Pharm 101: Ondansetron

Class

Anti-emetic


Pharmacodynamics
  • 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

Pharmacokinetics
  • 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

Precautions/contraindications
  • Hepatic failure
  • Caution in patients with prolonged QT, especially in conjunction with other medications that may prolong QT interval

Further Reading

Pharm 101 700

Pharmacology 101

Top 200 drugs

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) 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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