Active Ingredient

Ondansetron

Ondansetron is a medication used to prevent nausea and vomiting. It is often prescribed for patients undergoing certain medical treatments that can cause these symptoms.

It works by blocking the actions of chemicals in the body that can trigger nausea and vomiting. It is commonly used in clinical settings to improve patient comfort.

Written By Douglas C. Goldberg, MD

Reviewed By Philip Schein, MD

Last Updated 28 Nov 2025

Available Ondansetron Brands

Zofran

Strengths 4mg, 8mg

Ondansetron Uses

Ondansetron is primarily used to manage and prevent nausea and vomiting associated with certain medical conditions and treatments.

Nausea and vomiting caused by chemotherapy
Postoperative nausea and vomiting
Radiotherapy-induced nausea and vomiting
Prevention of nausea and vomiting in some medical procedures

How Ondansetron Works

Ondansetron belongs to a class of drugs known as antiemetics. It works by blocking serotonin, a natural substance in the body that can cause nausea and vomiting.

By inhibiting serotonin receptors in the brain and gut, ondansetron helps to prevent the vomiting reflex.

This mechanism makes it effective for controlling nausea and vomiting related to various medical treatments.

Common side effects of Ondansetron

Not everyone experiences side effects with ondansetron, and many are mild and temporary. However, it is important to be aware of them.

Headache
Constipation
Dizziness
Fatigue
Diarrhea
Feeling of warmth or flushing
Hiccups

If you experience serious or persistent side effects, contact your healthcare provider.

Inform your doctor about any allergies or medical conditions before taking ondansetron.
Avoid drinking alcohol while taking this medication, as it may increase certain side effects.
Be cautious when driving or using machinery until you know how ondansetron affects you.
Do not take ondansetron if you experience severe allergic reactions to similar medications.
Discuss any other medications you are taking with your doctor to avoid potential interactions.

Always consult your healthcare provider for guidance related to your specific health needs.

Frequently Asked Questions

What is ondansetron used for?

Ondansetron is used to prevent nausea and vomiting caused by medical treatments such as chemotherapy, surgery, and radiotherapy.

How does ondansetron work?

Ondansetron works by blocking serotonin receptors that can trigger nausea and vomiting in the brain and gut.

How quickly does ondansetron start working?

Ondansetron typically begins to work within a short period after administration, but the exact time can vary between individuals.

Is ondansetron safe to use during pregnancy?

The safety of ondansetron during pregnancy is not fully established. Consult your doctor for advice specific to your situation.

Can ondansetron interact with other medications?

Yes, ondansetron can interact with other medications. It’s important to inform your doctor about all the medications you are taking.