Ondansetron | Side Effects, Dosage, Uses, And More - Healthline

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Medically reviewed by Femi Aremu, PharmD — Written by University of Illinois — Updated on August 5, 2021

Important warnings
About
Side effects
Interactions
Other warnings
Dosage
Take as directed
Important considerations
Alternatives

Highlights for ondansetron

Ondansetron orally disintegrating tablet is available as a brand-name drug and as a generic drug. Brand name: Zofran ODT.
Ondansetron comes in three forms that you take by mouth: a tablet, a disintegrating tablet, and a solution. It’s also available in an intravenous (IV) form. This form is only given by a healthcare professional.
Ondansetron orally disintegrating tablet is used to prevent nausea and vomiting caused by certain medical treatments.

Important warnings

Serotonin syndrome warning: Ondansetron raises your risk of a life-threatening condition called serotonin syndrome. This syndrome occurs when the chemical serotonin builds up too much in your body. A high level of serotonin can cause agitation, delirium (confused thinking) and hallucinations (seeing or hearing things that aren’t real). It can also cause sweating, rapid heartbeat, muscle stiffness, tremor, seizures, jerky muscle movements, and coma. Call your doctor right away if you have any of these symptoms. This condition can result from using ondansetron alone. However, it’s more likely to occur when you’re also taking another drug that affects serotonin levels.

What is ondansetron?

Ondansetron is a prescription drug. It comes in three forms that you take by mouth: a tablet, a disintegrating tablet, and a solution. It’s also available in an intravenous (IV) form, which is only given by a healthcare professional.

Ondansetron orally disintegrating tablet is available as the brand-name drug Zofran ODT. It’s also available as a generic drug. Generic drugs usually cost less than the brand-name version. In some cases, they may not be available in every strength or form as the brand-name drug.

Ondansetron may be used as part of a combination therapy. This means you may need to take it with other medications.

Why it’s used

Ondansetron orally disintegrating tablet is used to prevent nausea and vomiting caused by certain medical treatments. These treatments include:

chemotherapy
radiation treatment
surgery

How it works

Ondansetron belongs to a class of drugs called antiemetics. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions. Antiemetics are drugs that reduce nausea and vomiting.

Ondansetron works by blocking the release of the chemical serotonin in the gut and the central nervous system. This keeps serotonin from causing nausea and vomiting.

Ondansetron side effects

Ondansetron orally disintegrating tablet may cause drowsiness. It can also cause other side effects.

More common side effects

The more common side effects of ondansetron can include:

headache
diarrhea
constipation
dizziness
drowsiness

If these effects are mild, they may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious side effects

Call your doctor right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

Serotonin syndrome. Symptoms can include:
- agitation
- hallucinations (seeing or hearing things that aren’t real)
- rapid heartbeat
- sweating
- feeling hot
- muscle rigidity (stiffness)
- tremor
- nausea
- vomiting
- diarrhea
- coma

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare professional who knows your medical history.

Ondansetron may interact with other medications

Ondansetron orally disintegrating tablet can interact with other medications, vitamins, or herbs you may be taking. An interaction is when a substance changes the way a drug works. This can be harmful or prevent the drug from working well.

To help avoid interactions, your doctor should manage all of your medications carefully. Be sure to tell your doctor about all medications, vitamins, or herbs you’re taking. To find out how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Examples of drugs that can cause interactions with ondansetron are listed below.

Drugs you should not use with ondansetron

Do not take these drugs with ondansetron. Doing so can cause dangerous effects in your body. Examples of these drugs include:

Apomorphine. Taking this drug with ondansetron can cause your blood pressure to drop to unsafe levels. This can cause you to pass out.

Interactions that increase your risk of side effects from ondansetron

Taking ondansetron with certain medications raises your risk of side effects from ondansetron. This is because the amount of ondansetron in your body may be increased. Examples of these drugs include:

Other drugs that affect serotonin levels, such as fluoxetine and paroxetine.

Interactions that can make ondansetron less effective

Taking these drugs with ondansetron can make ondansetron less effective. This is because the amount of ondansetron in your body may be decreased. Examples of these drugs include:

Anti-seizure drugs, such as phenytoin or carbamazepine. Your doctor may switch you from ondansetron to a different drug if needed.
Tuberculosis drugs, such as rifampin, rifabutin, or rifapentine. Your doctor may switch you from ondansetron to a different drug if needed.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare professional about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.

