This a cytotoxic immunosuppressant with similar actions to those of mercaptopurine, to which it is converted in the body.

Indications: transplant recipient and also in a number of autoimmune conditions, usually when corticosteroid therapy alone has provided inadequate control.

Cautions: reduce dose in renal failure and when allopurinol is given concurrently; blood picture monitoring is necessary; hepatic and renal impairment; pregnancy.

Contra-indications: hypersensitivity to azathioprine or mercaptopurine.

Side effect: bone marrow depression (dose-related); hepatic toxicity, hyper-sensitivity reactions; hair loss; increased susceptibility to infections and colitis.

Dose: by mouth, autoimmune conditions, 1-3mg/kg daily. Suppression of transplant rejection, initially up to 5mg/kg then 1-4mg/kg daily according to response.