Pharm 101: Ondansetron



  • 5-HT3 receptor antagonist with peripheral and central actions
  • Works mainly via blockade of peripheral 5-HT3 receptors on extrinsic vagal and spinal afferent nerves
  • Some effect on central 5-HT3 receptors in chemoreceptor trigger zone (CTZ) and vomiting centre
  • Anti-emetic action is restricted to emesis due to vagal stimulation and chemotherapy. Little effect on other emetic stimuli such as motion sickness
  • Half life 4-9 hours
  • Extensive hepatic metabolism
  • Renal and hepatic excretion (dose reduction is required for hepatic insufficiency)
Clinical uses
  • Prevention of chemotherapy-induced nausea and vomiting
  • Treatment and prevention of post-operative and post-radiation nausea and vomiting
Adverse effects
  • Most common are headaches, dizziness, constipation
  • Prolongation of QT interval
  • Serotonin syndrome if taken with other serotonergic drugs
  • Hepatic failure
  • Caution in patients with prolonged QT, especially in conjunction with other medications that may prolong QT interval
Further Reading

Pharmacology 101

Top 200 drugs

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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