Imuran (azathioprine) is an immunosuppressive medication classified as a purine antimetabolite. It works by interfering with the production of DNA and RNA in rapidly dividing cells, particularly immune cells. This mechanism helps to suppress the immune system and prevent it from attacking healthy tissues. Imuran is commonly used in the treatment of autoimmune conditions such as rheumatoid arthritis, lupus, inflammatory bowel disease, and to prevent rejection in organ transplant recipients.