Safety of azathioprine and 6-mercaptopurine in pediatric patients with inflammatory bowel disease

Background & Aims: Azathioprine (AZA) and 6-mercaptopurine (6-MP) are used in pediatric patients with ulcerative colitis and Crohn's disease to reduce disease activity, maintain remission, prevent relapse, and lower corticosteroid dosage, but their long-term side effects remain to be studied. The aim of this study was to analyze the safety of AZA and 6-MP and steroid reduction in this age group. Methods: The investigators' database identified 118 patients who received either drug; 23 were excluded (single visit, noncompliance, or therapy < 1 week), leaving 95 patients, with a mean (+/-SD) age of 14.2 +/- 4.4 years. Medical files were reviewed for adverse side effects: fever, pancreatitis, infections, gastrointestinal intolerance, aminotransferase level increase, leukopenia, and thrombocytopenia. Prednisone doses before and after immunomodulatory therapy were compared. Results: AZA or 6-MP was tolerated in 51 of 95 patients (54%) without adverse reaction; 27 of 95 (28%) experienced side effects that responded to dose reduction 1:23 patients) or spontaneously (4 patients), most commonly increased aminotransferase level (13.7%). Cessation of therapy was needed in 17 of 95 patients (18%), including recurrent fever (4), pancreatitis (4), gastrointestinal intolerance (4), and recurrent infections (3). Mean prednisone dose decreased from 24.3 to 8.6 mg/day. Conclusions: AZA and 6-MP were well tolerated in 82% of patients; of these, prednisone reduction occurred in 87%. However, 18% required discontinuation because of hypersensitivity or infectious side effects.