High-dose azathioprine in children with inflammatory bowel disease

Background: Azathioprine is widely used as maintenance therapy in children with moderate to severe inflammatory bowel disease (IBD). There is no data on safety at higher doses and its impact on growth and surgical morbidity in children. Methods: This retrospective cohort study included all children treated with azathioprine and diagnosed with IBD between 1996-2001. Outcome measures included indications for azathioprine use, adverse-effects and reasons for treatment discontinuation. Height and weight at diagnosis, treatment onset and current follow-up was recorded, and Z scores for height standardised for time. Results: 107 children received azathioprine at 3 mg/kg. 61% had Crohn's disease and 83% started azathioprine within 2 years of diagnosis. Only 2/107 children had to stop azathioprine because of persistent adverse effects and 16/107 required surgery. There was a trend toward better growth in a group of children with Crohn's disease following treatment with high dose azathioprine therapy (P = 0.08). Conclusions: Azathioprine is a safe and well-tolerated maintenance therapy at 3 mg/kg for children with IBD. The prevalence of surgery and growth failure in a cohort of children with moderate to severe IBD appears less than previously reported. In children with Crohn's disease, growth velocity may be maximised by an emphasis on nutritional therapy and the use of high dose azathioprine.