Generic name: ondansetron (oral) [ on-DAN-se-tron ]
Brand names: Zofran, Zofran ODT, Zuplenz
Drug class: 5HT3 receptor antagonists

Medically reviewed by Philip Thornton, DipPharm. Last updated on Aug 13, 2023.

What is ondansetron?

Ondansetron blocks the actions of chemicals in the body that can trigger nausea and vomiting.

Ondansetron is used to prevent nausea and vomiting that may be caused by surgery, cancer chemotherapy, or radiation treatment.

Ondansetron may be used for purposes not listed in this medication guide.

Warnings

You should not use ondansetron if you are also using apomorphine (Apokyn).

You should not use ondansetron if you are allergic to it or to similar medicines such as dolasetron (Anzemet), granisetron (Kytril), or palonosetron (Aloxi).

Before taking ondansetron, tell your doctor if you have liver disease, or a personal or family history of Long QT syndrome.

Ondansetron orally disintegrating tablets may contain phenylalanine. Tell your doctor if you have phenylketonuria (PKU).

Serious side effects of ondansetron include blurred vision or temporary vision loss (lasting from only a few minutes to several hours), slow heart rate, trouble breathing, anxiety, agitation, shivering, feeling like you might pass out, and urinating less than usual or not at all. Stop taking this medicine and call your doctor at once if you have any of these side effects. Ondansetron may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.

Before taking ondansetron

You should not use ondansetron if:

• you are also using apomorphine (Apokyn); or

• you are allergic to ondansetron or similar medicines (dolasetron, granisetron, palonosetron).

To make sure ondansetron is safe for you, tell your doctor if you have:

• liver disease;

• an electrolyte imbalance (such as low levels of potassium or magnesium in your blood);

• congestive heart failure, slow heartbeats;

• a personal or family history of long QT syndrome; or

• a blockage in your digestive tract (stomach or intestines).

Ondansetron is not expected to harm an unborn baby. Tell your doctor if you are pregnant.

It is not known whether ondansetron passes into breast milk or if it could harm a nursing baby. Tell your doctor if you are breast-feeding a baby.

Ondansetron is not approved for use by anyone younger than 4 years old.

Ondansetron orally disintegrating tablets may contain phenylalanine. Tell your doctor if you have phenylketonuria (PKU).

How should I take ondansetron?

Take ondansetron exactly as prescribed by your doctor. Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

Ondansetron can be taken with or without food.

The first dose is usually taken before the start of your surgery, chemotherapy, or radiation treatment. Follow your doctor's dosing instructions very carefully.

Take the ondansetron regular tablet with a full glass of water.

To take the orally disintegrating tablet (Zofran ODT):

• Keep the tablet in its blister pack until you are ready to take it. Open the package and peel back the foil. Do not push a tablet through the foil or you may damage the tablet.

• Use dry hands to remove the tablet and place it in your mouth.

• Do not swallow the tablet whole. Allow it to dissolve in your mouth without chewing.

• Swallow several times as the tablet dissolves.

To use ondansetron oral soluble film (strip) (Zuplenz):

• Keep the strip in the foil pouch until you are ready to use the medicine.

• Using dry hands, remove the strip and place it on your tongue. It will begin to dissolve right away.

• Do not swallow the strip whole. Allow it to dissolve in your mouth without chewing.

• Swallow several times after the strip dissolves. If desired, you may drink liquid to help swallow the dissolved strip.

• Wash your hands after using Zuplenz.

Measure liquid medicine with the dosing syringe provided, or with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.

Store at room temperature away from moisture, heat, and light. Store liquid medicine in an upright position.

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include sudden loss of vision, severe constipation, feeling light-headed, or fainting.

What to avoid

Ondansetron may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.

Ondansetron side effects

Get emergency medical help if you have signs of an allergic reaction to ondansetron: rash, hives; fever, chills, difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

• severe constipation, stomach pain, or bloating;

• headache with chest pain and severe dizziness, fainting, fast or pounding heartbeats;

• fast or pounding heartbeats;

• jaundice (yellowing of the skin or eyes);

• blurred vision or temporary vision loss (lasting from only a few minutes to several hours);

• high levels of serotonin in the body--agitation, hallucinations, fever, fast heart rate, overactive reflexes, nausea, vomiting, diarrhea, loss of coordination, fainting.

Common ondansetron side effects may include:

• diarrhea or constipation;

• headache;

• drowsiness; or

• tired feeling.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Dosing information

Usual Adult Dose of Ondansetron for Nausea/Vomiting -- Chemotherapy Induced:

Oral:
Highly Emetogenic Cancer Chemotherapy (HEC):
-Recommended dose: 24 mg orally 30 minutes before the start of single-day HEC (including cisplatin doses of 50 mg/m2 or greater)

Moderately Emetogenic Cancer Chemotherapy (MEC):
-Recommended dose: 8 mg orally twice a day, with the first dose administered 30 minutes before the start of chemotherapy and the subsequent dose 8 hours later; then 8 mg orally 2 times a day (every 12 hours) for 1 to 2 days after the completion of chemotherapy

Parenteral:
-Recommended dose: 0.15 mg/kg IV, with the first dose (infused over 15 minutes) 30 minutes before the start of emetogenic chemotherapy and subsequent doses given 4 and 8 hours after the first dose.
-Maximum dose: 16 mg per dose

Comments:
-Multi-day, single-dose administration of 24 mg orally for HEC has not been studied.
-The injection formulation should be diluted prior to IV administration.

