Ondansetron, marketed under the brand name Zofran, is a blocks the actions of chemicals in the body that can trigger nausea and vomiting. Ondansetron is used to prevent nausea and vomiting that may be caused by surgery, cancer chemotherapy, or radiation treatment. Ondansetron may be used for purposes not listed in this medication guide.

Ondansetron precautions. Before taking ondansetron, tell your doctor or pharmacist if you are allergic to it; or to other anti-nausea serotonin blockers (e.g., granisetron); or if you have any other allergies. Before using this medication, tell your doctor or pharmacist your medical history, especially of: irregular heartbeat, liver disease, stomach/intestinal problems (e.g., recent abdominal surgery, ileus, swelling).