Cytotoxic agents are dangerous medications, which may be used to treat major and possibly even life-threatening diseases. Cytotoxic agents were initially introduced in medicine for their ability to interrupt nucleic acid and protein synthesis in malignant cells. Subsequently, and on the basis of their immune-suppressing capacities, they were used for the prevention of rejection of allogenic transplanted organs (azathioprine, cyclosporine, and mycophenolate mofetil). The realization that these agents exhibit immunomodulatory capacities led to their use in autoimmune diseases including systemic lupus erythematosus (SLE).