Allopurinol gastrointestinal effects

The daily dose of allopurinol is 300-600 mg. In combination with benzbromarone, the daily allopurinol dose is reduced to 100 mg. In general, allopurinol is well tolerated. The incidence of side effects is 2-3%. Exanthems, pruritus, gastrointestinal problems, and dty mouth have been observed. In rare cases, hair loss, fever, leukopenia, toxic epidermolysis (Lyell syndrome), and hqDatic dysfunction have been reported. Allopurinol inhibits the metabolic inactivation of the cytostatic dtugs azathioprine and 6-mercaptopurine. Accordingly, the administered doses of azathioprine and 6-mercaptopurine must be reduced if allopurinol is given simultaneously. 

The daily dose of benzbromarone is 50-200 mg. In combination with allopurinol, the benzbromarone dose is reduced to 20 mg. Benzbromarone is well tolerated. Rare side effects are headaches, gastrointestinal problems, and exanthems. 

Major limitations of the use of allopurinol are allergy, hypersensitivity syndromes, hepatotoxicity, bone marrow suppression, nonspecific central nervous system and gastrointestinal side effects. Skin rash occurs in 2% and Steven-Johnson syndrome, although rare, may occur. The latter can cause life-threatening major organ system failure. 

The major side effects associated with uricosuric therapy are gastrointestinal irritation, rash and hypersensitivity, precipitation of acute gouty arthritis, and stone formation. These drugs are contraindicated in patients who are allergic to them and in patients with impaired renal function (a creatinine clearance <50 mL/min), a history of renal calculi, and in patients who are overproducers of uric acid for such patients, allopurinol should be used. 

Allopurinol is the antihyperuricemic drug of choice in patients with a history of urinary stones or impaired renal function, in patients who have lymphoproliferative or myeloproliferative disorders and need pretreatment with a xanthine oxidase inhibitor before initiation of cytotoxic therapy to protect against acute uric acid nephropathy, and in patients with gout who are overproducers of uric acid. The major side effects of allopurinol are skin rash, leukopenia, occasional gastrointestinal toxicity, and increased frequency of acute gouty attacks with the initiation of therapy. An allopurinol hypersensitivity syndrome characterized by fever, eosinophilia, dermatitis, vasculitis, and renal and hepatic dysfunction is a rare side effect, but is associated with a 20% mortality rate. ... 

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