Ondansetron is a medicine given to children to help treat nausea and vomiting. It is mainly given to treat nausea and vomiting associated with surgery, chemotherapy, radiotherapy, and stomach/intestinal infection. It also helps treat vomiting that is caused as a side effect of medicines like painkillers. Ondansetron may be given before or after meals. To control vomiting caused due to chemotherapy, give this medicine to your child 30 minutes before the procedure. Give it 1 to 2 hours before a radiotherapy session and 1 hour before surgery to prevent your child from vomiting post these procedures. If your child expels out the medicine within 30 minutes of the intake, help your child calm down and repeat the dose. Do not double dose if it is already time for the next dose.