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Allopurinol Side Effects

More frequently reported side effects include acute gout attack. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to allopurinol: oral capsule, oral tablet

In addition to its needed effects, some unwanted effects may be caused by allopurinol. In the event that any of these side effects do occur, they may require medical attention.

You should check with your doctor immediately if any of these side effects occur when taking allopurinol:

More common
  • Ankle, knee, or great toe joint pain
  • joint stiffness or swelling
  • rash
  • rash with flat lesions or small raised lesions on the skin
  • Abdominal or stomach pain
  • 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 or discomfort
  • chest pain, possibly moving to the left arm, neck, or shoulder
  • chills
  • clay-colored stools
  • cloudy urine
  • coma
  • confusion
  • constipation
  • cough or hoarseness
  • coughing up blood
  • cracks in the skin
  • dark urine
  • decreased urine output
  • depression
  • diarrhea
  • difficulty with breathing
  • dizziness
  • drowsiness
  • dry mouth
  • feeling faint, dizzy, or lightheaded
  • feeling of warmth or heat
  • fever
  • fever with or without chills
  • flushing or redness of the skin, especially on the face and neck
  • general feeling of discomfort or illness
  • general feeling of tiredness or weakness
  • headache
  • hostility
  • incoherent speech
  • increased urination
  • irritability
  • itching
  • joint or muscle pain
  • large, flat, blue or purplish patches in the skin
  • lethargy
  • light-colored stools
  • loss of appetite
  • loss of heat from the body
  • lower back or side pain
  • metallic taste
  • muscle twitching
  • muscle weakness
  • nausea or vomiting
  • pain, tenderness, or swelling of the foot or leg
  • painful or difficult urination
  • pinpoint red or purple spots on the skin
  • rapid weight gain
  • rash
  • red, irritated eyes
  • red, swollen skin
  • redness, soreness, or itching skin
  • right upper abdominal or stomach pain and fullness
  • scaly skin
  • seizures
  • severe stomach pain
  • shortness of breath
  • slow or irregular heartbeat
  • sore throat
  • sores, ulcers, or white spots on the lips or in the mouth
  • sores, welting, or blisters
  • stupor
  • 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
  • tightness in the chest
  • unpleasant breath odor
  • unusual bleeding or bruising
  • unusual weight gain or loss
  • vomiting of blood or material that looks like coffee grounds
  • wheezing
  • yellow eyes or skin

Some of the side effects that can occur with allopurinol may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

  • 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
  • burning, numbness, tingling, or painful sensations
  • 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
  • hives or welts
  • 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 aching or cramping
  • muscle pain or stiffness
  • muscular pain, tenderness, wasting, or weakness
  • noisy breathing
  • 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
  • swollen joints
  • tearing
  • tender, swollen glands in the neck
  • tenderness in the stomach area
  • throbbing pain
  • tightness in the chest
  • trouble getting pregnant
  • trouble with sleeping
  • trouble with swallowing
  • unable to sleep
  • 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


In general, the side effects of allopurinol have been more likely and more severe in patients with reduced renal function.[Ref]


Allopurinol-induced rash may be followed by more severe hypersensitivity reactions, including Stevens-Johnson syndrome, toxic epidermal necrolysis, vasculitis, nephrotoxicity, and hepatotoxicity. Such hypersensitivity syndromes have been fatal in some cases.

The incidence of skin rash may be increased in patients with renal dysfunction.[Ref]

Dermatologic side effects have included skin rash, pruritus, and alopecia. Severe skin reactions have rarely included exfoliative dermatitis, vesicular bullous eruptions, and erythema multiforme.[Ref]


A case study suggests cell-mediated immunity to allopurinol and oxypurinol is involved in allopurinol-induced hypersensitivity reactions.

A first of a kind case report, allopurinol hypersensitivity syndrome, elevations in pancreatic exocrine enzyme level, and new-onset type 1 diabetes mellitus have been reported in a 58-year-old Cambodian female.

