Azathioprine
(Imuran, Azasan) and 6-mercaptopurine (6-MP, Purinethol) are the standard oral immunosuppressant drugs. However, it can take 3 - 6 months for these drugs to have an effect. They can be combined with corticosteroids to speed up the response.
This drug alters the immune response by inhibition of natural killer cell activity and suppression of T-cell function, and thus decreasing inflammation.
Azathioprine and 6-mercaptopurine are effective therapy for inducing remission in active Crohn's disease. The odds ratio of response increases after > 17 weeks of therapy, suggesting that there is a minimum length of time for a trial of azathioprine or 6-mercaptopurine therapy (Prefontaine E et al, 2009)Prefontaine E, Macdonald JK, Sutherland LR. Azathioprine or 6-mercaptopurine for induction of remission in Crohn's disease. Cochrane Database Syst Rev. 2009, 7:(4). Review..
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Side Effects
The most common and serious side effect of azathioprine involves the cells of the blood and gastrointestinal system. Azathioprine can cause serious lowering of the white blood cell count, resulting in an increased risk of infections. This side effect can be life-threatening. This effect can be reversed when the dose of azathioprine is reduced or temporarily discontinued. Azathioprine can cause liver toxicity. All patients taking azathioprine require regular testing of blood for blood cell counts and liver tests to monitor for side effects of azathioprine. Other side effects encountered less frequently include fatigue, hair loss, joint pains, and diarrhea. Azathioprine can also cause nausea, vomiting, and loss of appetite, which may resolve when the dose is reduced.