Pharmacology · Class
Intravenous anaesthetics !
Drugs that, injected into a vein, cause unconsciousness within seconds. They start general anaesthesia and sedate in the ICU and for procedures.
Updated 2026-11-01
What they are
Fast-acting sedative-hypnotics used to induce and, for some, maintain general anaesthesia or sedation: propofol, etomidate and thiopental (hypnotics acting on the GABA-A receptor), ketamine (an NMDA antagonist, «dissociative» anaesthesia) and dexmedetomidine (an alpha-2 agonist, sedation without major respiratory depression).
Mechanism of action
They are highly lipid-soluble: they reach the brain in one circulation time and the patient loses consciousness within seconds. The effect of a single dose ends mainly by redistribution from the brain to muscle and fat, not by metabolism. Propofol, etomidate and barbiturates enhance the chloride current of the GABA-A receptor; ketamine blocks the channel of the NMDA glutamate receptor; dexmedetomidine stimulates alpha-2 receptors in the locus coeruleus.
Target: GABA-A receptor, NMDA receptor, alpha-2A adrenergic receptor
Drugs in this class
- PropofolIntravenous anaesthetic with fast onset and fast wake-up, the most used to induce anaesthesia and sedate. It lowers…GABA-A receptor (α1β2γ2)
- KetamineAnaesthetic that blocks the NMDA receptor: it gives analgesia and «dissociative anaesthesia», preserves breathing and…NMDA glutamate receptor (GluN1/GluN2)
- EtomidateIntravenous anaesthetic that barely changes blood pressure: useful to induce the unstable patient. It transiently…GABA-A receptor (α1β2γ2)
- DexmedetomidineAlpha-2 agonist sedative that leaves the patient calm but rousable, without much respiratory depression. It causes…Alpha-2A adrenergic receptor
- ThiopentalUltra-short-acting barbiturate that was the classic induction agent. It precipitates acute porphyria and damages…GABA-A receptor
Others in the class
- Midazolam
- Remimazolam
- Methohexital
Test yourself
Think of the answer, then tap the question to see it.
What ends the effect of a single dose of propofol or thiopental?
Mainly redistribution of the drug from the brain to muscle and fat; metabolism matters more after long infusions.
Which intravenous anaesthetic raises blood pressure and dilates the bronchi?
Ketamine, through its indirect sympathomimetic effect (it inhibits catecholamine reuptake).
Why is etomidate not used as a continuous infusion?
It blocks adrenal 11-beta-hydroxylation and suppresses cortisol and aldosterone production.
On which receptor do propofol, etomidate and barbiturates act?
On the GABA-A receptor: they increase chloride entry and hyperpolarise neurons.
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 24 (McGraw Hill, 2023); DailyMed - PROPOFOL injection, emulsion (DailyMed (U.S. National Library of Medicine), 2026); DailyMed - KETAMINE HYDROCHLORIDE injection, solution, concentrate (DailyMed (U.S. National Library of Medicine), 2026); eEML - Electronic Essential Medicines List (World Health Organization, 2025).
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Representative model, for educational purposes only.