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What is ondansetron?

Ondansetron (also called Zofran®) is used to prevent and treat nausea and vomiting caused by chemotherapy, radiation, or surgery. Ondansetron is available in these forms taken by mouth:

  • A 4 mg and 8 mg tablet
  • A clear liquid
  • A disintegrating round white tablet (called ondansetron ODT), available in 4 mg and 8 mg strengths, that dissolve on the tongue

Ondansetron is also available as a clear liquid given by vein (IV).

Laboratory testing for ondansetron

An enzyme in the body called cytochrome P450 2D6 (CYP2D6) has the ability to break down certain medicines including ondansetron. A genetic test can be done to determine if your CYP2D6 breaks down some medicines slower or faster than normal. If your body breaks down medicines faster than normal, you should avoid taking ondansetron because it might not work well for you. For information about CYP2D6 and its effect on ondansetron, talk with your doctor or pharmacist, and see “Do you know… Cytochrome P450 2D6 (CYP2D6) and medicines.” For more details, go to

Possible side effects of ondansetron

  • Headache
  • Pain in the abdomen
  • Diarrhea or constipation
  • Feeling tired
  • Blurred vision
  • Rash
  • Feeling dizzy
  • Temporary changes in liver function

These are the most common side effects, but there may be others. Please report all side effects to the doctor or nurse.

In case of a severe side effect or reaction, call the doctor, nurse, or pharmacist at 901-595-3300. If you are outside the Memphis area, dial toll-free 1-866-2STJUDE (1-866-278-5833), and press 0 once the call is connected.

Special instructions for ondansetron

  • If you have headaches while taking ondansetron, your doctor may tell you take acetaminophen (Tylenol®) for the pain.
  • If you are taking the tablet (ODT) that dissolves on the tongue, do not try to push the tablet through the foil backing. Instead, with dry hands, peel off the foil and gently remove the tablet. Place the tablet on the top of your tongue right away where it will dissolve in seconds. Then swallow your saliva. You do not need liquid in your mouth when you are taking this form of ondansetron.
  • Ondansetron usually controls nausea and vomiting for as long as 8 hours. If you have nausea or vomiting between ondansetron doses (sometimes called “breakthrough” nausea or vomiting), tell your doctor, nurse, or clinical pharmacist. Another medicine may be needed to control your breakthrough nausea or vomiting.
  • Store ondansetron tablets and liquid at room temperature in a dry place.


This document is not intended to take the place of the care and attention of your personal physician or other professional medical services. Our aim is to promote active participation in your care and treatment by providing information and education. Questions about individual health concerns or specific treatment options should be discussed with your physician.

St. Jude complies with health care-related federal civil rights laws and does not discriminate on the basis of race, color, national origin, age, disability, or sex.

ATTENTION: If you speak another language, assistance services, free of charge, are available to you. Call 1-866-278-5833 (TTY: 1-901-595-1040).

ATENCIÓN: si habla español, tiene a su disposición servicios gratuitos de asistencia lingüística. Llame al 1-866-278-5833 (TTY: 1-901-595-1040).

تنبيه: إذا كنت تتحدث باللغة العربية فيمكنك الاستعانة بخدمات المساعدة اللغوية المتوفرة لك مجانا. .يرجى الاتصال بالرقم. 5833-278-866-1  (الهاتف النصي: 1040-595-901-1).