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Important Safety Information

Ondansetron is a prescription infusion medication that blocks the chemicals in the brain that trigger feeling nauseous and vomiting. Therefore, it is an ideal form of treatment for patients who are undergoing chemotherapy or radiation, as well as for individuals who experience nausea and vomiting due to surgery. Ondansetron is not approved for patients who are younger than four years of age.

Ondansetron may impair thinking and reaction times. Therefore, avoid driving and/or operating heavy machinery after treatment.

Prior to starting treatment, tell your doctor about all medications you’re currently taking — including prescription, over-the-counter, herbal supplements, and vitamins. Some medications may interfere with Ondansetron, especially if you are undergoing treatment with any of the following drugs:

  • Apomorphine (Apokyn)
  • Carbamazepine (Carbatrol, Epitol, Equetro, Tegretol)
  • Phenytoin (Dilantin)
  • Clarithromycin (Biaxin)
  • Erythromycin (E.E.S.)
  • Fentanyl (Abstral, Actiq, Duragesic, Fentora, Lazanda, Onsolis, Subsys)
  • Lithium (Lithobid)
  • Almotriptan (Axert)
  • Eletriptan (Relpax)
  • Frovatriptan (Frova)
  • Naratriptan (Amerge)
  • Rizatriptan (Maxalt)
  • Sumatriptan (Imitrex)
  • Zolmitriptan (Zomig)
  • Methylene Blue
  • Mirtazapine (Remeron)
  • Monoamine oxidase (MAO)
  • Isocarboxazid (Marplan)
  • Linezolid (Zyvox)
  • Phenelzine (Nardil)
  • Selegiline (Eldepryl, Emsam, Zelapar)
  • Tranylcypromine (Parnate)
  • Moxifloxacin (Avelox)
  • Serotonin reuptake inhibitors
  • Medications used to treat irregular heartbeat, mental illness, and/or migraines

Also, ask your pharmacist for a list of ingredients and discuss with your medical provider if you are allergic to any of them. Your provider may be able to suggest alternatives.

Ondansetron should not harm an unborn baby. However, talk to your doctor if you’re pregnant or planning on becoming pregnant. It is unknown whether Ondansetron can pass through your child through breast milk. Therefore, discuss feeding options with your healthcare provider.

What is the most important information I should know about Ondansetron?

Talk to your doctor about your medical history, as well as your family’s medical history — especially if you or a family member has had long QT syndrome, any other type of issues with irregular heartbeats, heart failure, liver disease, or low blood levels of magnesium or potassium. If you have phenylketonuria (PKU), you will have to follow a special diet to prevent mental retardation.

Ondansetron may cause serotonin buildup in your body, which could be fatal. There’s a higher risk of serotonin syndrome if you are currently taking medications to treat depression or a psychiatric disorder.

Side Effects of Ondansetron

As with any prescription medication, Ondansetron carries the risk of side effects. The most common ones include:

  • Headaches
  • Drowsiness
  • Chills
  • Tiredness
  • Constipation
  • Diarrhea

In rare cases, a patient may experience more serious side effects. Seek emergency medical care immediately if you experience any of the following symptoms:

  • Confusion
  • Breathing difficulties
  • Chest pain
  • Irregular heartbeat
  • Blurred vision
  • Vision loss
  • Skin rash
  • Hives
  • Itching
  • Swelling of the eyes, face, lips, tongue, and/or throat
  • Swelling of the ankles and/or feet
  • Hallucinations
  • Excessive sweating
  • Loss of coordination
  • Severe constipation
  • Jaundice (yellowing of the skin or eyes)
  • Twitching muscles
  • Seizures
  • Loss of consciousness

Tell your doctor if you experience any negative side effects. You are also encouraged to report such side effects to the Food and Drug Administration (FDA) by visiting www.fda.gov/medwatch, or by calling 1-800-FDA-1088.


Ondansetron is used to treat nausea and vomiting due to cancer treatments and/or surgery. The dosage will depend on the patient’s medical condition — as well as on their age and weight. Modifications may be necessary for patients with severe liver problems.

Please refer to the full prescribing information.