What is Zofran (ondansetron)?
Zofran is a medication primarily used to prevent nausea and vomiting caused by chemotherapy, radiation therapy, and surgery. It belongs to a class of drugs known as antiemetics. Zofran works by blocking the action of serotonin, a chemical in the body that triggers vomiting. It is available in tablet form, as well as an oral disintegrating tablet and liquid solution. The medication is typically taken before undergoing treatment or surgery, and its effects can last for several hours. Common side effects may include headache, constipation, and dizziness. Zofran is prescribed by healthcare professionals and should be used as directed.

Prescription Required.
Product of Canada.
Shipped from Canada.
Prescription Required. | Product of Canada. | Shipped from Canada. |
What is Zofran (ondansetron)?
Zofran is a medication prescribed for the prevention of nausea and vomiting as a result of chemotherapy treatment, radiation treatment, and surgery.
Zofran belongs to the drug class, antiemetics. These types of medications work by blocking messages your body sends to the brain about nausea. Blocking these signals reduces and can prevent nausea that leads to vomiting.
What are the Indications for Zofran?
Zofran is indicated for the prevention of nausea associated with cancer chemotherapy that have a tendency to highly or moderately induce nausea (emetogenic) leading to vomiting. Zofran may also be used to prevent nausea as a result of radiotherapy for those undergoing radiation treatment as well as for postoperative recovery from surgery.
Zofran is not recommended if you are allergic to Zofran or any ingredients in Zofran.
How is Zofran used?
Storage
Zofran tablets should be stored at room temperature between 36°F and 86°F (2°C – 30°C). Keep Zofran away from light in a tight-lidded container that does not allow light to pass.
Keep out of reach of children.
Instruction
Take Zofran as directed by your doctor depending on your diagnosis, with or without food.
ZOFRAN ODT Orally Disintegrating Tablets
Peel the foil backing and carefully remove the tablet as it can crumble easily. Place the tablet on your tongue and allow it to dissolve with your saliva. No water is needed.
If you miss a dose, take it as soon as you remember. If it is past the day you should have taken Zofran, skip the missed dose, and take your next dose at your next scheduled time.
Dosage
Zofran is available in three forms: tablet, orally disintegrating tablet, and oral solution.
- Zofran tablets are available in the following strengths: 4 mg and 8 mg.
- Zofran orally disintegrating tablets are available in the following forms: 4 mg and 8 mg.
- Zofran oral solution is available as 4 mg/5ml in a 50-mL bottle.
The recommended dosage is dependent on your diagnosis. If you are taking Zofran for:
Highly Emetogenic Cancer Chemotherapy
The recommended dose is 24 mg to be taken 30 minutes before chemotherapy treatment that may highly induce nausea.
Moderately Emetogenic Cancer Chemotherapy
18+ years of age: The recommended dose is 8 mg to be taken 30 minutes before chemotherapy treatment followed by a second dose 8 hours after the initial dose. Then take 8 mg two times a day, 12 hours apart, for 1-2 days after the end of chemotherapy.
12 – 17 years of age: The recommended dose is 8 mg to be taken 30 minutes before chemotherapy treatment. Take a second dose 4 hours later followed by a third dose 8 hours after the initial dose. Then take 8 mg three times daily for 1-2 days after the end of chemotherapy.
4 – 11 years of age: The recommended dose is 4 mg to be taken 30 minutes before chemotherapy treatment. Take a second dose 4 hours later followed by a third dose 8 hours after the initial dose. Then take 4 mg three times daily for 1-2 days after the end of chemotherapy.
Radiotherapy
Total body radiation therapy: The recommended dose is 8 mg to be taken 1-2 hours before therapy.
Single high-dose fraction radiotherapy: The recommended dose is 8 mg to be taken 1-2 hours before therapy followed by a 8 mg dose every 8 hours after the initial dose for 1-2 days after the end of radiotherapy.
Daily fractionated radiotherapy: The recommended dose is 8 mg to be taken 1-2 hours before therapy followed by a 8 mg dose every 8 hours after the initial dose for each day of therapy.
Postoperative Surgery
The recommended dose is 16 mg to be taken 1 hour before the start of anesthesia.
Do not change your dosage and take more than what is prescribed without consulting with your doctor. If you took more than prescribed, contact your doctor or seek emergency medical care right away.
Side Effects
It’s important to understand that although Zofran is FDA-approved, it comes with side effects that may or may not affect you.
Before starting Zofran, you should discuss possible side effects with your doctor or pharmacist.
Common Side Effects
Not all side effects require medical attention. As your body adjusts to Zofran, side effects may go away.
Tell your doctor if you experience the following symptoms, and they become severe or do not go away on their own:
- Drowsiness or feeling tired
- Headache
- Diarrhea
- constipation
Serious Side Effects
Severe adverse reactions while taking Zofran can occur. Seek emergency medical care or call 911 if you experience any of the following symptoms:
- Severe allergic reaction: severe rash or itching, swelling in the face, lips, tongue, or throat, rapid heartbeat, fainting or dizziness, or problems breathing or swallowing.
- Fast or pounding heartbeats
- Jaundice (yellowing of the eyes)
- Blurred vision or vision loss
- Severe stomach pain, bloating, or constipation
- Headache with chest pain and fast or pounding heartbeats
The information above does not list all possible side effects. Contact your doctor or pharmacist if you experience any side effects not listed. You or your doctor may report side effects to the FDA by calling 1-800-FDA-1088.
Warnings & Precautions
Before taking Zofran, tell your doctor or pharmacist:
- If you are allergic to any medications such as Zofran
- If you have congenital long QT syndrome
- If you are pregnant or expect to become pregnant or conceive
- If you are breastfeeding or plan to breastfeed
Hypersensitivity Reactions
There have been reports of hypersensitivity reactions when taking Zofran from patients who had hypersensitivity with similar medications. Reported hypersensitivity reactions include anaphylaxis, cardiopulmonary arrest, and bronchospasm. If you experience a hypersensitivity reaction, discontinue use and contact your doctor right away.
Abnormal Heart Rhythm (QT Prolongation)
Taking Zofran may cause abnormal heart rhythm where there is a longer than normal pause between heart beats. Do not take Zofran if you have congenital long QT syndrome. Contact your doctor right away if you experience any of these symptoms or these symptoms have increased.
Serotonin Syndrome
Taking Zofran may result in a condition known as serotonin syndrome. Symptoms of serotonin syndrome include agitation, hallucinations and delirium, autonomic instability such as increased heart rate and blood pressure, dizziness, excessive sweating, flushing, and hyperthermia.
Other effects that may result from taking zofran are neuromuscular symptoms and seizures, which can be accompanied by gastrointestinal problems like vomiting and diarrhea. Contact your doctor right away if you experience any symptoms.
Phenylketonuria (PKU)
Zofran ODT contains phenylalanine which is a component of aspartame. Taking Zofran ODT may impact patients with phenylketonuria. Consult with your doctor before taking Zofran as there are other formulations such as the non-dissolving tablet and solution that may be a safer option.
Interactions & Contraindications
Before taking Zofran, tell your doctor or pharmacist if you take any medications, herbal supplements, or vitamins.
Apomorphine
Taking apomorphine with Zofran may result in hypotension and fainting or a loss in consciousness. Taking both medications can also increase the risk for QT prolongation. Apomorphine should be avoided when taking Zofran unless otherwise directed by your doctor.
Dronedarone
Taking dronedarone with Zofran may significantly increase the potency of Zofran. This can increase the risk for QT prolongation. Dronedarone should be avoided while taking Zofran unless otherwise directed by your doctor.
Lefamulin
Taking lefamulin with Zofran may significantly increase the potency of Zofran. Zofran is metabolized by hepatic enzymes (CYP3A4, CYP2D6, CYP1A2). Taking lefamulin with CYP3A4 medications can increase the risk for irregular heart rhythms. Lefamulin should be avoided while taking Zofran unless otherwise directed by your doctor.
Posaconazole
Taking posaconazole with Zofran may significantly increase the potency of Zofran. Posaconazole should be avoided while taking Zofran unless otherwise directed by your doctor.