Kathryn A. Tuxbury, MS, DVM
Alfaxalone (Alfaxan®) is a synthetic neuroactive steroid, progesterone analog, which binds receptors of the inhibitory neurotransmitter gamma-aminobutyric acid in the central nervous system to induce muscle relaxation, sedation and anesthesia. The drug is FDA approved for intravenous use in dogs and cats and has been studied in a variety of species including birds, reptiles, amphibians, invertebrates, and freshwater fish.1-7 The effects of alfaxalone administered intramuscularly in two marine fish species, permits (Trachinotus falcatus) and schoolmaster snappers (Lutjanus apodus), were studied to determine if intramuscular (IM) alfaxalone will be a useful option for in-tank immobilization procedures of large marine teleost species, thereby facilitating examination, transport and other procedures. Alfaxalone was administered IM to permits at 5 mg/kg (n=8), 7 mg/kg (n=1) and 10 mg/kg (n=2) doses and to schoolmasters at a 5 mg/kg dose (n=4). Response to stimuli and opercular rates were measured every 5 min. The majority of permits and schoolmasters experienced mild, smooth sedation at the 5 mg/kg dose. All permits experienced prolonged excitement phases and duration of effect at the 7 and 10 mg/kg doses. Thus, these doses are not recommended in permits and similar species.
1. Bailey KM, Minter LJ, Lewbart GA, Harms CA, Griffith EH, Posner LP. Alfaxalone as an intramuscular injectable anesthetic in koi carp (Cyprinus carpio). J Zoo Wildl Med. 2014;45:852–858.
2. Bugman AM, Langer PT, Hadzima E, Rivas AE, Mitchell MA. Evaluation of the anesthetic efficacy of alfaxalone in oscar fish (Astronotus ocellatus). Am J Vet Res. 2016;77:239–244.
3. Kischinovsky M, Duse A, Wang T, Bertelsen MF. Intramuscular administration of alfaxalone in red-eared sliders (Trachemys scripta elegans)—effects of dose and body temperature. Vet Anaesth Analg. 2012;40:13–20.
4. Minter LJ, Harms CA, Archibald KE, Broadhurst H, Bailey KM, Christiansen EF, Lewbart GA, Posner LP. Efficacy of alfaxalone for intravascular anesthesia and euthanasia in blue crabs (Callinectes sapidus). J Zoo Wildl Med. 2013;44:694–699.
5. Posner LP, Bailey KM, Richardson EY, Motsinger-Reif AA, Harms CA. Alfaxalone anesthesia in bullfrogs (Lithobates catesbeiana) by injection or immersion. J Zoo Wildl Med. 2013;44:965–971.
6. Sladakovic I, Johnson RS, Vogelnest L. Evaluation of intramuscular alfaxalone in three Australian frog species (Litoria caerulea, Litoria aurea, Litoria booroolongensis). J Herpetol Med Surg. 2014;24:36–42.
7. Villaverde-Morcillo S, Benito J, García-Sánchez R, Martín-Jurado O, Gómez de Segura IA. Comparison of isoflurane and alfaxalone (Alfaxan) for the induction of anesthesia in flamingos (Phoenicopterus roseus) undergoing orthopedic surgery. J Zoo Wildl Med. 2014;45:361–366.