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Last updated: Lesson of the Month - October 2017…
on 17 Oct 2017

Azathioprine



Indication
  • Prophylaxis of transplant rejection in liver, kidney or heart allograft recipients
  • It is also indicated for some auto-immune diseases, eg SLE
Preparations
  • Anti-proliferative immunosuppressant
  • Preparations: Tablets: 25mg, 50mg
  • Azathioprine does NOT need to be prescribed by brand
Contraindications
  • Hypersensitivity to azathioprine or 6-mercaptopurine (metabolite of azathioprine) or any of the excipients
  • Severe infections
  • Severe hepatic impairment
Cautions
  • Monitor FBC regularly; daily in immediate post-transplant period
  • Monitor LFTs regularly
  • Reduce dose in elderly
  • Live vaccines should be avoided
  • Should not be initiated in pregnancy, due to reports of premature and low birth weights. However it is continued in pregnancy if the patient is on it, since it is safer than other options

Note: drug coventionally given at 6pm in immediate transplant period, to allow for review of FBC
 

Side-effects
  • Dose-related bone marrow suppression
  • Infection and malignancies (esp lymphoma, skin and cervical cancer)
  • Nausea, diarrhoea, rash, hair loss
  • Hepatic dysfunction
  • Rarely pure red cell aplasia (PRCA)
Dose
  • 1-4 mg/kg/day (usually 1.5-3mg) as a once daily dose at 6pm to enable FBC to be checked
  •  IV dose equivalent to oral dose. Can be administered as bolus or as an infusion over 1 hour
Dose in renal impairment
  • As in normal renal function. 40-60% of a dose is lost during haemodialysis
Interactions
  • Bone marrow suppression occurs with azathioprine-allopurinol interaction. Reduce azathioprine dose by 50-75%, Medsafe, 1998). This is an important interaction
  • Other drugs that cause myelosuppression
How to Prescribe View Details
Patient comment
  • There is an increased risk of infection and certain cancers (including skin and cervical)
  • Avoid sunbathing, use high factor sun cream and women should attend for yearly cervical smears
  • Avoid live vaccines – ask your pharmacist
  • Swallow tablets whole do not crush tablets. Take with or after food

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