Ondansetron
Ondansetron is an antiemetic of the 5-HT3 receptor antagonist class. It is used to prevent nausea and vomiting, including the nausea and vomiting that can follow an operation. Zofran tablets contain ondansetron and come in 4 mg and 8 mg strengths.
Medicine containing Ondansetron
Key points
- Ondansetron blocks 5-HT3 receptors on vagus nerve terminals and in the chemoreceptor trigger zone of the brain, which inhibits the emetogenic response.
- It starts to act within 30 to 60 minutes, and its effect lasts around 8 to 12 hours.
- It is produced as film-coated tablets and as orodispersible tablets that dissolve on the tongue.
What ondansetron is used for
Ondansetron is given to prevent nausea and vomiting, including after surgery. Film-coated tablets are swallowed with water. The orodispersible form is an option for people who have trouble swallowing tablets, or who cannot keep a tablet down.
How it works
Ondansetron is a potent, highly selective 5-HT3 receptor antagonist. Serotonin acting at 5-HT3 receptors on vagus nerve terminals and in the chemoreceptor trigger zone sets off the vomiting reflex. Blocking those receptors inhibits the emetogenic response to chemotherapy and to surgery.
Forms and brands
Zofran is the brand under which ondansetron appears here, as Zofran tablets in 4 mg and 8 mg. An orodispersible tablet is the other dosage form. Pharmacy partners in India ship orders to Malaysia in discreet packaging.
Safety
Ondansetron must not be used by anyone with a hypersensitivity to it, or together with apomorphine. It is avoided in people with congenital long QT syndrome, and an ECG is advised where there are electrolyte abnormalities, cardiac failure, arrhythmias, or other QT-prolonging drugs. Use it with caution in hepatic impairment. Severe constipation needs monitoring, and the medicine may mask the symptoms of bowel obstruction. Serotonin syndrome has been reported with 5-HT3 antagonists, particularly when serotonergic drugs are taken at the same time.
Headache, flushing and constipation are common. Raised liver enzymes, dizziness and abdominal discomfort also occur. QT prolongation, arrhythmia and anaphylaxis are serious and require immediate medical attention.
Ondansetron is not routinely recommended in pregnancy, especially during the first trimester. Formula feeding is recommended if treatment is needed while breastfeeding. Use in children requires caution, with specialist paediatric dosing guidance.
What the sources say
- Prevention of postoperative nausea and vomiting is among the labelled uses (DailyMed).
- The label says to avoid ondansetron in patients with congenital long QT syndrome (DailyMed).
- Electrocardiogram monitoring is directed where there are electrolyte abnormalities, cardiac failure or arrhythmias, or other QT-prolonging drugs (DailyMed).
- Concomitant use of apomorphine is a contraindication (DailyMed).
Further reading
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