Allopurinol Side Effects

Medically reviewed by Drugs.com. Last updated on Jun 3, 2024.

Applies to allopurinol: intravenous powder for solution.

Other dosage forms:

• oral tablet

Serious side effects of allopurinol

Along with its needed effects, allopurinol 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 allopurinol:

Less common side effects

• agitation
• coma
• confusion
• decreased urine output
• depression
• dizziness
• headache
• hostility
• irritability
• lethargy
• muscle twitching
• nausea
• rapid weight gain
• seizures
• stupor
• swelling of the face, ankles, or hands
• unusual tiredness or weakness

Rare side effects

• black, tarry stools
• bladder pain
• bleeding gums
• blistering, peeling, loosening of the skin
• blood in the urine or stools
• blurred vision
• changes in skin color
• chest pain or tightness
• chills
• clay-colored stools
• cloudy urine
• cough or hoarseness
• coughing up blood
• dark urine
• diarrhea
• difficult, burning, or painful urination
• difficulty with breathing or swallowing
• difficulty with speaking
• dilated neck veins
• dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
• double vision
• enlarged stomach
• fainting
• fast or slow heartbeat
• feeling of warmth
• fever
• frequent urge to urinate
• inability to move the arms, legs, or facial muscles
• inability to speak
• increased menstrual flow or vaginal bleeding
• increased sweating
• irregular breathing
• irregular heartbeat
• itching, rash
• joint pain, stiffness, or swelling
• lightheadedness
• loosening of the fingernails
• loss of appetite
• loss of strength or energy
• lower back or side pain
• muscle pain or weakness
• nosebleeds
• numbness, tingling, pain, or weakness in the hands or feet
• pain, tenderness, or swelling of the foot or leg
• painful or difficult urination
• paralysis
• pinpoint red spots on the skin
• prolonged bleeding from cuts
• rapid, shallow breathing
• red or black, tarry stools
• red or dark brown urine
• red skin lesions, often with a purple center
• redness of the face, neck, arms, and occasionally, upper chest
• slow speech
• sore throat
• sores, ulcers, or white spots on the lips or in the mouth
• stomach pain
• sweating
• swelling of the fingers, feet, or lower legs
• swollen glands
• trouble breathing
• unpleasant breath odor
• unusual bleeding or bruising
• unusual weak feeling
• vomiting of blood
• weight gain
• yellow eyes or skin

Other side effects of allopurinol

Some side effects of allopurinol 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:

Less common side effects

• drowsiness
• indigestion
• unusual hair loss

Rare side effects

• bleeding, blistering, burning, coldness, discoloration of the skin, feeling of pressure, hives, infection, inflammation, itching, lumps, numbness, pain, rash, redness, scarring, soreness, stinging, swelling, tenderness, tingling, ulceration, or warmth at the injection site
• body aches or pain
• congestion
• cracked lips
• difficulty with moving
• hair loss or thinning of the hair
• hives or welts
• muscle stiffness
• pain, redness, swelling, tenderness, or warmth on the skin
• runny nose
• voice changes

For healthcare professionals

Applies to allopurinol: intravenous powder for injection, oral tablet.

General adverse events

The most commonly reported adverse reactions include skin rash, diarrhea, nausea, alkaline phosphatase, and transaminase elevation.^[Ref]

Dermatologic

• Common (1% to 10%): Rash, maculopapular rash
• Uncommon (0.1% to 1%): Ecchymosis
• Rare (less than 0.1%): Steven-Johnson syndrome, Lyell syndrome
• Very rare (less than 0.01%): Alopecia, discolored hair, angioedema, fixed drug eruption
• Frequency not reported: DRESS (Drug reaction with eosinophilia and systemic symptoms), sweating^[Ref]

Skin rash is one of the most common adverse reactions and may occur at any time during treatment. Some skin reactions can be severe and sometimes fatal. In patients with the most severe reactions, systemic symptoms such as fever, chills, arthralgia, cholestatic jaundice, eosinophilia and mild leukocytosis, or leukopenia accompany the rash. Among 55 patients with gout who received this drug for an average of 1 year (3 to 34 months), 3% developed pruritic maculopapular skin eruptions, sometimes scaly or exfoliative. The incidence of skin rash appears to be greater in patients with renal insufficiency.

