Figure 3From: Gout. Novel therapies for treatment of gout and hyperuricemiaComparison of allopurinol, oxypurinol, and febuxostat structures. Allopurinol and its long-lived major active metabolite oxypurinol (both pictured) inhibit xanthine oxidase, as does febuxostat (pictured), which, in contrast to the other two agents, does not have a purine-like backbone.Back to article page