Medically reviewed by Jessica Swirble, PharmD
Last updated on April 18, 2025
Drug Information | Side Effects | Use & Dosage | Request an Online Prescription
Ondansetron is a prescription medication used to treat nausea and vomiting caused by surgery, chemotherapy, and radiation treatment.
Ondansetron is used to treat nausea and vomiting caused by surgery, cancer chemotherapy, and radiation treatment.
Ondansetron does not treat underlying causes of nausea and vomiting but reduces these symptoms.
Ondansetron blocks the action of serotonin, a natural chemical in the body that can cause nausea and vomiting. By blocking serotonin receptors in the brain and gut, ondansetron prevents the transmission of nausea signals.
Ondansetron is available in the following forms:
The dosage and frequency of use depend on the condition being treated, its severity, and how you respond to the medication.
Follow your healthcare provider's instructions regarding dosage and schedule. Do not exceed the prescribed dose or frequency of use without consulting your provider.
You may start feeling better within a few hours of taking ondansetron. It is typically used before, during, and after medical procedures to manage symptoms.
Continue using ondansetron as prescribed, even if you start feeling better. Regular use according to your prescription is crucial for the effective prevention of nausea and vomiting.
While ondansetron is primarily used for preventing nausea and vomiting caused by medical treatments, healthcare providers may prescribe it off-label for other types of nausea and vomiting, such as that associated with gastroenteritis.
Discuss any alternative uses of ondansetron with your healthcare provider.
Ondansetron is available in the following dosage forms:
Ondansetron is a prescription medication. You will need a valid prescription from a licensed healthcare provider to obtain this medication.
The use of ondansetron can lead to various side effects in some individuals.
Common mild side effects of ondansetron use include:
More severe side effects of ondansetron use can include:
If you experience any severe or concerning side effects while taking ondansetron, contact your healthcare provider right away.
Inform your healthcare provider about any existing medical conditions, allergies, or other medications you are taking before starting treatment with ondansetron. This includes prescription drugs, over-the-counter medications, and dietary supplements, as they may interact with ondansetron.
Tell your provider if you are taking these medications or supplements:
You should also mention medical conditions such as:
If you are pregnant, planning to become pregnant, or breastfeeding, discuss the potential risks and benefits of using ondansetron with your healthcare provider.
Take ondansetron exactly as prescribed by your healthcare provider. Do not exceed the recommended dose or length of treatment.
Ondansetron can be taken with or without food. It's important to complete the full course of treatment, especially if it's part of a scheduled regimen around chemotherapy or surgery, to ensure the medication's effectiveness in managing nausea and vomiting.
In case of an ondansetron overdose, seek medical attention immediately. Symptoms of overdose may include severe constipation, vision changes, fainting, or severe dizziness. If you suspect an overdose, contact the poison control helpline at 1-800-222-1222 or call emergency services.
Ondansetron is available in the following forms:
The typical starting dose of ondansetron varies depending on the condition being treated, the severity of symptoms, and individual patient factors. It is crucial to follow your healthcare provider's instructions regarding dosage and administration.
For prevention of nausea and vomiting caused by chemotherapy:
For nausea and vomiting after surgery:
The dosage may be adjusted based on the response and tolerance to the medication. Your healthcare provider will determine the most appropriate dose based on your medical history and your response to the medication.
Ondansetron should be taken as prescribed by your healthcare provider. Do not exceed the recommended dose or duration of treatment without consulting your provider.
If you have any questions about your dosage or need adjustments, contact your healthcare provider for guidance. If you want to talk to a provider right away, consider scheduling an online doctor appointment through a telehealth platform like Sesame.
If you miss a dose of ondansetron, take it as soon as you remember unless it is close to the time for your next scheduled dose. In that case, skip the missed dose and continue your regular dosing schedule. Do not double the dose to make up for a missed one.
Take ondansetron around the same time every day to maintain an even level of medication in your body.
Continue taking ondansetron as prescribed by your healthcare provider, even if you start feeling better. It's important to keep taking the medication as directed to manage your condition effectively.
If you have any concerns or questions about your medication, discuss them with your healthcare provider for medical advice and recommendations.
Store ondansetron according to the instructions provided by your healthcare provider or pharmacist. Keep it at room temperature, away from light and moisture. Ensure the container is tightly closed and out of reach of children.
Do not use expired medication or medications that appear damaged or discolored. If you have any questions about storage, consult your healthcare provider or pharmacist for guidance.