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quetiapine

quetiapine

Introduction

  • quetiapine is an atypical benzothiazepine antipsychotic agent introduced in the late 1990's.
  • it is an antagonist at multiple neurotransmitter receptors in the brain.
  • it has been proposed that it's antipsychotic activity is mediated through a combination of dopamine type 2 (D2) and serotonin type 2 (5-HT2) antagonism
  • it also has a high affinity for alpha-adrenergic and histamine receptors but low affinity for muscarinic receptors

P/K

  • well absorbed from the gastrointestinal tract and reaches peak plasma levels within 2 h after oral administration
  • Vd 8-10 L/kg
  • 83% bound to plasma proteins
  • extensively metabolized by the liver (including via CYP3A4 and CYP2D6) to over 20 metabolites, with only 5% of the drug being excreted unchanged

Dose

  • starting dose in adults 25mg bd then titrate every 2 days to a target dose of 75-150mg bd within a week

Overdose

  • appears to have greater safety in overdose than traditional antipsychotic agents
  • lethality has occurred with doses above 13g

clinical toxicity

  • usually are evident within 4 hours and may last 72 hours
  • most likely to display toxicity at doses above 3g in adults and over 100mg in children
  • sinus tachycardia
  • 1st degree heart block
  • orthostatic hypotension
  • mild-mod anticholinergic effects
  • children may develop extra-pyramidal symptoms up to 3 days later
  • dose-related decreased conscious state and if coma occurs it usually lasts 24-48hrs

Mx

  • ABC's as per usual with cardiac monitoring and may require mechanical restraints
  • if reduced GCS then consider early intubation and consider charcoal once airway protected
  • Mx of seizures:
    • excluding arrhythmia as a cause
    • titrated benzodiazepines
  • Mx of hypotension
    • IV crystalloid as per shock (eg. 10-20mL/kg)
    • consider inotropes
      • WARNING: adrenaline is C/I due to possible paradoxical hypotension due to beta 2 adrenergic vasodilatation
      • noradrenaline appears to be the preferred agent
  • check for urinary retention
quetiapine.txt · Last modified: 2020/09/08 21:42 by gary1