Pharm 101: Ketamine

Class

Sedative-hypnotic


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

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

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

Adverse effects
  • Emergence reactions
  • Laryngospasm
  • Vomiting
  • Hypersalivation
  • Raised ICP
  • Hypertension and tachycardia

Further Reading

Pharm 101 700

Pharmacology 101

Top 200 drugs

MBBS (UWA) CCPU Emergency Medicine Trainee with interests in medical education, ECG interpretation, and the use of point-of-care ultrasound in the undifferentiated patient. Co-author of the LITFL ECG Library | Twitter

2 Comments

  1. Gideon Stitt, PharmD, BCPPS, BCCCP
    Gideon Stitt, PharmD, BCPPS, BCCCP

    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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