Displaying 6 results of Azathioprine Impurities Azathioprine is a medication used to treat autoimmune diseases and prevent organ rejection after transplant surgery. However, the drug may contain impurities that can cause adverse effects on the body. These impurities may include degradation products, related substances, and residual solvents. Hence, quality control measures are necessary to ensure the safety and efficacy of Azathioprine.