Thrombocytopenia and leukopenia are dose dependent and may be reversed by reducing the dose or temporarily discontinuing use of azathioprine. Other reported hematologic adverse effects include eosinophilia, leukocytosis, neutropenia, anemia, aplastic anemia, and fatal myelogenous leukemia.
Results of one small study suggest that analysis of thiopurine methyltransferase genotype may allow identification of patients who are at risk for azathioprine hematologic toxic effects. The authors consider testing to be cost-effective compared with the cost of blood monitoring and supportive care for the 2%-12% of patients with this toxic effect (Black et al. 1998).
Data from the National Cooperative Crohn's Disease Study identified six patients (5.3%) with pancreatitis who were treated with azathioprine alone (Sturdevant et al. 1979). Associated symptoms include abdominal pain, elevated amylase and lipase levels, and vomiting.
Azathioprine can be hepatotoxic, and associated symptoms may include anorexia, nausea, fatigue, weight loss, jaundice, pruritis, dark urine, and elevated LFTs. Ideally, LFTs should be monitored every 2 weeks for the first 4 weeks and every 1-3 months thereafter (Gaffney and Scott 1998).
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