Azathioprine

Azathioprine is metabolised to the active compound mercaptopurine, a purine analogue that inhibits purine synthesis. A thiopurine methyltransferase (TPMT) test may be needed to look for individuals prone to azathioprine toxicity.

Adverse effects include

• bone marrow depression
  • consider a full blood count if infection/bleeding occurs
• nausea/vomiting
• pancreatitis
• increased risk of non-melanoma skin cancer

A significant interaction may occur with allopurinol and hence lower doses of azathioprine should be used.

Azathioprine is generally considered safe to use in pregnancy.