Alfaxalone is a neurosteroid general anaesthetic

General anaesthetic

A general anaesthetic is a drug that brings about a reversible loss of consciousness. These drugs are generally administered by an anaesthesia provider to induce or maintain general anaesthesia to facilitate surgery...

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It is one of the constituents of althesin

Althesin

Alfaxolone/alfadolone is a short acting intravenous anaesthetic agent, now withdrawn from the market due to severe drug reactions. It is composed of a mixture of alfaxalone and alfadolone, two neurosteroids.Cremophor EL Alfaxolone/alfadolone (Althesin) is a short acting intravenous anaesthetic...

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It is used in veterinary practice under the tradename Alfaxan.
It is licensed for use in both dogs and cats.

Unlike some of its predecessors alfaxalone is not associated with histamine release and anaphylaxis.

A study 1987 found the primary mechanism for the anaesthetic action of alfaxalone to be modulation of neuronal cell membrane chloride ion transport, induced by binding of alfaxalone to GABA_A cell surface receptors.
A study 1994 found that alfaxalone binds to a different region of this receptor than the benzodiazepine

Benzodiazepine

A benzodiazepine is a psychoactive drug whose core chemical structure is the fusion of a benzene ring and a diazepine ring...

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Alfaxalone is metabolised rapidly in the liver. Alfaxalone has a very short plasma elimination half-life in dogs and cats.