Allopurinol-induced hypersensitivity reactions tend to occur more often in the presence of renal insufficiency and/or concomitant thiazide diuretic therapy.[Ref]

Hypersensitivity side effects have included hypersensitivity maculopapular rash (1% to 3%). Rash, eosinophilia, and fever have been reported in 0.3% of patients. Rare, but potentially fatal, reactions have included arthralgias, hepatitis, acute interstitial nephritis, vasculitis, and severe skin reactions. Stevens-Johnson syndrome, toxic epidermal necrolysis, and toxic pustuloderma have been reported rarely. At least 3 cases of allopurinol hypersensitivity syndrome have also been reported.[Ref]


Hypersensitivity appears to play a role in allopurinol-induced hepatotoxicity. Hepatitis is usually accompanied by fever, rash, and occasionally hepatomegaly. Liver biopsies in cases of hepatitis have revealed mild portal inflammation and acute centrilobular necrosis, consistent with hypersensitivity reactions.[Ref]

Hepatic side effects have included elevations in serum transaminases and alkaline phosphatase. Cholestatic jaundice, hepatic necrosis, granulomatous hepatitis, and hepatomegaly have been reported rarely.[Ref]


A first of a kind case report, elevations in pancreatic exocrine enzyme level, new-onset type 1 diabetes mellitus, and allopurinol hypersensitivity syndrome have been reported in a 58-year-old Cambodian female.[Ref]

Gastrointestinal side effects including diarrhea, nausea, and vomiting have been reported in less than 1% of patients. At least one case of steatorrhea has also been reported, in addition to a case of elevations in pancreatic exocrine enzyme level.[Ref]


A 43-year-old female with chronic kidney disease developed fever, generalized morbilliform rash, leukocytosis with marked eosinophilia, and hepatic dysfunction 3 weeks after starting allopurinol therapy (300 mg/day for 3 days followed by 200 mg/day) for hyperuricemia and arthritis. Pure red cell aplasia was suspected due to progressive worsening of anemia with reticulocytopenia. Treatment with recombinant human erythropoietin was initiated in addition to prednisolone 15 mg daily. Eleven days later (approximately 7 weeks after allopurinol was discontinued), both the hemoglobin level and reticulocyte count began to rise.[Ref]

Hematologic side effects including bone marrow suppression, resulting in severe anemia, thrombocytopenia, and leukopenia have been reported in 0.2% of patients. In addition, aplastic anemia, sometimes fatal, and hemolytic anemia have been reported. At least one case of pure red cell aplasia has also been reported.[Ref]


Studies of patients with allopurinol-induced crystalluria and nephrolithiasis have revealed both urate and allopurinol/oxypurinol (allopurinol metabolite) calculi. Biopsies in cases of suspected allopurinol-associated acute renal failure have revealed vasculitis, interstitial nephritis, and rare cases of granulomatous nephritis.[Ref]

Renal side effects have included crystalluria and stone formation as well as elevations in blood urea nitrogen. Acute interstitial nephritis due to hypersensitivity and granulomatous nephritis have also been reported.[Ref]

Nervous system

Allopurinol-induced aseptic meningitis has been reported in two isolated cases where 60-year-old Caucasian men developed high fevers soon after taking an initial dose of 300 mg allopurinol, and when rechallenged, with quick improvement after allopurinol was stopped.

There is a case report of a patient with no history of psychiatric disease whose allopurinol-associated catatonia, rash, and fever responded to steroids.[Ref]

Nervous system side effects have been reported extremely rarely and included case reports of peripheral neuropathy, catatonia, and cerebral vasculitis associated with allopurinol hypersensitivity. At least two cases of allopurinol-induced aseptic meningitis have also been reported.[Ref]


Anterior lens thinning is associated with cataract formation, and is more common among patients on allopurinol therapy.[Ref]

Ocular side effects have included cataract formation. Macular retinitis, iritis, conjunctivitis, and amblyopia have also been reported, although causality is unknown.[Ref]


Immunologic side effects have included at least one case of ANCA-positive vasculitis.[Ref]

Antineutrophil cytoplasmic antibodies (ANCA) against human neutrophil elastase as well as against myeloperoxidase were documented in a 47-year-old man who developed vasculitis during allopurinol therapy for gout. Clinical improvement and decline in antibodies were noted upon discontinuation of allopurinol.[Ref]


A first of a kind case report, new-onset type 1 diabetes mellitus, elevations in pancreatic exocrine enzyme level, and allopurinol hypersensitivity syndrome have been reported in a 58-year-old Cambodian female.

Metabolic side effects including at least one case of new-onset type 1 diabetes mellitus have been reported.


Musculoskeletal side effects have included acute attacks of gout.


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Not all side effects for allopurinol may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

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