Ondansetron

Mechanism of Action 12

  • Ondansetron is a selective 5-HT₃ receptor antagonist that blocks serotonin receptors in the chemoreceptor trigger zone (CTZ), preventing the initiation of the vomiting reflex.

Indications 12

  • Prophylaxis and treatment of postoperative nausea and vomiting (PONV).

Dosage 13

  • Postoperative Nausea and Vomiting (PONV) Prophylaxis:
    • Adults: 4 mg IV over 2-5 minutes at the end of surgery.
    • Children: 0.1 mg/kg IV (up to 4 mg) at the end of surgery.
  • Oral: 8 mg orally, 1 hour before anesthesia or chemotherapy (50% bioavailability).

Complications 12

  • Headache: Common, with a number needed to harm (NNH) of 36.
  • QTc Prolongation: May prolong the QT interval
  • Constipation: NNH of 23.
  • Elevated Liver Enzymes: NNH of 31, though often transient and clinically insignificant.

Pharmacokinetics 2

  • Onset of Action: 30 to 60 minutes after oral or IV administration.
  • Metabolism: Hepatic
  • Elimination Half-life: 3 to 4 hours.
  • Excretion: Primarily through urine as metabolites.

References

  1. Gan, T.J., Belani, K.G., Bergese, S., et al. (2020). Fourth Consensus Guidelines for the Management of Postoperative Nausea and Vomiting. Anesth Analg. ↩ ↩2 ↩3 ↩4

  2. Shafer SL, Rathmell JP, Flood P. Stoelting’s Pharmacology and Physiology in Anesthetic Practice. Fifth edition. Philadelphia: Wolters Kluwer Health, 2015. ↩ ↩2 ↩3 ↩4

  3. Coté CJ, Lerman J, Anderson BJ. A Practice of Anesthesia for Infants and Children. Seventh edition. Philadelphia, PA: Elsevier, 2024. ↩