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Zofran (injection)

Generic name: ondansetron (injection) [ on-DAN-se-tron ]
Brand name: Zofran injection
Drug class: 5HT3 receptor antagonists

Medically reviewed by Drugs.com on Aug 4, 2023. Written by Cerner Multum.

The Zofran brand name has been discontinued in the U.S. If generic versions of this product have been approved by the FDA, there may be generic equivalents available.

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 or by medicine to treat cancer (chemotherapy).

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

Ondansetron side effects

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

Zofran may cause serious side effects. Call your doctor at once if you have:

Common side effects of Zofran may include:

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.

Zofran side effects (more detail)

Warnings

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

Before taking this medicine

You should not use this medicine if you are allergic to ondansetron, or if you are also using apomorphine (Apokyn).

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

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.

How is ondansetron given?

Ondansetron is injected into a vein through an IV. A healthcare provider will give you this injection.

Ondansetron is usually given just before your surgery begins, or within 2 hours after surgery.

To prevent nausea and vomiting caused by chemotherapy, ondansetron is given 30 minutes before the start of chemotherapy. A second and third dose of ondansetron are sometimes given 4 hours and 8 hours after the first dose.

Detailed Zofran dosage information

What happens if I miss a dose?

Because you will receive ondansetron in a clinical setting, you are not likely to miss a dose.

What happens if I overdose?

Since this medicine is given by a healthcare professional in a medical setting, an overdose is unlikely to occur.

What should I avoid after receiving ondansetron?

This medicine may cause blurred vision and may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert and able to see clearly.

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.

Receiving 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:

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.

Zofran drug interactions (more detail)

Popular FAQ

Although ondansetron is not specifically approved by the FDA to treat nausea and vomiting during pregnancy (NVP), its use is common, and approximately 25% of pregnant women are prescribed ondansetron to treat NVP. Overall, studies show the use of ondansetron appears to be associated with an additional 3 instances of oral cleft defects (such as cleft lip or cleft palate) for every 10,000 women exposed to ondansetron during their first trimester. There may also be a very slight increased risk of a type of heart defect called a ventricular septal defect, but no apparent increased risk of other birth defects, miscarriage, or fetal death. Continue reading

If you are taking ondansetron for nausea that occurs with meals, then the standard tablet should be taken half an hour to 1 hour before meals, and the orally disintegrating tablet or oral soluble film can be taken 15 minutes before meals. However, if you are taking ondansetron for constant, all day nausea then it should be taken at regular intervals during the day as prescribed, with or without food.

You can take ondansetron more frequently initially, for example, if you are taking it to prevent or treat nausea of vomiting from chemotherapy you can take 4mg then follow up with another 4mg dose at 4 and 8 hours after the first dose. The following day you should only take it every 8 hours (3 times a day). If you continue taking ondansetron more frequently than this you are at higher risk of side effects such as constipation, headache, or heart effects.

Oral ondansetron works quickly, usually within 30 minutes, but it can take up to two hours for the full effect. It’s taken before you receive medicines or procedures that might make you feel nauseous or cause vomiting. Oral doses are usually taken 30 minutes before chemotherapy, 1 hour before surgery, or 1 to 2 hours before radiation treatments. You may need extra doses. Your doctor will tell you exactly when to take your medication.

Yes, ondansetron (Zofran) might make you feel sleepy or tired. Ondansetron injection for the treatment of post-operative nausea and vomiting has been reported to cause drowsiness or sedation in 8% of patients vs. 7% of those using a placebo (an inactive treatment). Malaise (generally feeling unwell) and fatigue (tiredness or lack of energy) have also been reported in 13% of patients (vs. 2% placebo) when it is used orally for the prevention of chemotherapy-induced nausea and vomiting.

Further information

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

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

Medical Disclaimer

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