An improved understanding of thiopurine metabolism has enabled individualized dosing of these agents in patients with IBD. Ansari et al. describe the use of allopurinol to deliberately manipulate thiopurine metabolism in patients who previously could not tolerate therapeutic doses of azathioprine or 6-mercaptopurine. This therapeutic maneuver potentially enables this therapy to be given to a considerable subgroup of patients otherwise unable to tolerate thiopurine therapies.