Uses:
-Prevention of nausea and vomiting associated with HEC or MEC
-Prevention of nausea and vomiting associated with initial and repeat courses of emetogenic chemotherapy

Usual Adult Dose of Ondansetron for Nausea/Vomiting:

Oral:
Highly Emetogenic Cancer Chemotherapy (HEC):
-Recommended dose: 24 mg orally 30 minutes before the start of single-day HEC (including cisplatin doses of 50 mg/m2 or greater)

Moderately Emetogenic Cancer Chemotherapy (MEC):
-Recommended dose: 8 mg orally twice a day, with the first dose administered 30 minutes before the start of chemotherapy and the subsequent dose 8 hours later; then 8 mg orally 2 times a day (every 12 hours) for 1 to 2 days after the completion of chemotherapy

Parenteral:
-Recommended dose: 0.15 mg/kg IV, with the first dose (infused over 15 minutes) 30 minutes before the start of emetogenic chemotherapy and subsequent doses given 4 and 8 hours after the first dose.
-Maximum dose: 16 mg per dose

Comments:
-Multi-day, single-dose administration of 24 mg orally for HEC has not been studied.
-The injection formulation should be diluted prior to IV administration.

Uses:
-Prevention of nausea and vomiting associated with HEC or MEC
-Prevention of nausea and vomiting associated with initial and repeat courses of emetogenic chemotherapy

Usual Adult Dose of Ondansetron for Nausea/Vomiting -- Postoperative:

Oral:
-Recommended dose: 16 mg orally 1 hour before the induction of anesthesia

Parenteral:
-Recommended dose: 4 mg IV (undiluted) immediately before induction of anesthesia or postoperatively (nausea and/or vomiting within 2 hours after surgery)
-Alternative route: 4 mg IM (undiluted)

Comment:
-Administration of a second dose does not provide additional control of nausea and vomiting.

Use:
-Prevention of postoperative nausea and vomiting

Usual Adult Dose for Nausea/Vomiting--Radiation Induced:

Recommended dose: 8 mg orally 3 times a day
-Total Body Irradiation: 8 mg orally 1 to 2 hours before each fraction of radiotherapy administered each day
-Single High-dose Fraction Radiotherapy to the Abdomen: 8 mg orally 1 to 2 hours before radiotherapy, with subsequent doses every 8 hours after the first dose for 1 to 2 days after the completion of radiotherapy
-Daily Fractionated Radiotherapy to the Abdomen: 8 mg orally 1 to 2 hours before radiotherapy, with subsequent doses every 8 hours after the first dose for each day radiotherapy is given

Use:
-Prevention of nausea and vomiting associated with radiotherapy, either as total body irradiation, single high-dose fraction, or daily fractions to the abdomen

Usual Pediatric Dose for Nausea/Vomiting -- Postoperative:

Parenteral:
1 month to 12 years:
Less than 40 kg:
-Recommended dose: 0.1 mg/kg IV over 2 to 5 minutes immediately prior to/following anesthesia induction or postoperatively (nausea and/or vomiting occurring shortly after surgery)

40 kg and greater:
-Recommended dose: 4 mg IV over 2 to 5 minutes immediately prior to/following anesthesia induction or postoperatively (nausea and/or vomiting occurring shortly after surgery)

Use:
-Prevention of postoperative nausea and vomiting

Usual Pediatric Dose for Nausea/Vomiting -- Chemotherapy Induced:

Oral:
4 to 11 years:
-Recommended dose: 4 mg orally 3 times a day, with the first dose administered 30 minutes before the start of chemotherapy, and subsequent doses 4 and 8 hours after the first dose; then 4 mg orally 3 times a day (every 8 hours) for 1 to 2 days after the completion of chemotherapy

12 years and older:
-Recommended dose: 8 mg orally twice a day, with the first dose administered 30 minutes before the start of chemotherapy and the subsequent dose 8 hours later; then 8 mg orally 2 times a day (every 12 hours) for 1 to 2 days after the completion of chemotherapy

Parenteral:
6 months to 18 years:
-Recommended dose: 0.15 mg/kg IV, with the first dose (infused over 15 minutes) 30 minutes before the start of emetogenic chemotherapy, and subsequent doses given 4 and 8 hours after the first dose
-Maximum dose: 16 mg (per dose)

Comments:
-The injection formulation should be diluted in 50 mL prior to IV administration.
-This drug should be used to prevent nausea and vomiting associated with moderately to highly emetogenic chemotherapy.

Uses:
-Prevention of nausea and vomiting associated with moderately emetogenic cancer chemotherapy
-Prevention of nausea and vomiting associated with initial and repeat courses of emetogenic chemotherapy

Related/similar drugs

hydroxyzine, ondansetron, lorazepam, olanzapine, meclizine, dexamethasone, Zofran, promethazine, metoclopramide, Ativan

What other drugs will affect ondansetron?

Ondansetron can cause a serious heart problem, especially if you use certain medicines at the same time, including antibiotics, antidepressants, heart rhythm medicine, antipsychotic medicines, and medicines to treat cancer, malaria, HIV or AIDS. Tell your doctor about all medicines you use, and those you start or stop using during your treatment with ondansetron.

Taking ondansetron while you are using certain other medicines can cause high levels of serotonin to build up in your body, a condition called "serotonin syndrome," which can be fatal. Tell your doctor if you also use:

• medicine to treat depression;

• medicine to treat a psychiatric disorder;

• a narcotic (opioid) medication; or

• medicine to prevent nausea and vomiting.

This list is not complete and many other drugs can interact with ondansetron. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Give a list of all your medicines to any healthcare provider who treats you.

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Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use ondansetron only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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