: Weight decreased, weight increased, appetite increased, dehydration[Ref]


Very common (10% or more): Abnormal creatinine phosphokinase levels (17%)[Ref]


Frequency not reported: Eosinophil counts increased, decreased platelet count[Ref]


Frequency not reported: Conjunctivitis, vision blurred[Ref]


Frequency not reported: Hypersensitivity reaction (including angioneurotic edema and urticaria)

Postmarketing reports: Anaphylaxis[Ref]


Very common (10% or more): Pharyngitis (11%)

Common (1% to 10%): Nasopharyngitis

Frequency not reported: Seasonal allergies[Ref]

Frequently asked questions


1. "Product Information. Vivitrol (naltrexone)." Alkermes, Inc, Cambridge, MA.

2. "Product Information. Naltrexone Hydrochloride (naltrexone)." Accord Biopharma Inc, Durham, NC.

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.