Bexxar is a monoclonal antibody used to treat relapsed or refractory CD20-positive non-Hodgkin's lymphoma. It binds to the CD20 antigen on B-cells and works through radiation, apoptosis induction, complement dependent cytotoxicity, and antibody-dependent cellular toxicity. Bexxar is given as a 450mg IV infusion followed by a calculated dose of I-131 tositumomab 7 to 14 days later. Common side effects include cytopenias, infusion reactions, and hypothyroidism. Precautions must be taken due to the radioactive iodine component.