Oxipurinol (CAS 2465-59-0) is a small molecule inhibitor of xanthine oxidoreductase (XO) an enzyme integral to purine metabolism As the principal active metabolite of allopurinol oxipurinol functions as a noncompetitive XO inhibitor contributing significantly to the pharmacological effects observed with allopurinol therapy In vitro studies indicate that both allopurinol and oxipurinol demonstrate XO inhibition and exhibit free radical scavenging properties with evidence of cardioprotective effects independent of XO activity In vivo oxipurinol administration has been shown to reduce vascular free radical production in hypercholesterolemic animal models Its pharmacokinetic profile is characterized by predominant renal clearance Oxipurinol is widely utilized in research exploring oxidative stress cardiovascular physiology and disorders of purine metabolism