Rituximab is a medication used to treat certain autoimmune diseases and types of cancer.It is used for non-Hodgkin's lymphoma, chronic lymphocytic leukemia, rheumatoid arthritis, granulomatosis with polyangiitis, idiopathic thrombocytopenic purpura, pemphigus vulgaris and myasthenia gravis.It is given by slow injection into a vein.