Azathioprine is an immunosuppressant. It reduces the action of body's own defense
system (the immune system) and prevents rejection of the transplanted organ. It
also blocks the action of certain chemical messengers that are responsible for
inflammation, swelling, and redness associated with certain joint diseases.

Azathioprine is used to prevent your body from rejecting a transplanted kidney.
Azathioprine is also used to treat symptoms of rheumatoid arthritis.

Fever with chills
Sore throat
Abdominal pain
Loss of appetite
Muscle and joint pain
Nausea and Vomiting
Hair loss or thinning of the hair

This medicine may increase the risk of lymphoma and other malignancies. Doctors
should inform patients about these risks and advise the patient to prevent exposure
of the sunlight by wearing protective clothes.
This medicine may lower the blood cell count and may lead to a condition of severe
bone marrow suppression. 

The chances of occurring infections are more in the patients receiving this
medicine. 
This medicine is not recommended in the patients with the liver impairment.