Antiemetic drugs can be classified by their mechanism of action:

  • Serotonin antagonists
    • Ondansetron
  • Corticosteroids
    • Dexamethasone
      Has additional effects on postsurgical pain and fatigue.
  • Dopamine antagonists
    • Phenothiazines
      • Chlorpromazine
      • Prochlorperazine
    • Butyrophenones
      • Droperidol
    • Benzamides
      • Metoclopramide
  • Anticholinergics
    • Hyoscine
    • Atropine
  • Antihistamines
    • Cyclizine
  • NK1 antagonists
    • Aprepitant
  • Others
    • Benzodiazepines
    • Cannabinoids
    • Propofol

Comparison of Antiemetic Drugs

Property Ondansetron Droperidol Metoclopramide Cyclizine
Class Serotonin antagonist Benzamide dopamine antagonist Dopamine antagonist Piperazine derivative/H1 antagonist
Uses Nausea. Ineffective for vomiting due to motion sickness or dopamine agonism Antiemetic, sedation, behavioural control Prokinetic, antiemetic Antiemetic (including motion sickness and radiation sickness)
Presentation Tablet, wafer, clear solution for injection at Clear solution in brown glass, incompatible with thiopentone and methohexital Clear solution in plastic 50mg tablets or light-sensitive solution
Route of Administration PO/SL/IV IV IV/PO PO/IV/IM
Dosing 4-8mg TDS
Give on induction for PONV
Give at end of surgery for PONV
25-50mg IV (note 10mg has no antiemetic properties up to 150mg per day
Absorption PO bioavailability 60% PO bioavailability 30-90% PO bioavailability 80%
Distribution 75% protein bound 90% protein bound, VD Minimal protein binding, VD
Metabolism Hepatic to inactive metabolites. Dose reduction in hepatic impairment. t1/2 3/24. Extensive hepatic metabolism Hepatic metabolism Hepatic to inactive metabolites
Elimination Renal elimination of inactive metabolites Renal and hepatic of drug and metabolites Renal of 20% unchanged drug and remainder as metabolites Renal of metabolites
Mechanism of Action Central and peripheral antagonism of 5-HT3 receptors, reducing input to the vomiting centre Central D2 blockade and post-synaptic GABA antagonism Antiemetic activity via central D2 antagonism, prokinetic activity via muscarinic agonism, peripheral D2 antagonism Competitive H1 antagonist and anticholinergic at M1, M2, M3 receptors
CVS Bradycardia with rapid IV administration, QT prolongation QT prolongation, hypotension secondary to α antagonism ↑/↓ HR, ↑/↓ BP HR and ↓ BP due to α antagonism
CNS Headache Sedation (neurolepsis), extrapyramidal symptoms in ~1% Extrapyramidal symptoms, neuroleptic malignant syndrome Sedation
GIT Constipation Antiemetic Antiemetic, prokinetic Increased LoS tone
Endocrine Hyperprolactinaemia


  1. Peck TE, Hill SA. Pharmacology for Anaesthesia and Intensive Care. 4th Ed. Cambridge University Press. 2014.
  2. Sébastien Pierre, MD, Rachel Whelan. Nausea and Vomiting After Surgery. Contin Educ Anaesth Crit Care Pain 2013; 13 (1): 28-32. doi: 10.1093/bjaceaccp/mks046
  3. Smith S, Scarth E, Sasada M. Drugs in Anaesthesia and Intensive Care. 4th Ed. Oxford University Press. 2011.
Last updated 2017-08-01

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