azathioprine + allopurinol

Azathioprine + allopurinol is a combination of two drugs used primarily in immunosuppressive therapy, notably for inflammatory bowel disease (IBD) and organ transplantation. Azathioprine is an immunosuppressive agent that inhibits purine synthesis, thereby reducing DNA and RNA production which suppresses the immune system by decreasing white blood cell proliferation. It is metabolized to 6-mercaptopurine (6-MP), which is further metabolized by xanthine oxidase. Allopurinol is a xanthine oxidase inhibitor used to reduce uric acid levels in gout patients. When combined with azathioprine, allopurinol inhibits the metabolism of 6-mercaptopurine by blocking xanthine oxidase, leading to increased plasma levels of active metabolites of azathioprine. This interaction enhances the efficacy and tolerability of low-dose azathioprine therapy but carries a significant risk of severe bone marrow suppression (leukopenia, thrombocytopenia, pancytopenia) if doses are not properly adjusted. Therefore, when co-administered, the dose of azathioprine should be reduced to approximately 25% of its usual dose with close monitoring of blood counts.

Other names

azathioprine and allopurinol combination