Letter: azathioprine‐induced pancreatitis and subsequent tolerance of mercaptopurine

Abstract

We read with interest the paper by Kennedy et al. describing patients with inflammatory bowel disease (IBD) who had been intolerant of azathioprine and had subsequently been trialled with mercaptopurine.1 It was an interesting article, but it did not highlight some recent data that indicate that the development of azathioprine-induced pancreatitis is not necessarily a strict contraindication to subsequent use of mercaptopurine. Thiopurine-induced pancreatitis occurs in up to 5% of patients and is an idiosyncratic drug reaction. In our study published earlier this year, we described 64 patients with IBD over 10 years of whom 23 were intolerant to azathioprine, seven of whom developed acute pancreatitis. In all seven patients, the pancreatitis was mild and resolved within a few days of withdrawal of azathioprine. Three of these seven patients with azathioprine-related pancreatitis then went on to tolerate mercaptopurine.2 Ledder et al. also recently described a case series of four paediatric patients with IBD who developed azathioprine-induced pancreatitis. The subsequent trial of mercaptopurine was tolerated in all four patients, leading to the conclusion that the results called into question that azathioprine-induced pancreatitis is an absolute contraindication to the use of mercaptopurine and is most relevant in those with an aggressive phenotype where long-term immunosuppression is required.3 Azathioprine-induced pancreatitis should not be considered a strict contraindication to the subsequent use of mercaptopurine in patients with IBD. Introduction of mercaptopurine following azathioprine-induced pancreatitis in a controlled setting should be considered. Declaration of personal and funding interests: None.