Abstract

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.

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