Contraindications of Azathioprine in ITP

Absolute Contraindications

Very low or absent TPMT activity is an absolute contraindication due to the high risk of life-threatening pancytopenia and profound myelosuppression 1, 2, 3, 4
Known hypersensitivity to azathioprine or 6-mercaptopurine is an absolute contraindication 1, 2, 3, 4
Concurrent allopurinol treatment is contraindicated—if unavoidable, azathioprine dose must be reduced to approximately 1/3 to 1/4 the usual dose due to severe myelosuppression risk 1, 3, 4

Azathioprine is contraindicated in pregnancy except where benefit may outweigh risk (such as in allograft recipients) 1, 2, 3, 4
Women on azathioprine should not breastfeed their babies—6-mercaptopurine has been identified in colostrum and breast milk 1, 2, 3, 4
Azathioprine treatment should not usually be initiated or continued in patients with known malignancy, as immunosuppression may increase the risk of disease progression 1, 2, 3, 4
Severely impaired hepatic or bone marrow function is a contraindication 1, 2, 3, 4
Severe infections are a contraindication to azathioprine initiation 2
Active pancreatitis is a contraindication—acute pancreatitis is a rare but well-recognized side effect of azathioprine 5

While ITP itself causes thrombocytopenia, patients with additional severe baseline cytopenias (severe leukopenia or anemia) require careful consideration 6
Moderate leucopenia common in cirrhosis probably does not increase the risk of azathioprine-related marrow depression per se, but complicates haematological monitoring 6

Do not start azathioprine without checking TPMT status first—this is a critical safety measure that cannot be skipped 1, 2, 3, 4
Elderly patients require doses at the lower end of the recommended range with additional haematological monitoring due to higher incidence of side effects 5