Azathioprine is a drug that inhibits the activities of the body immunity defense system. It is available in various forms such as tablets and liquid solution for direct injection into the body. It is used to treat inflamed joint linings, joint pain and as a drug agent which prevents the immune system to attack new body organs during transplant. The long term use of Azathioprine may build the chances for the development of various types of cancers like leukemia and lymphoma. As this medication interacts with the working of body defense system it may lead to an increase in infection attack. Its dosage depends upon the health conditions and weight of the patients.