Ondansetron warnings

This drug comes with several warnings.

Allergy warning

Ondansetron can cause a severe allergic reaction. Symptoms can include:

flushing
trouble breathing
swelling of your throat or tongue
dizziness
coughing

If you develop these symptoms, call 911 or go to the nearest emergency room.

Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could be fatal (cause death).

Warnings for people with certain health conditions

For people with risk factors for heart arrhythmias: If you have conditions such as heart failure or congenital long QT syndrome, this drug may increase your risk of arrhythmias. Ask your doctor if you have risk factors for arrhythmias.

For people with phenylketonuria: The ondansetron orally disintegrating tablet contains phenylalanine. This amino acid can cause dangerous effects in people with a condition called phenylketonuria. Don’t take the orally disintegrating tablet if you have phenylketonuria.

Warnings for other groups

For pregnant women: There haven’t been enough studies done in humans to be certain how ondansetron might affect a fetus when the mother takes it. Research in animals has not shown a risk to the fetus. However, animal studies do not always predict the way humans would respond.

Talk to your doctor if you’re pregnant or planning to become pregnant. This drug should only be used in pregnancy if clearly needed.

For women who are breastfeeding: Ondansetron may pass into breast milk and may cause side effects in a child who is breastfed. Talk to your doctor if you breastfeed your child. You may need to decide whether to stop breastfeeding or stop taking this medication.

For seniors: The kidneys of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, a higher amount of a drug stays in your body for a longer time. This raises your risk of side effects.

For children: This medication has not been studied in children younger than 4 years. It should not be used in children of this age range.

How to take ondansetron

All possible dosages and drug forms may not be included here. Your dosage, drug form, and how often you take the drug will depend on:

your age
the condition being treated
how severe your condition is
other medical conditions you have
how you react to the first dose

Drug forms and strengths

Generic: Ondansetron

Form: orally disintegrating tablet
Strengths: 4 mg, 8 mg

Brand: Zofran ODT

Form: orally disintegrating tablet
Strengths: 4 mg, 8 mg
Dosage for prevention of nausea and vomiting caused by chemotherapy

Adult dosage (ages 18–64 years)

Typical dosage for chemotherapy that’s highly likely to cause nausea and vomiting: A single 24-mg dose given 30 minutes before chemotherapy.
Typical dosage for chemotherapy that’s somewhat likely to cause nausea and vomiting: 8 mg, 30 minutes before chemotherapy. Eight hours later, you can take another 8 mg. For 1–2 days after chemotherapy, you can take 8 mg twice per day.

Child dosage (ages 12–17 years)

Typical dosage for chemotherapy that’s somewhat likely to cause nausea and vomiting: 8 mg given 30 minutes before chemotherapy. Four and eight hours after the first dose, your child can take another 8 mg. For 1–2 days after chemotherapy, they can take 8 mg three times per day.

Child dosage (ages 4–11 years)

Typical dosage for chemotherapy that’s somewhat likely to cause nausea and vomiting: 4 mg given 30 minutes before chemotherapy. Four and eight hours after the first dose, your child can take another 4 mg. For 1–2 days after chemotherapy, your child can take 4 mg, three times per day.

Child dosage (ages 0–3 years)

It has not been confirmed that ondansetron is safe and effective for use in children younger than 4 years. It should not be used in children of this age range.

Senior dosage (ages 65 years and older)

The kidneys of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, a higher amount of a drug stays in your body for a longer time. This raises your risk of side effects.

Your doctor may start you on a lowered dosage or a different dosing schedule. This can help keep levels of this drug from building up too much in your body.

Dosage for prevention of nausea and vomiting caused by radiation treatment

Adult dosage (ages 18–64 years)

Typical dosage: 8 mg starting 1–2 hours before radiation, followed by 8-mg doses every 8 hours after that first dose. Continue for 1 to 2 days after you complete radiation treatment. This dosage may vary depending on the type of radiation you receive.

Child dosage (ages 0–17 years)

It has not been established that this drug is safe and effective for this use in children.

Senior dosage (ages 65 years and older)

Your doctor may start you on a lowered dosage or a different dosing schedule. This can help keep levels of this drug from building up too much in your body.

