Azathioprine

Current indication

For use in patients who are unable to tolerate mycophenolate mofetil.

Dose
  • Initial –¬†1-2 mg/kg once daily.
  • Maintenance –¬†1 mg/kg once daily.
  • Monitoring¬† – No monitoring of drug levels is required.
Preparation

Azathioprine is available as 25 mg and 50 mg tablets. There are both generic and brand (Imuran) forms on the market.

Administration

Virtually exclusively oral although an IV preparation is available.

Contra-indications
  • Pregnancy.
  • Bone marrow dysfunction, i.e. patients who are known to be leucopaenic or thrombocytopaenic.
  • Reduce dose if hepatic dysfunction is present.
Drug interactions

Allopurinol and Febuxostat must not be co-prescribed as an inhibition of xanthine oxidase results in potentially fatal accumulation of azathioprine and its metabolites. An alternative uricosuric- benzbromarone is available on a named patient basis. Contact transplant unit pharmacist for further details.

Side Effects
  • Bone marrow suppression – usually reversible following cessation.
  • Cholestatis and disturbed liver function – again usually reversible.
  • Pancreatitis

Dose may require to be altered depending on WCC, ie. reduce if WCC<4.0, stop if WCC <3.0 and re-introduce at a lower doses when WCC>3.0.