Alfaxalone, also known as alphaxalone or alphaxolone and sold under the brand name Alfaxan and Faxone, is a neuroactive steroid and general anesthetic which is used currently in veterinary practice as an induction agent for anesthesia and as an injectable anesthetic. Though it is more expensive than other induction agents, it often preferred due to the lack of depressive effects on the cardiovascular system. The most common side effect seen in current veterinary practice is respiratory depression when Alfaxan is administered concurrently with other sedative and anesthetic drugs; when premedications are not given, veterinary patients also become agitated and hypersensitive when waking up.

Alfaxalone works as a positive allosteric modulator on GABA_A receptors and, at high concentrations, as a direct agonist of the GABA_A receptor. It is cleared quickly by the liver, giving it a relatively short terminal half-life and preventing it from accumulating in the body, lowering the chance of overdose.

Alfaxalone is used as an induction agent, an injectable anesthetic, and a sedative in animals. While it is commonly used in cats and dogs, it has also been successfully used in rabbits, horses, sheep, pigs, and exotics such as red-eared turtles, axolotl, green iguanas, marmosets, and koi fish. As an induction agent, alfaxalone causes the animal to relax enough to be intubated, which then allows the administration of inhalational anesthesia. Premedication (administering sedative drugs prior to induction) increases the potency of alfaxalone as an induction agent. Alfaxalone can be used instead of gas anesthetics in surgeries that are under 30 minutes, where it is given at a constant rate via IV (constant rate infusion); this is especially useful in procedures such as bronchoscopies or repairing tracheal tears, as there is no endotracheal tube in the way. Once the administration of alfaxalone stops, the animal quickly recovers from anesthesia.

Alfaxalone can be used as a sedative when given intramuscularly (IM), though this requires a larger volume (and not all countries allow alfaxalone to be administered IM).

Despite its use as an anesthetic, alfaxalone itself has no analgesic properties.

Though alfaxalone is not licensed for IM or subcutaneous use in the United States (as both cause longer recoveries with greater agitation and hypersensitivity to stimuli), it is routinely used IM in cats, and is licensed as such in other countries.

Alfaxalone is dissolved in 2-hydroxypropyl-β cyclodextrin. The cyclodextrin is a large, starch-derived molecule with a hydrophobic core where alfaxalone stays, allowing the mixture to be dissolved in water and sold as an aqueous solution. They act as one unit, and only dissociate once in vivo.

Alfaxalone has been used to perform C-sections in pregnant cats; though it crosses the placental barrier and had some effects on the kittens, there is no respiratory depression and no lasting effect. Alfaxalone has also been found to be safe in young puppies and kittens.