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[Pharmacology](https://durgical.com/en/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

## Key points

- High-alert medicines: only with staff trained in airway management, oxygen, continuous monitoring and resuscitation equipment at hand.
- Propofol lowers blood pressure more than the others; etomidate and ketamine better preserve haemodynamics in the unstable patient.
- Ketamine raises blood pressure and heart rate, dilates the bronchi and keeps airway reflexes; its emergence reactions are reduced with benzodiazepines.
- Etomidate suppresses adrenal cortisol synthesis (it blocks 11-beta-hydroxylation), so it is not given as a prolonged infusion.
- Long propofol infusions in the ICU can cause propofol infusion syndrome: metabolic acidosis, hyperkalaemia, rhabdomyolysis and heart failure.

## Drugs in this class

- [**Propofol** Intravenous anaesthetic with fast onset and fast wake-up, the most used to induce anaesthesia and sedate. It lowers… GABA-A receptor (α1β2γ2)](https://durgical.com/en/pharmacology/propofol/)
- [**Ketamine** Anaesthetic that blocks the NMDA receptor: it gives analgesia and «dissociative anaesthesia», preserves breathing and… NMDA glutamate receptor (GluN1/GluN2)](https://durgical.com/en/pharmacology/ketamine/)
- [**Etomidate** Intravenous anaesthetic that barely changes blood pressure: useful to induce the unstable patient. It transiently… GABA-A receptor (α1β2γ2)](https://durgical.com/en/pharmacology/etomidate/)
- [**Dexmedetomidine** Alpha-2 agonist sedative that leaves the patient calm but rousable, without much respiratory depression. It causes… Alpha-2A adrenergic receptor](https://durgical.com/en/pharmacology/dexmedetomidine/)
- [**Thiopental** Ultra-short-acting barbiturate that was the classic induction agent. It precipitates acute porphyria and damages… GABA-A receptor](https://durgical.com/en/pharmacology/thiopental/)

## 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.

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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: Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 24 (McGraw Hill, 2023); [DailyMed - PROPOFOL injection, emulsion](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=3acf8e6c-827d-11e2-9e96-0800200c9a66) (DailyMed (U.S. National Library of Medicine), 2026); [DailyMed - KETAMINE HYDROCHLORIDE injection, solution, concentrate](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bb912318-2e22-4469-b0a2-774803ee1bb8) (DailyMed (U.S. National Library of Medicine), 2026); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/) (World Health Organization, 2025).

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