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-HT3receptor antagonists. It works by blocking the action of serotonin, a natural substance that may cause nausea and vomiting.
Ondansetron comes as a tablet, a rapidly disintegrating (dissolving) tablet, and an oral solution (liquid) to take by mouth. The first dose of ondansetron is usually taken 30 minutes before the start of chemotherapy, 1 to 2 hours before the start of radiation therapy, or 1 hour before surgery. Additional doses are sometimes taken one to three times a day during chemotherapy or radiation therapy and for 1 to 2 days after the end of treatment. 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.
If you are taking the rapidly disintegrating tablet, remove the tablet from the package just before you take your dose. To open the package, do not try to push the tablet through the foil backing of the blister. Instead, use dry hands to peel back the foil backing. Gently remove the tablet and immediately place the tablet on the top of your tongue. The tablet will dissolve in a few seconds and can be swallowed with saliva.
This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.
Before taking ondansetron,
- tell your doctor and pharmacist if you are allergic to ondansetron, alosetron (Lotronex), dolasetron (Anzemet), granisetron (Kytril), palonosetron (Aloxi), any other medications, or any of the ingredients in ondansetron tablets or liquid. Ask your pharmacist for a list of the ingredients.
- tell your doctor if you are receiving apomorphine (Apokyn). Your doctor will probably tell you not to take ondansetron if you are receiving this medication.
- tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention clarithromycin (Biaxin, in Prevpac); erythromycin (E.E.S., Erythrocin, others); medications for irregular heart beat; medications for mental illness; moxifloxacin (Avelox);and tramadol (Ultram, in Ultracet).Your doctor may need to change the doses of your medications or monitor you more carefully for side effects. Many other medications may also interact with ondansetron, so be sure to tell your doctor about all the medications you are taking, even those that do not appear on this list.
- tell your doctor if you or anyone in your family has or has ever had long QT syndrome (condition that increases the risk of developing an irregular heartbeat that may cause fainting or sudden death), or another type of irregular heart beat or heart rhythm problem, or if you have or have ever had low blood levels of magnesium or potassium in your blood, congestive heart failure (CHF; condition in which the heart cannot pump enough blood to other parts of the body),or 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.
- if you have phenylketonuria (PKU, an inherited condition in which a special diet must be followed to prevent mental retardation), you should know that the orally disintegrating tablets contain aspartame that forms phenylalanine.
Unless your doctor tells you otherwise, continue your usual diet.
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.
Ondansetron may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
Some side effects can be serious. If you experience any of the following symptoms, call your doctor immediately:
- blurred vision or vision loss
- swelling of the eyes, face, lips, tongue, throat, hands, feet, ankles, or lower legs
- difficulty breathing or swallowing
- shortness of breath
- noisy, high pitched breathing
Ondansetron may cause other side effects. Call your doctor if you have any unusual problems while you are taking this medication.
Keep this medication in the container it came in, tightly closed, and out of reach of children. Store the tablets and rapidly disintegrating tablets away from light, at room temperature or in the refrigerator. Store the solution in the bottle upright at room temperature and away from light, 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.
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.
Symptoms of overdose may include:
- sudden loss of vision for a short time
- dizziness or lightheadedness
- irregular heart beat
Keep all appointments with your doctor.
Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.
It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.
AHFS® Consumer Medication Information. © Copyright, The American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.
Selected Revisions: November 15, 2011.