Azathioprine

Question 1

What are the contraindications for Azathioprine?

Answer 1

Absent or very low TPMT activity
Hypersensitivity to mercaptopurine

Question 2

When should dose be reduced?

Answer 2

In the elderly, if there is reduced TPMT activity, hepatic failure, hepatic or haematological toxicity, renal impairment- reduce starting dose.

Question 3

What are the potentially severe interactions?

Answer 3

Allopurinol: haematological toxicity
Feboxostat: incraesed exposure
BCG vaccine/ any live vaccine : risk of potentially life threatening infection
ACE Inhibitors: increased risk of anaemia and/or leucopenia

Question 4

What side effects are associated with toxicity and may require drug withdrawal?

Answer 4

Hypersensitivity reactions - dizziness, dairrhoea, vomiting rigors etc
Neutropenia and thrombocytopenia - dose dependent
Nausea - common at the start of treatment and will resolve in few weeks without alteration in dose. Any longer may need dose reduction.

Question 5

Should azathioprine be stopped in pregnancy?

Answer 5

Transplant patients should not stop but there have been reports that azathioprine is teratogenic

Question 6

Can azathioprine be taken when breastfeeding?

Answer 6

present in milk in small concentrations but no evidence of harm in small studies

Question 7

What pre treatment screening needs to be done?

Answer 7

TPMT

Question 8

What are the monitoring requirements?

Answer 8

FBC weekly for 4 weeks
Then 3 monthly thereafter

Monitor for toxicity throughout treatment

Question 9

When should IV route be used and why?

Answer 9

Only when oral route is not feasible
IV injection is alkaline and very irritant

Question 10

What are the cautionary advisory levels

Answer 10

Take with or just after food.