COMPARISON OF SUBCUTANEOUS ALFAXALONE AND SUBCUTANEOUS ALFAXALONE-DEXMEDETOMIDINE FOR SEDATION IN THE HOUSTON TOAD (ANAXYRUS HOUSTONENSIS)

The Houston toad (Anaxyrus houstonensis), a primarily terrestrial amphibian of south-central Texas, has been listed as federally endangered since 1970. Sedation is an important tool for obtaining diagnostics and providing treatment in this species. This prospective, randomized, and blinded study compared the sedative effects of SC alfaxalone (Protocol A) at approximately 12 mg/kg (median [range] ¼ 12.70 [12.09-13.95] mg/kg] to SC alfaxalone-dexmedetomidine (Protocol AD) at approximately 12 mg/kg (median [range] ¼ 12.68 [12.16-13.56] mg/kg) and 0.1 mg/kg (median [range] ¼ 0.1 [0.07-0.13] mg/kg), respectively, in adult Houston toads (n ¼ 26). Toads from Protocol AD received atipamezole SC at approximately 1 mg/kg (median [range] ¼ 0.96 [0.75-1.25] mg/kg) 45 min postinduction, whereas toads from Protocol A received the equivalent volume of SC sterile saline at the same time point. Heart rate, gular rate, and times to first effect, loss of righting reflex, ability to position for radiographs, loss of nociception, return of righting reflex, and full recovery were recorded. A significantly greater number of toads lost righting reflex, positioned for radiographs, and lost nociception with Protocol AD compared with Protocol A. Additionally, time to return of righting reflex and time to full recovery were significantly longer with Protocol AD than with Protocol A. The protocols did not differ significantly in time to first effect, time to radiographic positioning, or time to loss of nociception. Histologic examination of four toads euthanized during the study revealed acute injection site reactions from all administered drugs, including saline. No clinical adverse reactions were observed. This study demonstrates that the combination of SC alfaxalone and dexmedetomidine results in deeper sedation than SC alfaxalone alone, but also correlates with longer recovery times despite antagonist administration.