Azathioprine was first made in 1957. It is on the World Health Organization's List of Essential Medicines. In 2017, it was the 335th-most commonly prescribed medication in the United States, with more than 800,000 prescriptions. Azathioprine (AZA), sold under the brand name Imuran, among others, is an immunosuppressive medication. azathioprine use in rheumatoid arthritis, granulomatosis with polyangiitis, Crohn's disease, ulcerative colitis, and systemic lupus erythematosus, and in kidney transplants to prevent rejection. It is taken by mouth or injected into a vein. It's been used in some patients with multiple sclerosis (MS), usually if they have problems with standard FDA-approved medications for their MS.