Alfaxalone (AX)

Alfaxalone is a neurosteroid general anaesthetic. It is one of the constituents of althesin. 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 GABAA cell surface receptors. Alfaxalone binds to a different region of this receptor than the benzodiazepines.  Alfaxalone is metabolised rapidly in the liver. Alfaxalone has a very short plasma elimination half-life in dogs and cats. Alfaxalone produced dose-dependent anesthesia, cardiorespiratory depression and unresponsiveness to noxious stimulation in unpremedicated cats. Hypoventilation and apnea were the most common side effects.