Dosage for prevention of nausea and vomiting caused by surgery

Adult dosage (ages 18–64 years)

Typical dosage: 16 mg one hour before you receive anesthesia for surgery.

Child dosage (ages 0–17 years)

It has not been established that this drug is safe and effective for this use in children.

Senior dosage (ages 65 years and older)

Your doctor may start you on a lowered dosage or a different dosing schedule. This can help keep levels of this drug from building up too much in your body.

Special dosage considerations

For people with liver disease: If you have severe liver disease, you should not take more than 8 mg of ondansetron per day.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always speak with your doctor or pharmacist about dosages that are right for you.

Take as directed

Ondansetron orally disintegrating tablet is used for short-term treatment. It comes with serious risks if you don’t take it as prescribed.

If you stop taking the drug suddenly or don’t take it at all: You could have nausea and vomiting that’s not controlled.

If you take too much: You could have dangerous levels of the drug in your body. Symptoms of an overdose of this drug can include:

faintness
drowsiness
agitation
fast heartbeat
flushing (sudden reddening of the skin)
seizures

If you think you’ve taken too much of this drug, call your doctor or local poison control center. If your symptoms are severe, call 911 or go to the nearest emergency room right away.

How to tell if the drug is working: You should not have nausea or vomiting. If you do, it should be less severe.

Important considerations for taking ondansetron

Keep these considerations in mind if your doctor prescribes ondansetron for you.

General

You can take ondansetron with or without food.
Take this drug at the time(s) recommended by your doctor.
Do not cut or crush the orally disintegrating tablets.

Storage

Store the orally disintegrating tablets at a temperature between 36°F and 86°F (2°C and 30°C).
Keep this drug away from light.
Don’t store this medication in moist or damp areas, such as bathrooms.

Refills

A prescription for this medication is refillable. You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.

Travel

When traveling with your medication:

Always carry your medication with you. When flying, never put it into a checked bag. Keep it in your carry-on bag.
Don’t worry about airport X-ray machines. They can’t harm your medication.
You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled container with you.
Don’t put this medication in your car’s glove compartment or leave it in the car. Be sure to avoid doing this when the weather is very hot or very cold.

Self-management

When taking the orally disintegrating tablet out of its package, peel the foil back. Don’t try to push the tablet through the foil. This step will help keep the tablet from breaking.
Place the tablet on your tongue. Leave it there for a few seconds to allow it to dissolve, and then swallow. You don’t need to take the tablet with liquid.

Availability

Not every pharmacy stocks this drug. When filling your prescription, be sure to call ahead to make sure your pharmacy carries it.

Are there any alternatives?

There are other drugs available to treat your condition. Some may be better suited for you than others. Talk to your doctor about other drug options that may work for you.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.

Ondansetron, orally disintegrating solid images

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How we reviewed this article:

SourcesHistoryHealthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Ondansetron hydrochloride - ondansetron solution. (2017).https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=fa8c2931-35a7-4b4b-8be2-eda701b51079&type=display
Ondansetron hydrochloride tablet, film coated; Ondansetron tablet, orally disintegrating. (2021).https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=92c758a3-e749-4a15-be4b-ee30b364b2b0
Zofran - ondansetron hydrochloride tablet, film coated. (2021).https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=555f81bc-4ce0-4f77-b394-b974838c4440&type=display#

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Medically reviewed by Femi Aremu, PharmD — Written by University of Illinois — Updated on August 5, 2021

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Important warnings

What is ondansetron?

Why it’s used

How it works

Ondansetron side effects

More common side effects

Serious side effects

Ondansetron may interact with other medications

Drugs you should not use with ondansetron

Interactions that increase your risk of side effects from ondansetron

Interactions that can make ondansetron less effective

Ondansetron warnings

Allergy warning

Warnings for people with certain health conditions

Warnings for other groups

How to take ondansetron

Drug forms and strengths

Dosage for prevention of nausea and vomiting caused by radiation treatment

Dosage for prevention of nausea and vomiting caused by surgery

Special dosage considerations

Take as directed

Important considerations for taking ondansetron

General

Storage

Refills

Travel

Self-management

Availability

Are there any alternatives?

Ondansetron, orally disintegrating solid images

How we reviewed this article:

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