Alfaxalone for Anesthesia in Dogs and Cats: What You Should Know

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. Although expensive, it has some important advantages. Below I’ll give you information about dosing, advantages, and some disadvantages.

What is Alfaxalone?

Alfaxalone is a neuroactive steroid that is approved for use as an injectable anesthetic agent in dogs and cats. Alfaxalone can be used for sedation, induction of anesthesia, and for total intravenous anesthesia (TIVA). Administration of alfaxalone can provide muscle relaxation, chemical restraint, and/or general anesthesia.

What is the Formulation and Dosing of Alfaxalone?

Alfaxalone is a clear/colorless solution that is formulated at a concentration of 10mg/mL. When alfaxalone is used as an induction agent the dose is 0.5-2.5 mg/kg slow IV to effect.

What are Some Advantages of Using Alfaxalone?

Alfaxalone causes minimal change in cardiac output or blood pressure when clinically relevant doses are administered to healthy patients (Muir et al 2008, Muir et al 2009). Alfaxalone has a high therapeutic index, is short acting, and noncumulative (Ferre et al 2006, Whittem et al 2008). 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 (Doebeli et al 2013).

What are Some Disadvantages of Using Alfaxalone?

Alfaxalone causes dose dependent respiratory depression, with apnea likely to occur following rapid IV injection (Muir et al 2008, Muir et al 2009). 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 (Muir et al 2008, Muir et al 2009). 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.

References

• Doebeli A, Michel E, Bettschart R et al. (2013) Apgar score after induction of anesthesia for canine cesarean section with alfaxalone versus propofol. Therio 80(8), 850-854.
• 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. (2008) Cardiorespiratory and anesthetic effects of clinical and
• supraclinical doses of alfaxalone in dogs. Vet Anaesth Analg 35, 451–462.
• 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.
• 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.