Background: Azathioprine (AZA) and 6-mercaptopurine (6-MP), purine analogues, are the immunosuppressant drugs most frequently used for inducing and maintaining remission in inflammatory bowel disease (IBD). The occurrence of adverse effects is a major drawback in the use of these drugs, and short- and long-term toxicity represent a major limitation to their use.
Aim: The present study investigated the prevalence, type and time of onset of AZA-related adverse events, in a cohort of IBD patients in a single referral Centre.
Patients and methods: The records of consecutive IBD outpatients, referred to our Institution between 1987-2009, were retrospectively evaluated.
Results: We reviewed 2014 patients, in whom AZA was prescribed in 302 of them, 139 (46%) with ulcerative colitis (UC) and 163 (54%) with Crohn's disease (CD). Side-effects were complained by 98 (32.4%) out of 302 patients, 50 UC and 48 CD, (36% UC vs 29.4% CD, p = 0.26). In 20 (20.4%) patients, 11 UC and 9 CD, side-effects recovered after dosage reduction whilst in 78 (79.6%), 39 UC and 39 CD, the treatment was discontinued (dose-dependent side-effects in 42 patients and dose-independent in 36). Overall, side-effects were observed after a mean period of 14.5 ± 7.8 months (range 0.5-123) of AZA treatment. The majority (76%) of the dose-dependent adverse events were reported between 12-18 months after the beginning of treatment.
Conclusions: The prevalence of side effects leading to withdrawal of AZA treatment, in our series of Italian patients, was higher respect to data reported in the literature (25.8%).