Azathioprine

Key points

• Azathioprine is metabolised to the active compound mercaptopurine, a purine analogue that inhibits purine synthesis
• A thiopurine methyltransferase (TPMT) test may be needed beforehand to identify individuals at risk of azathioprine toxicity
• Adverse effects: bone marrow depression, nausea/vomiting, pancreatitis
• Significant interaction with allopurinol — lower doses of azathioprine should be used if co-prescribed