Product Description: Ondansetron is used to prevent nausea and vomiting caused by cancer chemotherapy, radiation therapy, and surgery. Ondansetron is in a class of medications called serotonin 5-HT3 receptor antagonists. It works by blocking the action of serotonin, a natural substance that may cause nausea and vomiting. Ondansetron works by blocking one of the body's natural substances (serotonin) that causes vomiting. How To Use: To prevent nausea from chemotherapy, take this medication usually within 30 minutes before treatment begins. To prevent nausea from radiation treatment, take this medication 1 to 2 hours before the start of your treatment. To prevent nausea after surgery, take ondansetron 1 hour before the start of surgery. This medication may be taken with or without food. However, your doctor may tell you not to eat before chemotherapy, radiation, or surgery. Take any other doses as directed by your doctor: Ondansetron may be taken up to 3 times a day for 1 to 2 days after your chemotherapy or radiation treatment is finished. If you are taking this medication on a prescribed schedule, take it regularly in order to get the most benefit from it. To help you remember, take it at the same times each day. Dosage is based on your medical condition and response to therapy. The dosage for children may also be based on age and weight. In patients with severe liver problems: The usual maximum dose is 8 milligrams in 24 hours. Take this medication exactly as directed. Do not take more medication or take it more often than prescribed. Ask your doctor or pharmacist if you have questions. Inform your doctor if your condition does not improve or if it worsens. Warnings And Precautions: You should not use ondansetron if: You are allergic to ondansetron or similar medicines (dolasetron, granisetron, palonosetron). To make sure ondansetron is safe for you, tell your doctor if you have: Liver disease. An electrolyte imbalance (such as low levels of potassium or magnesium in your blood). Congestive heart failure, slow heartbeats. Personal or family history of long qt syndrome. Blockage in your digestive tract (stomach or intestines). Ondansetron is not expected to harm an unborn baby. Tell your doctor if you are pregnant. It is not known whether ondansetron passes into breast milk or if it could harm a nursing baby. Tell your doctor if you are breast-feeding a baby. Ondansetron is not approved for use by anyone younger than 4 years old. Ondansetron orally disintegrating tablets may contain phenylalanine. Tell your doctor if you have phenylketonuria (PKU). Ingredients: Ondansetron 4 mg film-coated tablets