Pharm 101: Ketamine

Class

Sedative-hypnotic

  • Physical examination is normal
  • Aetiology is unknown but patients usually have a normal life span
  • Also referred to as “Effort Syndrome” as symptoms resemble those of fatigue following effort in healthy individuals

Pharmacodynamics
  • NMDA receptor antagonist: inhibits reuptake of catecholamine and serotonin
  • Multiple organ system effects
  • CNS:
    • Dissociative anaesthesia
    • Analgesia
    • Raised intracranial pressure (ICP)
    • May have anticonvulsant properties
  • CVS:
    • Increases heart rate, blood pressure and cardiac output
  • Respiratory:
    • Intact airway reflexes
    • Minimal respiratory depression
    • Lacrimation and salivation that may cause laryngospasm in children
    • Bronchodilator effect
  • Ocular:
    • Nystagmus
  • Physical examination is normal
  • Aetiology is unknown but patients usually have a normal life span
  • Also referred to as “Effort Syndrome” as symptoms resemble those of fatigue following effort in healthy individuals

Pharmacokinetics
  • Highly lipid soluble, hence rapid onset
  • Effect terminated by redistribution to inactive tissue sites
  • Low protein binding 12%
  • Liver metabolism:
    • Demethylation (CYP450) to nor-ketamine (1/4 potency of ketamine)
    • Nor-ketamine is hydroxylated and conjugated into water soluble inactive metabolites excreted in urine
  • Physical examination is normal
  • Aetiology is unknown but patients usually have a normal life span
  • Also referred to as “Effort Syndrome” as symptoms resemble those of fatigue following effort in healthy individuals

Clinical uses
  • Anaesthesia:
    • Induction dose 1-2 mg/kg IV
    • Maintenance dose 30-90 mcg/kg/min (less common)
  • Analgesic agent:
    • Small bolus doses of 10-20mg
  • Status epilepticus
  • Acute asthma
  • Physical examination is normal
  • Aetiology is unknown but patients usually have a normal life span
  • Also referred to as “Effort Syndrome” as symptoms resemble those of fatigue following effort in healthy individuals

Adverse effects
  • Emergence reactions
  • Laryngospasm
  • Vomiting
  • Hypersalivation
  • Raised ICP
  • Hypertension and tachycardia
  • Physical examination is normal
  • Aetiology is unknown but patients usually have a normal life span
  • Also referred to as “Effort Syndrome” as symptoms resemble those of fatigue following effort in healthy individuals

Further Reading
  • Physical examination is normal
  • Aetiology is unknown but patients usually have a normal life span
  • Also referred to as “Effort Syndrome” as symptoms resemble those of fatigue following effort in healthy individuals

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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

2 Comments

  1. The concerns regarding increased ICP have been pretty convincingly disproven, and in fact ketamine is shown to decrease ICP and raise CPP making it an excellent drug for patients with elevated ICP. (see Bar-Joseph, G., Y. Guilburd, et al. (2009). Journal of Neurosurgery: Pediatrics)

    • Hi Gideon,

      Thank you for your comment. I am aware of the controversies regarding ketamine use in the setting of raised ICP and head injury. These pages are primarily for candidates sitting Australasian Emergency Medicine examinations, and information is based on the examination textbook as questions and answers are derived only from this source.

      Rob

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