Naltrexone Side Effects

Medically reviewed by Philip Thornton, DipPharm. Last updated on Sep 23, 2023.

Applies to naltrexone: oral capsule, oral tablet. Other dosage forms:

• intramuscular powder for suspension extended release

Serious side effects of Naltrexone

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

• Skin rash

Rare

• 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

Other side effects of Naltrexone

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

• Abdominal or stomach cramping or pain (mild or moderate)
• anxiety, nervousness, restlessness or trouble sleeping
• headache
• joint or muscle pain
• nausea or vomiting
• unusual tiredness

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 capsule, 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]

Psychiatric

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]

Gastrointestinal

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]

Hepatic

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]

Local

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]

Musculoskeletal

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]

Other

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

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

Cardiovascular

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

Respiratory

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

Dermatologic

Common (1% to 10%): Rash

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

Metabolic

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

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

Renal

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

Hematologic

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

Ocular

Frequency not reported: Conjunctivitis, vision blurred^[Ref]

Hypersensitivity

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

Postmarketing reports: Anaphylaxis^[Ref]

Immunologic

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

Common (1% to 10%): Nasopharyngitis

Frequency not reported: Seasonal allergies^[Ref]

Frequently asked questions

• What is low dose naltrexone (LDN)?
• What happens if you drink alcohol while taking naltrexone?
• What to avoid when taking naltrexone?
• Should I take naltrexone in the morning or at night?
• Does naltrexone cause weight gain?
• Acamprosate vs naltrexone: How do they compare?
• How does naltrexone make you feel?
• How long does naltrexone take to work?
• What is the mechanism of action for naltrexone?

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.

Medical Disclaimer