Used to prevent nausea and vomiting caused by cancer chemotherapy, particularly effective for delayed nausea and vomiting that occurs more than 24 hours after treatment. Also used to prevent postoperative nausea and vomiting in patients undergoing surgery. It works by blocking serotonin, a natural substance in the body that can trigger nausea and vomiting. Often preferred due to its long half-life and strong receptor binding, providing prolonged protection with a single dose.