Pharmacology · Class
Inhaled anaesthetics !
Gases and volatile liquids breathed in to maintain general anaesthesia. Blood carries them to the brain and the lungs remove them.
Updated 2026-11-01
What they are
Volatile halogenated agents (sevoflurane, isoflurane, desflurane, halothane), given through a calibrated vaporiser, and the gas nitrous oxide. They are used mainly to maintain anaesthesia; sevoflurane, which does not irritate the airway, is also used for mask induction in children.
Mechanism of action
They act on several ion channels at once: halogenated agents enhance GABA-A and glycine receptors and open two-pore-domain potassium channels, while nitrous oxide mainly blocks the NMDA receptor. Potency is expressed as MAC (the minimum alveolar concentration that keeps half of patients from moving at incision). The less soluble the agent is in blood, the faster induction and emergence are.
Target: GABA-A and glycine receptors, two-pore-domain potassium channels, NMDA receptor
Drugs in this class
- SevofluraneInhaled anaesthetic with a mild smell and fast effect, ideal for putting children to sleep by mask. It can trigger…Several central nervous system ion channels (GABA-A and glycine receptors, potassium channels)
- IsofluraneWidely used halogenated inhaled anaesthetic for maintaining general anaesthesia. Pungent, it irritates the airway if…Several central nervous system ion channels (GABA-A and glycine receptors, potassium channels)
- Nitrous oxideWeak anaesthetic gas but a good analgesic, combined with oxygen and other anaesthetics. It expands air-filled spaces…NMDA glutamate receptor (and two-pore-domain potassium channels)
- HalothaneAn old inhaled anaesthetic, now nearly abandoned because of the severe hepatitis it can cause. It triggers malignant…Several central nervous system ion channels (GABA-A receptors, potassium channels)
- DesfluraneThe inhaled anaesthetic least soluble in blood: the fastest emergence. It strongly irritates the airway and is not…Several central nervous system ion channels (GABA-A receptors, potassium channels)
Others in the class
- Enflurane
- Xenon
Test yourself
Think of the answer, then tap the question to see it.
What does MAC mean in inhaled anaesthesia?
The minimum alveolar concentration that prevents movement at incision in half of patients; the lower the MAC, the more potent the agent.
Why is induction faster with an agent that is poorly soluble in blood?
Little of it has to dissolve in the blood before the alveolar and brain partial pressures equalise, so they rise quickly.
What is the specific drug for malignant hyperthermia?
Intravenous dantrolene, which curbs calcium release through the skeletal muscle ryanodine receptor.
Why is sevoflurane preferred for mask induction in children?
It is not irritating or pungent to the airway, and its low blood solubility gives a fast induction.
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 - SEVOFLURANE liquid (DailyMed (U.S. National Library of Medicine), 2026); Malignant hyperthermia: MedlinePlus Genetics (MedlinePlus (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.