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What does it do?

Ondansetron is used to treat and prevent nausea and vomiting.

Before you start

  • Tell your doctor if you have liver, heart or bowel problems.
  • Tell your doctor if you are pregnant, planning to become pregnant, or breastfeeding.
  • Tell your doctor if you have phenylketonuria (PKU). The orodispersible tablets and wafers may contain aspartame (a source of phenylalanine).

How should you take it?

Take ondansetron tablets as directed with a glass of water.
Place ondansetron wafers or ‘orodispersible’ tablets on the tongue. Allow to soften for a few seconds and then swallow.

What if you forget a dose?

Should an occasional dose be missed it need not be taken later.

Can you take other medicines?

Some medicines available without a prescription may react with ondansetron including:

  • some migraine medicines, such as sumatriptan (e.g. Sumagran Active®)

Tell your pharmacist or doctor about all medicines or treatments that you may be taking, including vitamins, herbal products (e.g. St John's wort) or recreational drugs.

What side effects might you notice?

Side EffectsRecommended action

Fast or irregular heartbeat, fainting

Tell your doctor immediately

Headache, dizziness

Drowsiness, tiredness or weakness

Flushing, fever

Tingling or numbness


Tell your doctor if troublesome

If you notice any other effects, discuss them with your doctor or pharmacist.

This leaflet contains important, but not all, information about this medicine.

Prepared by the MyMedicines Committee at Christchurch Hospital, Te Whatu Ora - Waitaha, New Zealand. March 2023

For more general information about this sheet and its contents, see: What does a My Medicines sheet cover?

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About My Medicines

My Medicines Patient Information Leaflets (PILs) contain important, but not all, information about the medicines they describe.

For more information about the sheets, see: What does a My Medicines sheet cover?

My Medicines is developed by a team at Te Whatu Ora – Waitaha. Our team is made up of doctors, pharmacists, and a non-medical person to help us keep to plain language. We also discuss our information with specialist health professionals or groups when needed