Azathioprine or 6-mercaptopurine for maintenance of remission in Crohn's disease

Azathioprine (1.0 to 2.5 mg/kg/day) used among patients with non-active Crohn's disease is effective for reducing the risk of disease recurrence over a 6 month to 2 year period. Higher doses of azathioprine (2.5 mg/kg/day) are more effective than lower doses (1.0 or 2.0 mg/kg/day) for preventing disease recurrence. There is also evidence that azathioprine may reduce the need for steroid treatment which could help reduce steroid related side effects. 6-Mercaptopurine may be effective for reducing the risk of disease recurrence over a 2 year period. Azathioprine appears to be more effective than 6-mercaptopurine but this may be due to the relatively low dose of 6-mercaptopurine (50 mg/day) used in the one study assessing this drug. Future studies should assess the effect of higher doses of 6-mercaptopurine. The long-term effectiveness of azathioprine and 6-mercaptopurine is unclear due to the short duration of the studies (6 months to 2 years). Azathioprine and 6-mercaptopurine appear to be slow acting drugs. They are associated with some uncommon but serious side effects. These include suppression of the body's ability to produce white blood cells (which fight infection) and platelets (which allow blood clotting to occur), inflammation of the pancreas and an increased risk of lymphoma. Patients who may benefit from this therapy include those whose Crohn's disease is chronically active or flares frequently. Azathioprine or 6-mercaptopurine may also benefit patients who are dependent on steroids but have experienced steroid side effects, or for whom steroids no longer work. The choice to use azathioprine or 6-mercaptopurine should be made after careful consideration of the risks and benefits of using these drugs.