Allopurinol is a xanthine oxidase (XO) inhibitor which inhibits the activity of xanthine oxidase, an enzyme involved in purine metabolism. XO catalyzes the oxidative hydroxylation of hypoxanthine [
H0311] to xanthine [
X0004] and further catalyze the oxidation of xanthine to uric acid [
U0018]. Hence, XO inhibitors can lower serum levels of uric acid. In additon, febuxostat [
F0847] is a non-purine inhibitor of XO. Allopurinol, first synthesized as a potential antitumor agent, is nowadays a clinical useful XO inhibitor used in the treatment of gout and the prevention of tumor lysis syndrome. (The product is for research purpose only.)