Angioedema has been reported with and without signs and symptoms of a more generalized hypersensitivity reaction. Skin reactions associated with exfoliation, fever, lymphadenopathy, arthralgia, and/or eosinophilia resembling Stevens-Johnson and/or Lyell syndromes have occurred rarely. Associated vasculitis and tissue responses may manifest as hepatitis, interstitial nephritis, and very rarely epilepsy.

DRESS also known as drug hypersensitivity syndrome has been reported. The syndrome is potentially life-threatening and fatal. It has been reported that symptoms may develop in approximately 1 week from initiating allopurinol therapy, but longer latency periods have also been reported.^[Ref]

Hypersensitivity

• Rare (less than 0.1%): Generalized hypersensitivity
• Very rare (less than 0.01%): Anaphylaxis, angioedema
• Frequency not reported: Hypersensitivity reaction^[Ref]

Generalized hypersensitivity including skin reactions associated with exfoliation, fever, lymphadenopathy, arthralgia, and/or eosinophilia resembling Stevens-Johnson and/or Lyell syndromes have occurred rarely. Associated vasculitis and tissue responses may manifest as hepatitis, interstitial nephritis, and very rarely epilepsy. When generalized hypersensitivity reactions have occurred, renal and or/hepatic disorders have often been present, particularly when the outcome has been fatal.

Angioedema has been reported with and without signs and symptoms of a more generalized hypersensitivity reaction.^[Ref]

Hepatic

• Common (1% to 10%): Increases in alkaline phosphatase and serum transaminases
• Rare (less than 0.1%): Hepatic dysfunction including hepatitis (hepatic necrosis and granulomatous hepatitis), hepatomegaly, cholestatic jaundice,
• Frequency not reported: Clinical hepatotoxicity, liver failure^[Ref]

Liver failure was reported in less than 1% of patients.^[Ref]

Gastrointestinal

• Common (1% to 10%): Diarrhea, nausea, vomiting
• Rare (less than 0.1%): Intermittent abdominal pain, gastritis, dyspepsia
• Very rare (less than 0.01%): Steatorrhea, recurrent hematemesis, stomatitis, changed bowel habit
• Frequency not reported: Hemorrhagic pancreatitis, gastrointestinal bleeding, salivary gland swelling, tongue edema, anorexia, flatulence^[Ref]

Hemorrhagic pancreatitis, gastrointestinal bleeding, salivary gland swelling, tongue edema, flatulence, and anorexia were reported in less than 1% of patients.^[Ref]

Hematologic

• Very rare (less than 0.01%): Leukocytosis, leukopenia, eosinophilia, thrombocytopenia, granulocytopenia, agranulocytosis, aplastic anemia
• Frequency not reported: Bone marrow depression, eosinophilic fibrohistiocytic lesion of bone marrow, pancytopenia, anemia, hemolytic anemia, reticulocytosis, lymphadenopathy, lymphocytosis, disseminated intravascular coagulation^[Ref]

Eosinophilic fibrohistiocytic lesion of bone marrow, pancytopenia, anemia, hemolytic anemia, reticulocytosis, lymphadenopathy, disseminated intravascular coagulation, and lymphocytosis were reported in less than 1% of patients.^[Ref]

Renal

• Common (1% to 10%): Renal failure/insufficiency
• Very rare (less than 0.01%): Xanthine crystalluria, azotemia^[Ref]

Xanthine crystalluria has been reported in 3 patients; 2 patients with Lesch-Nyhan syndrome and 1 patient with lymphosarcoma who produced an extremely large amount of uric acid during chemotherapy.

