Ondansetron

Medically Reviewed by HaVy Ngo, Pharm.D.

Last Reviewed: Jun 15, 2022

Warnings

What are the risks of taking ondansetron hydrochloride (Zofran)?

Severe allergic reaction:
Ondansetron can cause severe allergic reactions, including anaphylaxis and bronchospasm. If you experience swelling of the face, throat or tongue, and difficulty breathing, you need to stop taking this medication and seek emergency medical attention.
QT interval prolongation and Torsade de Pointes:
Risk factors: history of QT interval prolongation; history of heart failure; low level of magnesium or potassium; taking other medications that can cause heart rhythm problems; very high doses of ondansetron (Zofran).
Very high doses of ondansetron can cause heart rhythm problems. These are heart rhythm problems that can potentially cause fast, chaotic heartbeats. If you have a heart rhythm problem, you should tell your doctor about your heart condition before taking ondansetron.
Serotonin syndrome:
Risk factors: taking other medications that affect the brain’s serotonin level, such as antidepressants, lithium, and migraine medications. Serotonin syndrome occurs when there is too much serotonin in the body; this condition is rare but can be life-threatening. You should watch out for symptoms such as fever, sweating, fast heartbeat, nausea and vomiting, agitation, and hallucinations. The risk of serotonin syndrome increases if you take ondansetron (Zofran, Zofran ODT) with other serotonergic drugs such as antidepressants, antipsychotic medicines, lithium, or migraines medications. If you experience any of these symptoms, you should stop taking ondansetron and seek emergency medical care immediately.
Masking symptoms of intestinal blockage and stomach bloating after abdominal surgery or chemotherapy:
Risk factors: Abdominal surgery; chemotherapy; history of gastrointestinal obstruction
If you just had abdominal surgery or chemotherapy, taking ondansetron (Zofran) can mask the symptoms of intestinal blockage and stomach bloating. The risk is also increased with someone with a history of gastrointestinal obstruction. Let your healthcare professional know if you notice a lack of bowel movements or flatulence.
A build-up of phenylalanine in the body:
Risk factor: History of phenylketonuria (PKU)
Phenylketonuria is a disorder where people are unable to break down and get rid of phenylalanine. The orally disintegrating tablets (ondansetron ODT, Zofran ODT) contain phenylalanine. You should let know healthcare professional know if you have PKU.

Speak to your doctor or pharmacist about other treatment options if you are at high risk for the above complications.

What should I tell my doctor before starting ondansetron hydrochloride (Zofran)?

Ondansetron is not to be used for children younger than 4 years old.

You should inform your doctor about your complete medical history, including medical conditions, allergies, pregnancy, and breastfeeding status.

Tell your doctor if you have:

Any electrolyte imbalance, such as a low level of blood potassium or magnesium.
Liver disease
Congestive heart failure
Arrhythmia (heart rhythm disorder)
Personal or family history of QT interval prolongation or Torsades de Pointes
A blockage in your digestive tract

You should not use ondansetron (Zofran) if:

You are using apomorphine (Apokyn).
You are allergic to ondansetron or other drugs in the same drug class, such as granisetron, palonosetron, dolasetron.
Taking ondansetron during early pregnancy does not appear to increase the risks of birth defects for the infant. Tell your healthcare professional if you are pregnant.

It is not known whether ondansetron is excreted into breast milk. Tell your healthcare professional if you are breastfeeding.

What proper medical care should I take while on ondansetron hydrochloride (Zofran)?

You should keep all your doctor appointments.
Ondansetron may slow your thinking or reactions; take caution if you have to drive or perform any activities that require mental alertness.
If you use liquid ondansetron, you should measure the dose carefully using an oral dosing syringe.
Do not let anyone else use your ondansetron even though they may have the same symptoms, such as nausea and vomiting.

What precautions should I take while on ondansetron hydrochloride (Zofran)?

Check your blood pressure as instructed. Ask your doctor about your goal blood pressure and when to contact them regarding an out-of-range blood pressure reading.
Visit your doctor or health care professional for regular checkups.
Do not self-treat with over-the-counter (OTC) medicines for pain, coughs, and colds while using lisinopril. Some ingredients in these medicines can increase blood pressure. Get medical advice from your doctor or pharmacist before using any OTC remedies.
Pregnant women and those who are actively trying to conceive should inform the prescribing physician.
Inform your doctor if you get severe diarrhea, nausea, and vomiting. Dehydration can increase the risk of kidney injury while taking lisinopril
Avoid salt substitutes unless advised otherwise by your doctor or health care professional.
Lisinopril can cause drowsiness or dizziness. Do not drive, operate heavy machinery, or do anything that requires you to be mentally alert until you know how lisinopril affects you.
Reduce or limit alcohol intake while taking lisinopril

What drugs can interact with ondansetron hydrochloride (Zofran)?

Tell your doctor and pharmacist all of the medications you are taking or have recently stopped. Certain medications, when used at the same time with ondansetron, can cause drug interactions that increase the risk of heart rhythm problems (arrhythmia); let your doctor know if you are taking any of the following medications:

Antibiotics - macrolide antibiotics such as azithromycin, clarithromycin, erythromycin.
Heart rhythm medicines - amiodarone, quinidine, sotalol, dofetilide, pimozide, procainamide.
Antidepressants
Antipsychotic medicines
Medicines to treat cancer, HIV, or AIDS

Taking ondansetron with serotonergic drugs (drugs that affect the level of serotonin) can cause serotonin syndrome, where there is a high level of serotonin built-up in the body. Tell your doctor if you are taking any of the following medication classes:

Antidepressants
Antipsychotics
Medicines for nausea and vomiting
Narcotic pain medications

This is not a complete list. Other drugs, including prescriptions, over-the-counter medicines, herbal products, and vitamins, may interact with ondansetron (Zofran, Zofran ODT). Not all potential drug interactions are listed in this guide. It is highly recommended to keep a list of all the drug products you are using (prescriptions, over-the-counter products, herbal supplements, natural products, and vitamins) and share it with your doctor and pharmacist.

Find the best discount on Ondansetron »