Pharmacology · Inhaled anaesthetics
Halothane !
An old inhaled anaesthetic, now nearly abandoned because of the severe hepatitis it can cause. It triggers malignant hyperthermia.
Updated 2026-11-01
Mechanism of action
Halothane is a volatile halogenated alkane (not an ether, like the modern agents) that enhances inhibitory receptors in the central nervous system and produces anaesthesia. It is more soluble in blood than sevoflurane, so induction and emergence are slower. It is metabolised by the liver more than the other halogenated agents; its trifluoroacetylated metabolites can modify liver proteins and trigger an immune response.
- Inhaled, it dissolves in blood and reaches the brain
- Enhances inhibitory receptors: anaesthesia
- Liver metabolism to trifluoroacetylated compounds
- Modified proteins can provoke immune hepatitis
Pharmacokinetics
- Absorption
- Through the lungs; more soluble in blood than modern agents, with slower induction and emergence.
- Metabolism
- Hepatic, to a greater extent than the other halogenated agents.
- Elimination
- Mostly through the lungs; metabolites through the kidney.
Indications
- Maintenance of general anaesthesia where safer agents are not available
Adverse effects
Common
- Hypotension
- Depressed cardiac contractility
- Respiratory depression
Contraindications
- Confirmed hepatitis or unexplained liver dysfunction (jaundice with fever or eosinophilia) after a halogenated agent
- Susceptibility to malignant hyperthermia
Key interactions
- Suxamethonium
- Higher risk of malignant hyperthermia.
- Non-depolarising blockers
- Enhances the block.
- Repeated halogenated exposures within a short time
- Higher risk of hepatitis.
What is monitored
- ECG, blood pressure and saturation
- End-tidal CO2 and temperature
- Liver tests if fever or jaundice appear after anaesthesia
Administration and safety
- Light-sensitive: stored in amber bottles with thymol as preservative.
- Only with a specific calibrated vaporiser.
- Avoid repeating halothane anaesthesia within a short period.
Nursing care
- Before: ask about previous anaesthetics, fever or jaundice after them, and family malignant hyperthermia.
- In the following days: watch for fever, nausea, jaundice or rash.
- During: heart rhythm and blood pressure.
Pregnancy and breastfeeding
Like the other halogenated agents, it relaxes uterine smooth muscle.
Test yourself
Think of the answer, then tap the question to see it.
Which complication limited the use of halothane?
Halothane hepatitis, a rare but highly lethal fulminant hepatic necrosis, probably immune-mediated.
What mechanism is proposed for halothane hepatitis?
Its trifluoroacetylated metabolites bind liver proteins and trigger an immune response.
Why is induction with halothane slower than with sevoflurane?
It is more soluble in blood: alveolar and brain partial pressures take longer to equalise.
Related drugs
← Back to the class: 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: Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 24 (McGraw Hill, 2023); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 13 (McGraw Hill, 2023); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.