 However, when the outcomes were evaluated separately, febuxostat showed an increased risk of heart-related deaths and death from all causes.Febuxostat is contraindicated with concomitant use of theophylline and chemotherapeutic agents, namely azathioprine and 6-mercaptopurine, because it could increase blood plasma concentrations of these drugs and thereby their toxicity.Febuxostat is a non-purine-selective inhibitor of xanthine oxidase.