|Storage and Handling||Store at controlled room temperature -20°C|
Alfaxalone is a neuroactive steroid molecule with properties of a general anesthetic. Alfaxalone is chemically described as 3-α-hydroxy-5-α-pregnane-11, 20-dione, and has a molecular weight 332.5. The primary mechanism for the anesthetic action of alfaxalone is modulation of neuronal cell membrane chloride ion transport, induced by binding of alfaxalone to GABAA (gamma-aminobutyric acid) cell surface receptors.
Alfaxalone Mechanism of action
Alfaxalone produces unconsciousness by acting on the gamma aminobutyric acid subtype A (GABAA) receptors in the central nervous system (CNS). These receptors are ionotropic ligand-gated channels, and GABA is their endogenous ligand. GABA is the main inhibitory neurotransmitter in the CNS. After the receptor is activated, the channel opens and promotes chloride conduction into the cell, causing hyperpolarization of the postsynaptic membrane. At low concentrations, alfaxalone positively modulates chloride current through the chloride channel; but at higher concentrations, it functions as a GABA agonist, in the same way as barbiturates. The end result is profound sedation or induction of anesthesia, depending on the dose and route of administration.
Alfaxalone, also known as alphaxolone or alphaxalone and used under the trade name Alfaxan, is a neuroactive steroid and general anesthetic drug used in dogs and cats. It can be used as an induction agent or for general anesthesia.
Alfaxalone Advantages & Disadvantages
Alfaxalone causes minimal change in cardiac output or blood pressure when clinically relevant doses are administered to healthy patients. Alfaxalone has a high therapeutic index, is short acting, and noncumulative. These characteristics make alfaxalone ideal for use as an induction agent or for providing injectable anesthesia.
Alfaxalone can also be administered intramuscularly, thus it can be used to sedate uncooperative patients. When alfaxalone is used to sedate a patient the dose is 1-3mg/kg IM and it is usually co-administered with an opioid for optimal sedation.
When alfaxalone is used for caesarean sections the puppies are more alert and lively with improved AGPAR scores compared to propofol.
Alfaxalone causes dose dependent respiratory depression, with apnea likely to occur following rapid IV injection. Be prepared to intubate, provide oxygen support, and ventilate when using alfaxalone for either induction or sedation.
Excessive administration of alfaxalone can cause dose dependent cardiovascular depression, with significant decreases in both cardiac output and blood pressure . The dose of alfaxalone should be carefully titrated in patients that have reduced cardiovascular reserves or are hemodynamically unstable.
Alfaxalone does not provide any analgesia, therefore it should be used in conjunction with an appropriate opioid for painful procedures.
When alfaxalone is administered intramuscularly the volume of injection can be large, potentially causing pain on injection. The large volume can also make administration challenging when there is a limited window for injection due to patient temperament. Alfaxalone administration can potentially result in poor recoveries characterized by varying degrees of paddling, vocalization, and/or myoclonus.
Reference Whittem T, Pasloske KS, Heit MV et al. (2008) The pharmacokinetics and pharmacodynamics of alfaxalone in cats after single and multiple intravenous administration of Alfaxan at clinical and supraclinical doses. J Vet Pharmacol Ther 31(6), 571-579.  Ferre PJ, Pasloske K, Whittem T et al. (2006) Plasma pharmacokinetics of alfaxalone in dogs after an intravenous bolus of Alfaxan-CD. Vet Anaesth Analg 33, 229–236.  Muir W, Lerche P, Wiese A et al. (2009) The cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in cats. Vet Anaesth Analg 36, 42-54.  Clarke KW, Trim CM, Hall LW, eds. (2014). “Chapter 15: Anaesthesia of the dog”. Veterinary Anaesthesia (11th ed.). Oxford: W.B. Saunders. pp. 135–153.  Varga M (2014). “Chapter 4: Anaesthesia and Analgesia”. Textbook of Rabbit Medicine (2nd ed.). Butterworth-Heinemann. pp. 178–202.  Nieuwendijk H (March 2011). “Alfaxalone”. Veterinary Anesthesia & Analgesia Support Group. Retrieved July 14, 2017.  Zeltzman P (November 17, 2014). “Why Administering Alfaxalone Requires A Bit of Education”. Veterinary Practice News. Retrieved July 14, 2017.