Immunomodulators: Azathioprine/6-Mercaptopurine and Methotrexate

Treatment aims in the inflammatory bowel diseases (IBDs) are evolving beyond the induction and maintenance of corticosteroid-free remission. More recently, it has become recognized that by treating with immunomodulatory and biologic therapies earlier in the disease course, and achieving mucosal healing, the natural history of these diseases may be modified in a positive way. Despite the clear benefits of early and appropriate introduction of these therapies, the potential for risks, some of them serious, must be understood by the clinician and discussed with patients. This chapter will review the relevant adverse events associated with the use of the immunomodulatory agents azathioprine (AZA), 6-mercaptopurine (6-MP), and methotrexate (MTX).