RITUXIMAB (ri TUX i mab) is a monoclonal antibody. This medicine changes the way the body's immune system works. It is used commonly to treat non-Hodgkin's lymphoma and other conditions. In cancer cells, this drug targets a specific protein within cancer cells and stops the cancer cells from growing. It is also used to treat rhuematoid arthritis (RA). In RA, this medicine slow the inflammatory process and help reduce joint pain and swelling. This medicine is often used with other cancer or arthritis medications.