Tolerability profile of thiopurines in inflammatory bowel disease: a prospective experience

The occurrence of thiopurine-related adverse events (AEs) may complicate the management of patients with inflammatory bowel disease (IBD). We aimed to evaluate the tolerability of thiopurines in a current IBD setting.

All consecutive patients who started a treatment with azathioprine (AZA) from January 2010 to March 2016 were entered in a prospectively maintained database, and the AEs which led to the permanent discontinuation of the drug were reported.

Two hundred and fifty three patients were included. Median total follow-up was 32 months (range: 0.2-75 months). At the end of the study, AZA was discontinued in 160 patients (63.2%). The main reason leading to drug withdrawal was the occurrence of AEs (109/160 patients [68.1%]; cumulative incidence among the entire cohort: 43.1%). Overall, the most frequent AEs leading to treatment withdrawal were nausea (31/253 patients, 12.3%) and subjective symptoms, i.e., poorly defined side effects such as fatigue, headache and muscle pain (20/253 patients, 7.9%). Among the 109 AZA-intolerant patients, a switch to 6-mercaptopurine (6-MP) was performed in 44 cases (40.4%). At the end of follow-up, 6-MP was discontinued in 35/44 patients (79.5%), mostly due to AEs (29/35 patients, 82.8%). Azathioprine-induced hepatic and pancreatic toxicity was associated with male gender (p = .01 and p = .03, respectively), and occurrence of nausea with Crohn's disease (p = .04).

Our real-life prospective cohort showed the higher cumulative incidence of thiopurine withdrawal due to AEs reported to date. Switching from AZA to 6-MP was often ineffective.