Increased serum creatinine and kidney function abnormality has been reported in less than 1% of patients.^[Ref]

Nervous system

• Uncommon (0.1% to 1%): Headache
• Very rare (less than 0.01%): Ataxia, somnolence, coma, paralysis, paresthesia, neuropathy, taste perversion, neuritis
• Frequency not reported: Drowsiness, confusion, foot drop, seizure, status epilepticus, myoclonus, twitching, cerebral infarction, stroke, tremor^[Ref]

Confusion, foot drop, seizure, status epilepticus, myoclonus, twitching, cerebral infarction, stroke, and tremor were reported in less than 1% of patients.^[Ref]

Ocular

• Very rare (less than 0.01%): Visual disorder, cataract, macular changes
• Frequency not reported: Optic neuritis^[Ref]

Immunologic

• Very rare (less than 0.01%): Furunculosis, angioimmunoblastic lymphadenopathy^[Ref]

Metabolic

• Uncommon (0.1% to 1%): Increase in acute gout attacks
• Very rare (less than 0.01%): Diabetes mellitus, hyperlipidemia
• Frequency not reported: Hypercalcemia, hypocalcemia, hyperphosphatemia, hypokalemia, hyperuricemia, electrolyte abnormality, hyperglycemia, hypernatremia, metabolic acidosis, glycosuria, hyperkalemia, lactic acidosis, water intoxication, hypomagnesemia^[Ref]

Early clinical experience with this drug found acute gouty attacks on therapy initiation to be one of the more commonly observed adverse reactions; however, current use analyses suggests this incidence is now less than 1%. The reason for this change has not been determined, but it may be due to patients initiating therapy more gradually.

Hypercalcemia, hypocalcemia, hyperphosphatemia, hypokalemia, hyperuricemia, electrolyte abnormality, hyperglycemia, hypernatremia, metabolic acidosis, glycosuria, hyperkalemia, lactic acidosis, water intoxication, and hypomagnesemia have been reported in less than 1% of patients.^[Ref]

Musculoskeletal

• Rare (less than 0.1%): Myopathy, arthralgias^[Ref]

Cardiovascular

• Uncommon (0.1% to 1%): Necrotizing angiitis, vasculitis, edema
• Very rare (less than 0.01%): Angina, bradycardia, hypertension
• Frequency not reported: Pericarditis, peripheral vascular disease thrombophlebitis, vasodilation, heart failure, cardiorespiratory arrest, decreased venous pressure, flushing, cardiovascular disorder, ECG abnormality, hemorrhage, ventricular fibrillation^[Ref]

Pericarditis, peripheral vascular disease thrombophlebitis, vasodilation, heart failure, cardiorespiratory arrest, decreased venous pressure, flushing, cardiovascular disorder, ECG abnormality, hemorrhage, and ventricular fibrillation were reported in less than 1% of patients.^[Ref]

Endocrine

• Uncommon (0.1% to 1%): Gynecomastia^[Ref]

Genitourinary

• Uncommon (0.1% to 1%): Infertility, impotence, nocturnal emission
• Very rare (less than 0.01%): Uremia, hematuria, male infertility, impotence, erectile dysfunction
• Frequency not reported: Urinary tract infection^[Ref]

Local

• Frequency not reported: Injection site reactions^[Ref]

Injection site reactions have been reported with the parenteral product in less than 1% of patients.^[Ref]

Other

• Uncommon (0.1% to 1%): Fever, general malaise, asthenia
• Very rare (less than 0.01%): Vertigo
• Frequency not reported: Tinnitus^[Ref]

Psychiatric

• Very rare (less than 0.01%): Depression
• Frequency not reported: Amnesia, insomnia, agitation^[Ref]

Amnesia, agitation, and insomnia were reported in less than 1% of patients.^[Ref]

Respiratory

• Rare (less than 0.1%): Epistaxis
• Frequency not reported: Bronchospasm, asthma, pharyngitis, rhinitis, respiratory failure/insufficiency, ARDS, increased respiration rate, apnea^[Ref]

Bronchospasm, asthma, pharyngitis, respiratory failure/insufficiency, ARDS, increased respiration rate, apnea, and rhinitis were reported in less than 1% of patients.^[Ref]

Further information

Allopurinol side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer