Table of Contents
- What is Ondansetron?
- Uses of Ondansetron
- How Ondansetron Works
- Forms and Administration
- Effectiveness
- Side Effects
- Precautions
What is Ondansetron?
Ondansetron is a medication primarily used to prevent nausea and vomiting. It belongs to a class of drugs called serotonin 5-HT3 receptor antagonists[1]. This medication is also known by its brand name Zofran, which is manufactured by GlaxoSmithKline[2].
Uses of Ondansetron
Ondansetron is prescribed for several conditions that cause nausea and vomiting:
- Postoperative Nausea and Vomiting (PONV): This is a common side effect after surgery, especially following procedures like vitrectomy (eye surgery) or thyroidectomy (thyroid gland removal)[1][3].
- Chemotherapy-Induced Nausea and Vomiting: Ondansetron helps cancer patients manage nausea and vomiting caused by chemotherapy treatments[4].
- Nausea and Vomiting in Pregnancy: Although not explicitly mentioned in the trials, Ondansetron is sometimes used to treat severe morning sickness in pregnant women.
- Prevention of Hypotension During Spinal Anesthesia: In some cases, Ondansetron is used to help prevent low blood pressure during spinal anesthesia for cesarean sections[5].
How Ondansetron Works
Ondansetron works by blocking the action of serotonin, a natural substance in the body that can trigger nausea and vomiting. Specifically, it inhibits the Bezold-Jarisch reflex, which is responsible for causing hypotension (low blood pressure) and bradycardia (slow heart rate) in response to certain stimuli[5]. By blocking this reflex, Ondansetron can help prevent nausea, vomiting, and in some cases, low blood pressure.
Forms and Administration
Ondansetron comes in several forms:
- Tablets: Regular tablets that you swallow with water[2].
- Orally Disintegrating Tablets (ODT): These tablets dissolve in your mouth without needing water[4].
- Orally Dissolving Film Strip (ODFS): A thin strip that dissolves on your tongue[4].
- Intravenous (IV) Injection: Given directly into a vein by a healthcare professional[5].
The dosage and form of Ondansetron prescribed will depend on the specific condition being treated and the patient’s individual needs.
Effectiveness
Several studies have shown Ondansetron to be effective in preventing nausea and vomiting:
- In patients undergoing vitrectomy surgery, Ondansetron combined with dexamethasone (another anti-nausea medication) was found to be effective in preventing PONV[1].
- For cesarean sections, Ondansetron has shown promise in reducing the amount of other medications needed to maintain blood pressure during spinal anesthesia[5].
- Studies comparing different forms of Ondansetron (such as orally disintegrating tablets and orally dissolving film strips) have shown them to be equally effective, giving patients more options for taking the medication[4].
Side Effects
While Ondansetron is generally well-tolerated, it can cause some side effects. Common side effects may include:
- Headache
- Constipation
- Dizziness
- Tiredness
More serious side effects are rare but can include allergic reactions or changes in heart rhythm. It’s important to discuss any side effects with your healthcare provider[1].
Precautions
While Ondansetron is a valuable medication for many patients, there are some precautions to consider:
- Drug Interactions: Ondansetron may interact with other medications. For example, one study suggested a potential interaction between Ondansetron and acetaminophen (paracetamol) in post-operative pain management[3].
- Pregnancy and Breastfeeding: While Ondansetron is sometimes used for severe morning sickness, its safety during pregnancy and breastfeeding should be discussed with a healthcare provider.
- Liver Function: Patients with liver problems may need dose adjustments.
Always inform your healthcare provider about all medications you’re taking and any medical conditions you have before starting Ondansetron.


