Acts as a dopamine antagonist and blocks dopamine (D1 and D2) receptors in the brain

Onset of action: 30-40 minutes PO; 10-20 minutes parenteral; 60 minutes PR
Duration of action: 12 h parenteral and oral-extended release; 3-4 h rectal and oral immediate release
Time to peak:
Plasma ½ half life: 3-5 h PO; 7 h parenteral


  • 5-20 mg q6h PO/IV or 25 mg q6h PR
  • Children more than 10 kg or more than 2 years: 0.4 mg/kg/24h in divided doses tid or qid PO/PR


  • Anticholinergic effects: constipation, dry mouth, blurred vision, urinary retention
  • Extrapyramidal symptoms: pseudoparkinsonism, akathisia (restlessness), dystonias, tardive dyskinesia
  • Sedation
  • Orthostatic hypotension
  • Paradoxical agitation/excitement
  • Rash
  • Photosensitivity


This information is drawn from a number of sources (see below). The reader is encouraged to access these and other relevant literature for more detail. As always, sound clinical judgment should be used in individual clinical cases. In particular, it should be remembered that there may be significant variation in the pharmokinetics of a drug resulting from a number of factors, including the individual patient’s metabolism/disease status and how the medication has been formulated.


  1. Brunton LL, Lazo JS, Parker KL, editors. Goodman and Gilman’s: the pharmacological basis of therapeutics. 11th ed. McGraw-Hill Professional; 2006.
  2. Twycross R, Wilcock A. Palliative care formulary. 3rd ed. Radcliffe Medical Press Ltd; 2008.
  3. Repchinsky C, editor. Compendium of pharmaceuticals and specialties (CPS): the Canadian drug reference for health professionals. 44th ed. Canadian Pharmacists Association; 2009.
  4. Goldman A, Hain R, Liben S. Oxford textbook of palliative care for children. 1st ed. Oxford University Press; 2006.

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