Which skeletal muscle relaxant is used in combination with ketamine and xylazine in horses to induce general anesthesia and is also used as an expectorant?

• A. Pilocarpine
• B. Guaifenesin
• C. Aminopentamide
• D. Potassium Bromide

Answer: (B)

The idea being tested is that guaifenesin serves as a skeletal muscle relaxant in equine anesthesia and also acts as an expectorant. In horses, a common induction regimen combines ketamine and xylazine with guaifenesin to achieve smooth, deeper muscle relaxation while the animal is under anesthesia; ketamine provides dissociative anesthesia and xylazine adds analgesia and sedation, and guaifenesin relaxes skeletal muscles to reduce resistance and improve intubation conditions. At the same time, guaifenesin acts as an expectorant, thinning and helping clear mucus in the airways. The other substances listed do not have both roles: pilocarpine is a cholinergic agent not used for muscle relaxation or as an expectorant; aminopentamide is an anticholinergic used for GI spasms; potassium bromide is an anticonvulsant.