Snapshot A 45-year-old woman with lung adenocarcinoma presents to the infusion center for her chemotherapy treatment. She had previously tolerated her treatment, but this infusion includes a newer chemotherapy agent. Fifteen minutes into her infusion, she feels very nauseous. The physician supervising prescribes her an anti-emetic medicine commonly used in the setting of chemotherapy. Introduction Drugs ondansetron Mechanism of action serotonin (5-HT3) receptor antagonist, which decreases vagal stimulation Clinical use anti-emesis particularly in the setting of chemotherapy or procedure Adverse effects QT prolongation serotonin syndrome headache constipation