Azathioprine in Immune Thrombocytopenic Purpura (ITP) Treatment

Positioning in ITP Treatment Algorithm

Azathioprine is classified as a second-line therapy option for ITP, alongside other agents such as rituximab, splenectomy, and thrombopoietin receptor agonists, and should be considered after failure of first-line therapies or when patients have contraindications to these treatments 1, 2, 3, 4
The main goal when using azathioprine is to attain a sustained increase in platelet count that provides hemostasis for the individual patient 1

Standard dosing is 1-2 mg/kg daily (maximum: 150 mg/day) 5, 6
Patients should be monitored for thiopurine methyltransferase deficiency if cytopenias develop, as approximately 0.25% of the population lacks this enzyme 7
Response to azathioprine is typically slow, requiring continued administration for 3-6 months before determining efficacy 6

Complete response rates of approximately 45% have been reported in patients treated with azathioprine (150 mg/day) for a median of 18 months 1, 2
Up to two-thirds of patients may show some response to therapy, although the exact percentage may vary 5

Although continued therapy is generally required to maintain response, often a reduced dose suffices 1, 2

Azathioprine has a relatively favorable safety profile with generally mild side effects 1, 2
Common adverse effects include weakness and sweating, and transaminase elevations 5
Unlike cyclophosphamide, leukemia has only rarely been associated with azathioprine in other disorders and has not been described in ITP patients 1, 2
Azathioprine is one of the few ITP medications considered relatively safe in pregnancy, with no increased rate of fetal malformation, and is safe during lactation 7

Azathioprine may be particularly valuable in settings where access to newer therapies like TPO receptor agonists is limited due to cost constraints 8
Azathioprine represents a cost-effective second-line option in resource-limited settings, particularly for patients who cannot tolerate other agents 7, 8