Ondansetron

Ondansetron is a 5-HT3 receptor antagonist. The label we reviewed is for orally disintegrating tablets, which dissolve on the tongue.

The label says it is used to prevent nausea and vomiting. This covers chemotherapy that is highly or moderately likely to cause vomiting, radiotherapy, and surgery.

It is for prevention. The label does not describe it as a treatment for everyday stomach upset.

• Highly emetogenic cancer chemotherapy, including high-dose cisplatin
• Moderately emetogenic cancer chemotherapy
• Radiotherapy to the whole body or abdomen
• Postoperative nausea and vomiting

The label says ondansetron blocks serotonin 5-HT3 receptors. These sit on vagal nerve endings and in the brain's vomiting trigger zone.

Chemotherapy appears to release serotonin from the gut, which can start the vomiting reflex. The label says it is not certain whether ondansetron acts in the brain, the gut or both.

It is not a dopamine blocker.

This section describes the orally disintegrating tablet label for adults. Indian tablets, syrups and injections can differ, and your prescriber's instructions come first.

For highly emetogenic chemotherapy, the US label says a single 24 mg dose 30 minutes before treatment. For moderately emetogenic chemotherapy it says 8 mg before treatment, 8 mg after 8 hours, then 8 mg twice daily for 1 to 2 days.

For radiotherapy the label gives 8 mg 1 to 2 hours before treatment, with more doses for abdominal radiotherapy. For surgery it says 16 mg one hour before anesthesia.

In severe liver impairment the label says the total daily dose should not exceed 8 mg.

The label says to peel back the foil with dry hands rather than push the tablet through. Place it on the tongue, where it dissolves, and swallow with saliva. No water is needed.

• Dosing depends on the treatment it is given with
• Severe liver impairment: no more than 8 mg per day on the label
• Orally disintegrating tablets dissolve on the tongue

The label says not to use it if you are allergic to ondansetron, or if you take apomorphine because of a risk of sharp blood pressure drops.

People with congenital long QT syndrome should avoid it. ECG checks are advised for low potassium or magnesium, heart failure, slow heartbeat, or other QT-prolonging medicines.

The orally disintegrating tablets contain phenylalanine, which matters in phenylketonuria.

Liver: in severe impairment, do not exceed 8 mg a day. Older adults: the label says no dose change is needed.

Pregnancy: studies show inconsistent findings and cannot settle the risk. One study linked first-trimester oral use to oral clefts, which other studies did not confirm. Talk to your doctor.

Children: oral use is established from age 4 for moderately emetogenic chemotherapy only.

• Allergy to ondansetron or apomorphine use: do not use
• Congenital long QT syndrome: avoid
• Phenylketonuria: tablets contain phenylalanine
• Severe liver impairment: lower daily maximum

• Apomorphine (contraindicated)
• SSRIs, SNRIs, MAO inhibitors, mirtazapine, fentanyl, lithium, tramadol
• QT-prolonging medicines
• Phenytoin, carbamazepine, rifampin
• Serotonergic medicines such as SSRIs, SNRIs, MAO inhibitors, mirtazapine, fentanyl, lithium and tramadol raise the risk of serotonin syndrome.
• Apomorphine must not be used with it.
• Medicines that prolong the QT interval can add to the heart rhythm risk.
• Strong enzyme inducers such as phenytoin, carbamazepine and rifampin lower ondansetron levels, though the label says no dose change is needed.
• With tramadol, the label says ondansetron may increase the pain medicine needed, so pain control should be checked.

No match in this label text. Ask your pharmacist about any medicine you take.

The label says there is no specific antidote, and care is supportive.

Reported effects include brief blindness with severe constipation, low blood pressure with faintness, and a brief heart block.

In young children, a large accidental overdose has caused serotonin syndrome. Seek medical help right away after an overdose.

For these tablets the label says to store at 20 to 25 degrees C in a tight, light-resistant container.

Leave the tablet in its blister until use. Other forms may have different storage rules, so follow your pack label.

We did not find ondansetron in the Schedule H, H1 or X rows of the Drugs Rules lists we checked. This does not say how a particular pack is sold, so check the pack.

The National List of Essential Medicines 2022 includes ondansetron as a 2 mg per 5 mL oral liquid and a 2 mg per mL injection (pages 85 and 94). Tablets were not found on that list.

NPPA has ceiling prices for ondansetron. The March 2026 list is shown below.

Banned combinations: the list we checked has 2 mentions of ondansetron. Use the checker for your exact combination.

NPPA ceiling prices set the most a seller can charge per unit before local taxes. Check the pack and the seller.

Jan Aushadhi lists ondansetron tablets, an oral solution, an injection, and orally disintegrating tablets and strips. We have not shown a brand price here.

• Ondansetron Tablets IP 4 mg (pack 10's)
• Ondansetron Oral Solution IP 2 mg per 5 mL (30 mL)
• Ondansetron Orally disintegrating Tablets IP 8 mg (pack 10's)
• Ondansetron 4 mg and 8 mg Oral Disintegrating Strips (12's)