Objective: Azathioprine and 6-mercaptopurine are useful therapies in inflammatory bowel diseases. Despite their efficacy, their use is limited owing to treatment intolerance or toxicity in 10-15% of patients. It has been suggested that both drugs could be interchangeable.
Material and methods: All patients treated with 6-mercaptopurine because of previous digestive intolerance of azathioprine in four Spanish hospitals were reviewed. Tolerance of 6-mercaptopurine therapy was assessed.
Results: Fifteen patients (11 Crohn's disease, 4 ulcerative colitis) were included. Immunosuppressant therapy was prescribed for steroid-dependent disease in 13 cases, and for perianal disease in 2. Main symptoms of digestive intolerance were epigastric pain, nausea and vomiting, which developed within the first weeks of treatment. Acute pancreatitis was ruled out in all the cases. Five patients commenced 6-mercaptopurine immediately after azathioprine discontinuation and 7 patients within the first month. Eleven patients (73.3%) tolerated 6-mercaptopurine and reached the therapeutic goals; only two patients had to discontinue 6-mercaptopurine because of adverse effects.
Conclusions: Treatment with 6-mercaptopurine is a safe alternative in patients with inflammatory bowel diseases and previous digestive intolerance of azathioprine.