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Pharmacology · Intravenous anaesthetics

Ketamine !

Anaesthetic that blocks the NMDA receptor: it gives analgesia and «dissociative anaesthesia», preserves breathing and raises blood pressure.

Updated 2026-11-01

  • Class: Intravenous anaesthetics
  • Receptor: NMDA glutamate receptor (GluN1/GluN2)
  • ATC code: N01AX03
  • WHO Model List of Essential Medicines

Also called: Ketamine hydrochloride

The figure shows S-ketamine (esketamine) in the channel pore of the human GluN1–GluN2A NMDA receptor, with glycine and glutamate.

Target in 3D: NMDA glutamate receptor (GluN1/GluN2). PDB structure 7EU7 (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Ketamine, an arylcyclohexylamine related to phencyclidine, is a non-competitive NMDA receptor antagonist: it enters the open channel and blocks the glutamate-activated ion flow. It disconnects thalamocortical from limbic pathways, so the patient seems awake (eyes open, nystagmus) but does not respond or feel pain. It also inhibits catecholamine reuptake, which raises blood pressure, heart rate and cardiac output, and relaxes bronchial muscle.

  1. Enters the open channel of the NMDA receptor
  2. Blocks the current that glutamate activates
  3. Thalamocortical-limbic disconnection: dissociative anaesthesia and analgesia
  4. Inhibits catecholamine reuptake: blood pressure and heart rate rise

Pharmacokinetics

Absorption
Intravenous or intramuscular; onset is somewhat slower by the intramuscular route.
Distribution
Very lipid-soluble: it reaches the brain in seconds and then redistributes.
Metabolism
Hepatic by CYP enzymes (mainly CYP3A4) to norketamine, a less potent active metabolite.
Elimination
Kidney, as metabolites.
Onset and duration
Seconds intravenously; anaesthesia from one dose lasts a few minutes.

Indications

  • Induction and anaesthesia for short procedures, alone or with other drugs
  • Sedation and analgesia for painful procedures, especially in children
  • Induction in patients at risk of hypotension, such as shock Hypovolaemic shock →
  • Induction in patients with bronchospasm or severe asthma Asthma →

Adverse effects

Common

  • Emergence reactions: vivid dreams, hallucinations, confusion
  • Hypertension and tachycardia
  • Nystagmus and double vision
  • Hypersalivation
  • Increased muscle tone and movements
  • Nausea and vomiting

Contraindications

  • Patients in whom a significant rise in blood pressure would be dangerous
  • Hypersensitivity to ketamine

Key interactions

Benzodiazepines, opioids, alcohol and other depressants
Deep sedation and respiratory depression; benzodiazepines reduce emergence reactions.
Theophylline or aminophylline
Lower the seizure threshold.

What is monitored

  • Blood pressure and heart rate
  • Breathing, saturation and airway
  • Mental state on emergence
  • Liver tests with repeated use

Administration and safety

  • Slow intravenous injection: rapid injection raises the risk of apnoea and hypertension.
  • Airway equipment and oxygen available; pharyngeal reflexes are preserved but do not guarantee a protected airway.
  • Controlled medicine because of its abuse potential: records and secure storage.
  • Several strengths of the product exist: check the presentation before drawing up the syringe.

Nursing care

  • Emergence in a quiet setting with dim light, little noise and no unnecessary stimuli.
  • Watch blood pressure, heart rate and saturation until full recovery.
  • Keep suction ready: salivation increases.
  • Ask about recreational ketamine use and urinary symptoms with repeated use.

Pregnancy and breastfeeding

Used for caesarean sections without a clear risk to mother or fetus in the available data; animal studies show developmental effects, so it is kept for when it is needed.

Test yourself

Think of the answer, then tap the question to see it.

Why is ketamine useful to induce a patient in shock?

Its indirect sympathomimetic effect (it inhibits catecholamine reuptake) usually maintains or raises blood pressure and heart rate.

In which patient with cardiovascular disease is ketamine avoided?

In someone for whom a significant rise in blood pressure would be dangerous, and with care when there is a risk of ischaemia, because it raises myocardial oxygen consumption.

Which drug is added to ketamine to reduce emergence reactions?

A benzodiazepine, together with an emergence with few stimuli.

Which receptor does ketamine block?

The NMDA glutamate receptor, as a non-competitive antagonist inside the channel.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - KETAMINE HYDROCHLORIDE injection, solution, concentrate (DailyMed (U.S. National Library of Medicine), 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 24 (McGraw Hill, 2023); eEML - Electronic Essential Medicines List (World Health Organization, 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.