Ondansetron is used to prevent nausea and vomiting caused by cancer chemotherapy, radiation therapy, anesthesia, and surgery.

This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.

Ondansetron comes as a tablet and in an injectable form. The tablets may be taken with or without food. The first dose of ondansetron usually is taken in a hospital or clinic 30 minutes before chemotherapy is begun. The second dose is taken 4 hours after the first dose, and the third dose is taken 8 hours after the first dose. Your doctor also may want you take one tablet every 8 hours for 1 or 2 days after chemotherapy. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take ondansetron exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Ondansetron injections are given by qualified health care professionals.

Although side effects from ondansetron are not common, they can occur. Tell your doctor if any of these symptoms are severe or do not go away:

diarrhea
headache
constipation
rash
lightheadedness
dry mouth
drowsiness
If you experience either of the following symptoms, call your doctor immediately:

difficulty breathing
chest pain

In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.

DO NOT SHARE THIS MEDICINE with others for whom it was not prescribed. DO NOT USE THIS MEDICINE for other health conditions. KEEP THIS MEDICINE out of the reach of children.

Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

This medicine is an antiemetic used to prevent nausea and vomiting following chemotherapy, radiation therapy, or surgery. It may also be used for other conditions as determined by your doctor.

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom). Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.

Before taking ondansetron,

tell your doctor and pharmacist if you are allergic to ondansetron, dolasetron (Anzemet), granisetron (Kytril), or any other drugs.
tell your doctor and pharmacist what prescription and nonprescription medications you are taking, including vitamins.
tell your doctor if you have or have ever had liver disease.
tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking ondansetron, call your doctor.