Ondansetron: Uses, How It Works, Medicines
Ondansetron is a prescription medicine that prevents nausea and vomiting caused by cancer treatment (chemotherapy and radiotherapy) and by surgery. It belongs to a group called 5-HT3 blockers. It can affect the heart's rhythm in some people. It is used only on a doctor's advice.
Also known as: Ondansetron 4 mg, Ondansetron tablet, Ondansetron hydrochloride, Ondansetron IP, Zofran, Ondem, Emeset, Vomikind, Anti-sickness tablet
Pharmacist review in progress. This page is based on the sources listed below and is being checked by our registered pharmacist.
How does Ondansetron work?
Ondansetron blocks serotonin (5-HT3) receptors on nerves in the gut and in the part of the brain that triggers vomiting. With this signal blocked, the urge to vomit is reduced.
How to take Ondansetron
Follow the label or your doctor's advice. Ondansetron is taken by mouth, with or without food, and the number of doses depends on the reason it was prescribed. Your doctor decides the dose and how long you need it.
Side effects of Ondansetron
Most people tolerate ondansetron well. The common side effects are mild, but a few effects need urgent medical help.
Uncommon or mild
- Headache
- Constipation
- Tiredness or weakness
- Diarrhoea
- Drowsiness or feeling cold
Rare but serious: get medical help
- Signs of a severe allergic reaction: swelling of the face, lips or throat, difficulty breathing or a sudden widespread rash. Get medical help immediately
- A fast, slow or irregular heartbeat, chest pain, dizziness or fainting
- Changes or loss of vision
- Agitation, confusion, seeing things that are not there, fever, heavy sweating, muscle stiffness or twitching, or loss of coordination, which can be signs of serotonin syndrome
Who should be careful
Ondansetron can affect the heart's rhythm, and some people need a doctor's check before taking it.
When the label says not to use it
- Allergy to ondansetron or to any ingredient in the tablet
- Treatment with apomorphine, because the combination can cause a sharp drop in blood pressure and loss of consciousness
- Heart rhythm: tell your doctor if you or a family member has long QT syndrome or another heart rhythm problem, heart failure, or a slow heartbeat
- Low potassium or magnesium, for example after vomiting or diarrhoea: these raise the heart rhythm risk
- Liver disease: the medicine stays in the body longer and the dose may need to be limited
- Pregnancy: studies are inconsistent, so tell your doctor if you are pregnant or planning a pregnancy
- Breastfeeding: ask your doctor first
- Orally disintegrating (melt-in-mouth) forms may contain aspartame, which matters for people with phenylketonuria
- Vomiting that is severe, lasts a long time or contains blood needs a doctor's check; ondansetron can hide a problem that needs treatment
Medicines and things that interact with Ondansetron
Ondansetron can interact with several medicines. Tell your doctor or pharmacist about everything you take.
- Apomorphine: must not be combined
- Medicines that also affect heart rhythm, such as some antibiotics, antipsychotics and heart medicines: the risk of a heart rhythm problem rises
- Medicines that raise serotonin, such as SSRI and SNRI antidepressants, MAO inhibitors, tramadol and fentanyl: serotonin syndrome has been reported
- Phenytoin, carbamazepine and rifampicin: they may lower ondansetron levels
If someone takes too much
Taking one extra tablet by mistake is unlikely to be serious, but larger amounts can cause brief vision loss, dizziness, fainting, constipation and an irregular heartbeat. If someone has taken much more than prescribed, call 112 or go to the nearest hospital and take the medicine pack with you.
Regulatory status in India
Approved for sale in India as a prescription medicine. Single-ingredient ondansetron is not mentioned in the CDSCO section 26A banned list text checked for this batch; the reviewer should confirm.
Type of medicine
Ondansetron belongs to this type of medicine.
Medicines that contain Ondansetron
These medicines sold in India contain Ondansetron. They are listed A to Z, not ranked.
- Ondem 4 · 4 mg tablet
What is Ondansetron used for?
Medicines that contain Ondansetron are used for these conditions.
Common questions
What is ondansetron used for?
Ondansetron is a prescription medicine that prevents nausea and vomiting after chemotherapy, radiotherapy or surgery. A doctor may prescribe it for other causes of sickness. It should be taken only as prescribed.
Does ondansetron affect the heart?
It can. Ondansetron may change the heart's rhythm (QT interval), mainly in people with a heart rhythm problem, low potassium or magnesium, or those taking other medicines with the same effect. Tell your doctor about heart problems before taking it.
Can ondansetron cause constipation?
Yes, constipation is one of the most common side effects. Drinking fluids and eating fibre can help. If it is severe or does not go away, tell your doctor or pharmacist.
Is ondansetron the same as domperidone?
No. Ondansetron blocks serotonin signals, while domperidone blocks dopamine and speeds up stomach emptying. They are different medicines for different situations, and both can affect heart rhythm. Do not swap them or combine them without a doctor's advice.
Sources
- Ondansetron tablets: prescribing information. DailyMed, US National Library of Medicine
- Ondansetron. MedlinePlus, US National Library of Medicine
- ATC/DDD Index: A04AA01 ondansetron. WHO Collaborating Centre for Drug Statistics Methodology
- Diarrhoea and vomiting. NHS (UK)
- List of drugs prohibited for manufacture and sale through gazette notifications under section 26A of the Drugs & Cosmetics Act 1940. Central Drugs Standard Control Organisation (CDSCO)