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5-HT3 Receptor Antagonist — Nausea / Vomiting / Gastroenteritis

Ondansetron (Paediatric)

Brand names: Zofran, Ondansetron Orodispersible

Ondansetron (paediatric) is a 5-HT3 receptor antagonist antiemetic used in children to prevent and treat nausea and vomiting due to chemotherapy, radiotherapy and surgery, and is used off-label for vomiting in acute gastroenteritis. This page covers its use in the paediatric population.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It blocks serotonin 5-HT3 receptors in the gut and the chemoreceptor trigger zone, interrupting the emetic reflex.

Prescribing in practice

  • The most important paediatric concern is dose-dependent QT-interval prolongation; it should be used cautiously where there is congenital long-QT syndrome, electrolyte disturbance or concomitant QT-prolonging drugs.
  • Constipation and headache are common, and electrolytes (potassium and magnesium) should be corrected before use in at-risk children.
  • It is available in oral, orodispersible and intravenous forms; doses are weight-based and should be confirmed against a children's formulary.

Monitoring

Monitor for ECG/QT effects in at-risk children, electrolytes, bowel function and antiemetic response.

Counselling the patient

  • The orodispersible tablet dissolves on the tongue and is useful when swallowing is difficult.
  • Report fainting, palpitations or an irregular heartbeat.
  • Constipation is common, so encourage fluids and fibre.

Evidence & guidelines

The MHRA has highlighted the risk of QT prolongation with ondansetron, and its efficacy for paediatric vomiting in gastroenteritis is supported by clinical trial evidence.

Reference: MHRA Drug Safety Update 2013 (Ondansetron QT); PERN Study; Ramsook 2002 (Gastroenteritis RCT); Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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