Thiopurine Methyltransferase Enzyme Activity Determination before Treatment of Inflammatory Bowel Disease with Azathioprine: Effect on Cost and Adverse Events

BACKGROUND: Azathioprine (AZA), used to treat inflammatory bowel disease (IBD), is metabolized by thiopurine methyltransferase (TPMT). The accumulation of individual metabolites varies because humans display genetic polymorphism for TPMT expression. Deficiencies in TPMT result in accumulation of toxic metabolites, followed by neutropenia and hepatic inflammation. Concern over acute toxicity frequently leads to under dosing and frequent monitoring tests and visits