Allopurinol is a well tolerated, inexpensive, and commonly used uric acid lowering agent. Allopurinol can be started at doses as low as 100 mg daily (100 mg qod if creatinine clearance < 10 cc/min) and titrated by 100 mg every 10-14 days to achieve a serum uric acid level of 4-5 mg/dl. Liver tests, blood counts, and renal function and should be monitored while on therapy. Toxicites include rash, hepatoxicity, bone marrow suppression and severe hypersensitivity reactions. Medication interactions can occur with allopurinol, warfarin, and theophylline and levels should be monitored. Allopurinol should be avoided in patients on azathiprine, 6-mercaptopurine and cyclophosphamide because of risk for bone marrow toxicity.
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Hyperuricemia is a classic feature of gout, but nearly half of the time gout occurs without hyperuricemia and most people with raised uric acid levels never develop gout.   Thus, the diagnostic utility of measuring uric acid levels is limited.  Hyperuricemia is defined as a plasma urate level greater than 420 μmol/l ( mg/dl) in males and 360 μmol/l ( mg/dl) in females.  Other blood tests commonly performed are white blood cell count , electrolytes , kidney function and erythrocyte sedimentation rate (ESR). However, both the white blood cells and ESR may be elevated due to gout in the absence of infection.   A white blood cell count as high as ×10 9 /l (40,000/mm 3 ) has been documented.