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[Pharmacology](https://durgical.com/en/pharmacology/) · [Inhaled anaesthetics](https://durgical.com/en/pharmacology/classes/inhaled-anaesthetics/)

# Isoflurane

Widely used halogenated inhaled anaesthetic for maintaining general anaesthesia. Pungent, it irritates the airway if used for induction.

Updated 2026-11-01

- Class: [Inhaled anaesthetics](https://durgical.com/en/pharmacology/classes/inhaled-anaesthetics/)
- Target: Several central nervous system ion channels (GABA-A and glycine receptors, potassium channels)
- ATC code: N01AB06
- WHO Model List of Essential Medicines

## Mechanism of action

Isoflurane, a volatile halogenated ether, enhances inhibitory GABA-A and glycine receptors and activates two-pore-domain potassium channels, depressing neuronal activity and producing unconsciousness and immobility. It is a vasodilator: it lowers vascular resistance and blood pressure, and it depresses the ventilatory response to hypoxia and hypercapnia.

- Vaporised and inhaled down to the alveoli
- Enhances inhibitory receptors and potassium channels
- Unconsciousness and immobility
- Concentration-dependent vasodilation and hypotension

## Pharmacokinetics

**Absorption**
Through the lungs; its mild pungency limits the speed of induction.

**Metabolism**
A very small fraction is metabolised in the liver.

**Elimination**
Almost all is exhaled unchanged.

## Indications

- Induction and, above all, maintenance of general anaesthesia

## Adverse effects

### Common

- Hypotension
- Reflex tachycardia
- Respiratory depression
- Cough, laryngospasm and apnoea from airway irritation
- Nausea and vomiting
- Emergence agitation in children

### Serious (rare, important)

- Malignant hyperthermia
- Perioperative hyperkalaemia in patients with myopathies, above all Duchenne
- Hepatitis from sensitisation to halogenated agents
- QT prolongation
- Carbon monoxide with a desiccated CO2 absorbent

## Contraindications

- Known or suspected genetic susceptibility to malignant hyperthermia
- Hypersensitivity to isoflurane or other halogenated agents
- Confirmed hepatitis from a halogenated agent, or unexplained liver dysfunction (jaundice with fever or eosinophilia) after one

## Key interactions

**Non-depolarising neuromuscular blockers**
Enhances and prolongs the block.

**Suxamethonium**
Higher risk of malignant hyperthermia.

**Nitrous oxide and opioids**
Lower the MAC.

## What is monitored

- End-tidal agent concentration
- Blood pressure, ECG and saturation
- End-tidal CO2 and temperature

## Administration and safety

- Only with a vaporiser calibrated for isoflurane.
- Replace a desiccated CO2 absorbent before use: it can produce carbon monoxide.
- Keep dantrolene available where it is used.

## Nursing care

- Before: ask about personal or family malignant hyperthermia, myopathies and previous reactions to halogenated agents.
- In recovery: breathing, saturation, blood pressure and nausea.
- Tell parents the child may wake agitated for a short while.

## Pregnancy and breastfeeding

It relaxes uterine muscle; animal studies show effects on the developing brain with long exposures.

## Memory aid

ISOflurane: «Irritates, Slackens the vessels, Old foe of malignant hyperthermia».

## Test yourself

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

## Why is isoflurane not preferred for mask induction?

Its pungent smell irritates the airway and can cause cough, apnoea and laryngospasm; sevoflurane is better tolerated.

## Which toxic gas can form if isoflurane passes through a dry CO2 absorbent?

Carbon monoxide.

## What effect does isoflurane have on non-depolarising blockers?

It enhances and prolongs the block, so lower doses are needed.

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## Related drugs

- [Sevoflurane](https://durgical.com/en/pharmacology/sevoflurane/)
- [Desflurane](https://durgical.com/en/pharmacology/desflurane/)
- [Halothane](https://durgical.com/en/pharmacology/halothane/)

[← Back to the class: Inhaled anaesthetics](https://durgical.com/en/pharmacology/classes/inhaled-anaesthetics/)

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 - ISOFLURANE, (VOLATILE FOR INHALATION)- isoflurane liquid](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=525a2467-548d-4b10-b181-91b90e99ae1b) (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](https://list.essentialmeds.org/) (World Health Organization, 2025); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=N01AB06) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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