Ondansetron is a medication primarily used to prevent nausea and vomiting caused by chemotherapy, radiation therapy, or surgery. It works by blocking the action of serotonin, a natural substance in the body that can trigger these symptoms. This drug is often administered as a tablet, dissolvable film, or injection. It is generally well-tolerated, but some side effects may include headaches, dizziness, or constipation. Ondansetron is commonly prescribed in hospitals and outpatient settings to help improve the quality of life for patients undergoing treatments that may induce nausea.