Alfaxalone

Alfaxalone (INN, JAN), also known as alphaxalone or alphaxolone (BAN), is a neuroactive steroid and general anaesthetic. It is used in veterinary practice under the trade name Alfaxan, and is licensed for use in both dogs and cats. Along with alfadolone, it is also one of the constituents of anesthetic drug mixture althesin.

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 1994 study found that alfaxalone binds to a different region of this receptor than the benzodiazepines. . These benzodiazepine-insensitive GABA_A receptors are located extrasynaptically and are responsible for tonic inhibition. The occurrence of tonic GABA_A inhibition coincides with the expression of relatively rare receptor subunits, particularly the α4, α6, and δ subunits, and as a general rule-of-thumb, δ subunit-containing receptors are extrasynaptic.