Thiopurine Induced Pancreatitis in IBD Patients

Azathioprine (AZA) and its metabolite 6-mercaptopurine (6-MP) were developed over 50 years ago by Gertrude Elion and George Hitchings and were initially used clinically in the management of childhood leukemia and organ transplantation. The first case report of 6-MP use in inflammatory bowel disease (IBD) was from 1962 , and since then the use of thiopurines has been well established in the management of moderate to severe IBD. Thiopurines offer an inexpensive and effective treatment option for maintenance of remission of IBD in comparison to biological agents which may be 30 times more expensive . Although 50-60% of IBD patients respond to thiopurines, a significant proportion of patients will not tolerate them due to various adverse effects . The adverse effects of thiopurines may be dose related, patient related or idiosyncratic. The immunosuppressive effects of thiopurines also increase the rates of opportunistic infections. Thiopurines are also associated with a higher rate of malignancies, particularly a malignant Burkitt-like lymphoma, related to Epstein-Barr virus infection . Other adverse effects of thiopurine relate to allergic phenomenon. An idiosyncratic adverse effect of thiopurine use is acute pancreatitis (AP). Acute inflammation of the pancreas defined by INSPPIRE criteria: requiring 2 of: 1. Abdominal pain compatible with AP 2. Serum amylase and/or lipase ≥ 3 times upper limits of normal 3. Imaging findings of AP Drug induced AP is the assumed diagnosis when no other cause of AP can be found, the patient is taking a drug known to be associated with AP, and symptoms resolve after drug discontinuation. If pancreatitis re-occurs on re-exposure, the drug is definitely considered the cause. While drugs are considered a rare cause of AP and most cases are mild and self limited , there is an 8 fold higher risk of AP in IBD patients treated with AZA . Thiopurine induced AP is usually detected within 4 weeks of starting treatment. However in the c