Title: Alfaxalone
CAS Registry Number: 23930-19-0
CAS Name: (3a,5a)-3-Hydroxypregnane-11,20-dione
Additional Names: alphaxalone
Manufacturers' Codes: GR-2/234
Molecular Formula: C21H32O3
Molecular Weight: 332.48
Percent Composition: C 75.86%, H 9.70%, O 14.44%
Literature References: Prepn: Nagata et al., Helv. Chim. Acta 42, 1399 (1959); Browne, Kirk, J. Chem. Soc. C 1969, 1653; Davis et al., DE 2030402; ZA 7003861 (both 1971 to Glaxo), C.A. 75, 20793n, 64114w (1971). Mass spectral data: Ende, Spiteller, Monatsh. Chem. 102, 929 (1971). Review of pharmacology and clinical efficacy of mixture with alfadolone acetate, q.v.: Postgrad. Med. J. 48, Suppl. 2, 1-139 (1972). See also Child et al.; Campbell et al.; Br. J. Anaesth. 43, 2-24 (1971); Lancet 1, 888 (1972). Pharmacology and toxicity data: M. I. Al-Khawashki et al., J. Egypt. Med. Assoc. 62, 191 (1979).
Properties: Colorless prisms from ether, mp 172-174°. [a]D26 +113.4° (c = 1.2 in chloroform). LD50 i.v. in mice: 43 mg/kg (Al-Khawashki).
Melting point: mp 172-174°
Optical Rotation: [a]D26 +113.4° (c = 1.2 in chloroform).
Toxicity data: LD50 i.v. in mice: 43 mg/kg (Al-Khawashki)
Derivative Type: Mixture with alfadolone acetate
CAS Registry Number: 8067-82-1
Additional Names: Alphadione; alfadione
Manufacturers' Codes: CT-1341
Trademarks: Alfatésin (Glaxo); Althesin (Glaxo); Saffan (Mallinckrodt)
Properties: LD50 in mice (mg/kg): 140 i.p., 47 i.v. (Al-Khawashki).
Toxicity data: LD50 in mice (mg/kg): 140 i.p., 47 i.v. (Al-Khawashki)
Therap-Cat: Combination with alfadolone acetate as anesthetic (intravenous).
Therap-Cat-Vet: Combination with alfadolone acetate as anesthetic (intravenous).
Keywords: Anesthetic (Intravenous).
Alfentanil Alfimeprase Alfuzosin Algestone Algestone Acetophenide

Systematic (IUPAC) name
Clinical data
AHFS/ International Drug Names
Legal status  ?
Pharmacokinetic data
Bioavailability The alfaxalone molecule is solubilised in the Alfaxan formulation using 2α- hydroxypropyl β cyclodextrin. Cyclodextrins are complex polysaccharides derived from starch that supply a hydrophobic centre for lipophilic drugs like alfaxalone.
CAS number 23930-19-0 N
ATC code N01AX05
PubChem CID 104845
ChemSpider 94637 YesY
KEGG D07282 YesY
Chemical data
Formula C21H32O3 
Mol. mass 332.477 g/mol
 N (what is this?)  (verify)

Alfaxalone (INN, also known as alphaxalone or alphaxolone) is a neurosteroid general anaesthetic.

It is one of the constituents of althesin.

It is used in veterinary practice under the tradename Alfaxan. [1]

It is licensed for use in both dogs and cats.[citation needed]

Unlike some of its predecessors alfaxalone is not associated with histamine release and anaphylaxis.[citation needed]

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. [2]

A 1994 study found that alfaxalone binds to a different region of this receptor than the benzodiazepines. [3]

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