Tolerance and Efficacy of Azathioprine in Pediatric Crohn's Disease

Background: Thiopurines are considered first-line immunomodulators for the prevention of relapse in moderate to severe pediatric Crohn's disease (CD). Early introduction of thiopurines was shown in a pediatric trial to maintain steroid-free remission in 90% of patients for 18 months. In the present study we analyzed the tolerance and efficacy of azathioprine (AZA) to maintain remission in a homogenous single-center observational cohort of children with CD. Methods: In all, 105 pediatric CD patients (male/female 68/37) were retrospectively evaluated for the efficacy of AZA (doses 1.4-4 mg/kg) to maintain remission at 6, 12, 18, and 24 months of follow-up. Overall, 93 children were included with active disease (pediatric Crohn's disease activity index [PCDAI] >30), steroid/enteral-nutrition dependency, or postileocecal resection. Remission was defined as PCDAI <= 10 without steroids. Patients requiring antitumor necrosis factor (TNF) medication, other immunomodulators, or surgery were considered to experience a relapse. Results: Based on PCDAI, steroid-free remission was achieved in 56/93 (60.2%), 37/93 (39.8%), 31/93 (33.3%), and 29/93 (31.2%) at visits month (M)6, M12, M18, and M24, respectively. Within the first 4 weeks, AZA was stopped in 10/93 patients due to adverse reactions (pancreatitis, nausea, vomiting, skin reactions, general weakness), or not introduced due to low thiopurine methyl transferase (TPMT) activity (n = 3). No neutropenia occurred in patients with normal TPMT activity. Three infectious episodes were documented requiring temporary AZA suspension. Conclusions: AZA is efficacious in maintaining remission in pediatric CD patients, but to a lesser extent than previously suggested. The majority of patients who are in steroid-free remission at 12 months remained in prolonged remission. Overall tolerance of AZA was excellent.