High Quality Content by WIKIPEDIA articles! A xanthine oxidase inhibitor is any substance that inhibits the activity of xanthine oxidase, an enzyme involved in purine metabolism. In humans, inhibition of xanthine oxidase reduces the production of uric acid, and several medications that inhibit xanthine oxidase are indicated for treatment of hyperuricemia and related medical conditions including gout. Xanthine oxidase inhibitors are being investigated for management of reperfusion injury. Xanthine oxidase inhibitors are of two kinds: purine analogues and others. Purine analogues include allopurinol, oxypurinol, and tisopurine. Others include febuxostat and inositols (phytic acid and myo-inositol).