In the treatment of immune mediated diseases, it is the stimulated lymphocytes that are inappropriately attacking the body that become the prime target of azathioprine. Because Azathioprine can disrupt rapid cell division, its use also has application in treating cancers. Because Azathioprine is a DNA poison it has the potential to cause mutation. Cells of the bone marrow are rapidly dividing and thus at risk for suppression from azathioprine. If bone marrow suppression has not occurred in the first couple of months of therapy, it is unlikely that it will occur later on.
Some patients develop a liver toxicity with azathioprine.
This should resolve with discontinuation of the medication but it is important to watch for any signs of nausea, diarrhea, or appetite loss. If these occur, especially in the first few weeks of starting azathioprine, discontinue the medication and notify your veterinarian of these effects. Similarly, azathioprine can promote pancreatitis . If this occurs, discontinue azathioprine and notify your veterinarian. Because it can take a good month or two before the benefits of azathioprine are seen, it is a good idea to begin azathioprine in conjunction with an aggressive prednisone course.