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Ondansetron and QT prolongation — FRCA Primary MCQ

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HardPharmacologyOndansetron and QT prolongationFRCA Primary

A patient with a history of severe postoperative nausea previously responded to ondansetron. She now has QTc 510 ms and hypokalaemia before elective surgery. Which consideration is most important if ondansetron is used?

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Correct answer: A — It causes dopamine receptor blockade and extrapyramidal effects

Ondansetron is a 5-HT3 antagonist that can prolong QT interval, and risk is increased by hypokalaemia and baseline QT prolongation. Extrapyramidal effects are more typical of dopamine antagonists. It does not release histamine or trigger malignant hyperthermia. The pearl is to correct electrolytes and consider alternative antiemetic strategies in marked QT prolongation.

Reference: RCoA Primary FRCA Syllabus 2026; Peck, Hill & Williams Pharmacology for Anaesthesia