Which alpha-2 agonist is approved for use in dog, cat, horse, elk, deer and used for sedative, analgesic, anesthetic, and as an emetic?

• A. Xylazine
• B. Edrophonium
• C. Guaifenesin
• D. Sevoflurane

Answer: (A)

Alpha-2 adrenergic agonists produce sedation and analgesia by activating receptors in the central nervous system, which dampens sympathetic activity and pain signaling. Xylazine is the classic veterinary alpha-2 agonist and is approved for use in a wide range of species, including dogs, cats, and horses, with additional use in wildlife such as elk and deer. It provides calm, analgesia, and can serve as part of anesthesia protocols, and it also has an emetic effect in cats, illustrating its central action that can trigger vomiting in some species. The other drugs do not share this mechanism or clinical profile: edrophonium is a cholinesterase inhibitor used to diagnose or reverse certain neuromuscular conditions; guaifenesin is an expectorant/muscle relaxant used in some anesthesia contexts but not an alpha-2 agonist; sevoflurane is an inhaled anesthetic, not an alpha-2 agonist. Therefore, the alpha-2 agonist that matches the described uses is xylazine.