What is allopurinol "failure" and what should we do about it?

Allopurinol is the most widely used urate-lowering medication world-wide. However, allopurinol "failure" is frequently observed in clinical practice. In this review, we provide a framework for assessing allopurinol "failure", which includes failure of allopurinol to control serum urate concentrations, failure of allopurinol to control clinical symptoms, and failure of allopurinol due to an adverse drug reaction. Understanding the causes of allopurinol "failure" underpins the approach required to turn "failure" into "success" in gout management.