Allopurinol Side Effects

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

Applies to allopurinol: oral tablet.

Other dosage forms:

• intravenous powder for solution

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 immediately if any of the following side effects occur while taking allopurinol:

More common side effects

• ankle, knee, or great toe joint pain
• joint stiffness or swelling
• rash
• rash with flat lesions or small raised lesions on the skin

Rare side effects

• agitation
• ammonia-like breath odor
• anxiety
• bleeding gums
• blistering, peeling, or loosening of the skin
• blood in the urine or stools
• bloody nose
• bloody or black, tarry stools
• blue or pale skin
• bruising
• changes in skin color
• chest pain, tightness, or discomfort
• chest pain, possibly moving to the left arm, neck, or shoulder
• chills
• clay-colored stools
• cloudy urine
• confusion
• constipation
• cough
• coughing up blood
• cracks in the skin
• dark urine
• decreased awareness or responsiveness
• decreased urine output
• depression
• diarrhea
• difficulty with breathing
• dizziness
• drowsiness
• dry mouth
• feeling of warmth or heat
• fever
• flushing or redness of the skin, especially on the face and neck
• general feeling of discomfort or illness
• headache
• hives or welts, itching, skin rash
• hoarseness
• hostility
• incoherent speech
• increased urination
• irritability
• joint or muscle pain
• large, flat, blue or purplish patches in the skin
• light-colored stools
• loss of appetite
• loss of consciousness
• loss of heat from the body
• lower back or side pain
• metallic taste
• muscle twitching or weakness
• nausea
• noisy breathing
• pain, tenderness, or swelling of the foot or leg
• painful or difficult urination
• pinpoint red or purple spots on the skin
• rapid weight gain
• red, irritated eyes
• red, swollen skin
• redness, soreness, or itching skin
• right upper abdominal or stomach pain and fullness
• scaly skin
• seizures
• severe sleepiness
• severe stomach pain
• slow or irregular heartbeat
• sore throat
• sores, ulcers, or white spots on the lips or in the mouth
• sores, welting, or blisters
• stomach pain
• sweating
• swelling of the face, ankles, hands, or lower legs
• swollen or painful glands
• swollen, painful, or tender lymph glands in the neck, armpit, or groin
• thirst
• unpleasant breath odor
• unusual bleeding or bruising
• unusual drowsiness, dullness, tiredness, weakness, or feeling of sluggishness
• unusual weight gain or loss
• vomiting
• vomiting of blood or material that looks like coffee grounds
• 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:

Rare side effects

• bad, unusual, or unpleasant (after) taste
• blindness
• blue-yellow color blindness
• blurred vision
• body aches or pain
• burning feeling in the chest or stomach
• burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
• burning, dry, or itching eyes
• change in taste
• change in vision
• congestion
• continuing ringing or buzzing or other unexplained noise in the ears
• decreased interest in sexual intercourse
• decreased vision
• difficulty with moving
• discharge or excessive tearing
• feeling of constant movement of self or surroundings
• hair loss or thinning of the hair
• hearing loss
• impaired vision
• inability to have or keep an erection
• indigestion
• lack or loss of strength
• loss in sexual ability, desire, drive, or performance
• loss of appetite
• loss of memory
• multiple swollen and inflamed skin lesions
• muscle pain, cramps, stiffness, tenderness, or wasting
• problems with memory
• redness, pain, or swelling of the eye, eyelid, or inner lining of the eyelid
• runny nose
• sensation of spinning
• sensitivity to light
• sleepiness or unusual drowsiness
• sleeplessness
• sneezing
• stomach upset
• stuffy nose
• sweating
• swelling of the breasts or breast soreness in both females and males
• swelling of the salivary glands
• swelling or inflammation of the mouth
• tearing
• tender, swollen glands in the neck
• tenderness in the stomach area
• throbbing pain
• trouble getting pregnant
• trouble with sleeping
• trouble with swallowing
• unsteadiness or awkwardness
• voice changes
• weakness in the arms, hands, legs, or feet
• weight loss

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.

Some side effects may not be reported. You may report them to the FDA.

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