Zuplenz

Ondansetron is a prescription medication used to prevent nausea and vomiting caused by chemotherapy or surgery. Ondansetron belongs to a group of drugs called serotonin 5-HT3 antagonists, which block serotonin, a natural chemical in the body, from causing nausea and vomiting.

This medication comes in several oral forms: tablets, orally disintegrating (dissolving) tablets, an oral soluble film, and solution (liquid). Ondansetron also comes in an intravenous (IV) form. 

The first oral 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.

Common side effects include headache, tiredness, and constipation. Ondansetron can cause dizziness. Do not drive or operate heavy machinery until you know how it affects you.

Ondansetron is a prescription medication used for the:

• prevention of nausea and vomiting associated with chemotherapy
• prevention of nausea and vomiting caused by radiation therapy
• prevention of nausea and vomiting caused by surgery 

This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.

Take ondansetron exactly as prescribed by your doctor. Follow the directions on your prescription label carefully.

Surgery

The recommended ondansetron dose for preventing nausea and vomiting after surgery is two 8 mg tablets (16 mg) taken one hour before anesthesia is administered.

Chemotherapy

High-risk (for nausea and vomiting) chemotherapy: The dose of ondansetron for high-risk chemotherapy is three 8 mg ondansetron tablets (24 mg) 30 minutes before chemotherapy.

Medium-risk (for nausea and vomiting) chemotherapy: The dose of ondansetron for medium-risk chemotherapy is ondansetron 8 mg twice daily.

• The first dose should be taken 30 minutes before chemotherapy.
• The second dose should be taken eight hours after the first dose.
• After that, ondansetron should be taken twice a day (about every 12 hours) until one to two days after chemotherapy.

​Radiation

Total body irradiation: The dose of ondansetron for total body irradiation is ondansetron 8 mg taken one to two hours before radiotherapy each day of radiation treatment.

Single high-dose fraction radiotherapy to the abdomen:The recommended dose is ondansetron 8 mg taken one to two hours before radiotherapy followed by ondansetron 8 mg every eight hours until one to two days after radiation.

Daily fractionated radiotherapy to the abdomen: The recommended dose is ondansetron 8 mg taken each day one to two hours before radiotherapy, followed by two more doses each day.

Dose in Patients with Liver Disease

The dose of ondansetron is decreased for people who have poor liver function (hepatic function). People with severely impaired liver function should not take more than 8 mg ondansetron total each day.

Serious side effects have been reported with ondansetron including:

• hypotension. Ondansetron and apomorphine (Apokyn) should not be taken at the same time as there is a risk of dangerously low blood pressure and loss of consciousness.
• severe allergic reactions. Hypersensitivity (allergic) reactions have been reported in patients who are allergic to other selective 5-HT3 receptor antagonists.
• changes in heart rhythm. ECG changes including QT interval prolongation has been seen in patients receiving ondansetron. 
• masking symptoms of intestinal blockage. Using ondansetron after abdominal surgery or chemotherapy may mask the symptoms of an intestinal blockage (abdominal ileus). 

Do not take ondansetron if you:

• are allergic to ondansetron or any ingredient in it
• are taking apomorphine (Apokyn)
• have long QT syndrome (condition that increases the risk of developing an irregular heartbeat that may cause fainting or sudden death)

Ondansetron can cause drowsiness. Do not drive or operate heavy machinery until you know how ondansetron affects you.

Ondansetron can cause serious side effects. See "Drug Precautions" section.

Common side effects include:

• headache
• tiredness
• constipation
• diarrhea
• dizziness

This is not a complete list of ondansetron side effects. Ask your doctor or pharmacist for more information.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements. Especially tell your doctor if you take:

• apomorphine (Apokyn)
• medications for irregular heart beat
• carbamazepine (Carbatrol, Epitol, Equetro, Tegretol)
• phenytoin (Dilantin, Phenytek)
• rifampicin (Rifadin)
• tramadol (Rybix, Rybix ODT, Ultram, Ultram ER)

This is not a complete list of ondansetron drug interactions. Ask your doctor or pharmacist for more information.

Tell your doctor if you are pregnant or plan to become pregnant.

The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.

Ondansetron falls into category B. There are no good studies that have been done in humans with ondansetron. But in animal studies, pregnant animals were given this medication, and the babies did not show any medical issues related to this medication.

It is not known if ondansetron, the active ingredient of ondansetron, crosses into human milk. Because many medications can cross into human milk and because of the possibility for serious adverse reactions in nursing infants with use of this medication, a choice should be made whether to stop nursing or stop the use of this medication. Your doctor and you will decide if the benefits outweigh the risk of using ondansetron.

Tell your doctor if you have phenylketonuria (PKU). The orally disintegrating tablets (ondansetron ODT) contain aspartame that forms phenylalanine.

The first oral 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.

For ondansetron orally disintegrating tablets (ODTs), you should keep each tablet in its original blister pack until you need it. Do not try to push the tablet through the foil (the tablet is delicate and would be crushed). Instead, gently peel the foil away and remove the tablet.