Phenothiazine derivative used as a tranquilizer in preanesthetic mixtures; produces sedation with no significant analgesia and is an antiemetic. contraindicated in breeding stallions because it can cause penile prolapse and in animals with a history of seizures because it lowers the seizure threshold.

• A. Acepromazine
• B. Chlorpromazine
• C. Haloperidol
• D. Promethazine

Answer: (A)

Acepromazine is a phenothiazine tranquilizer widely used as a preanesthetic sedative. It provides calming and sedative effects with little to no analgesia, and it also has antiemetic properties, making it helpful during anesthesia induction. Its mechanism involves blocking dopamine receptors in the CNS, along with alpha-1 adrenergic blockade that can cause vasodilation and potential hypotension. A key clinical caution is that it relaxes penile tissue in stallions, leading to penile prolapse, which is why it’s contraindicated in breeding stallions. It also lowers the seizure threshold, so it’s used cautiously in animals with a history of seizures. Among the options, this drug best fits all the described features and uses.