Which drug is contraindicated in breeding stallions due to penile prolapse and lowers seizure threshold?

Which drug is contraindicated in breeding stallions due to penile prolapse and lowers seizure threshold?

• A. Acepromazine
• B. Chlorpromazine
• C. Diazepam
• D. Ketamine

Answer: (A)

In breeding stallions, acepromazine is avoided because of its alpha-adrenergic blocking action. By blocking alpha-1 receptors, it reduces sympathetic tone and relaxes smooth muscle, including the retractor penis muscle. This can allow the penis to protrude and remain prolapsed, a problem specific to stallions. At the same time, acepromazine lowers the seizure threshold, increasing the risk of seizures in susceptible animals. The other drugs don’t carry both risks: diazepam tends to raise seizure threshold and isn’t associated with penile prolapse; ketamine isn’t known for causing penile prolapse and doesn’t reliably lower seizure threshold; chlorpromazine is another phenothiazine but the combination of penile prolapse risk and lowered seizure threshold is most classically linked to acepromazine.

In breeding stallions, acepromazine is avoided because of its alpha-adrenergic blocking action. By blocking alpha-1 receptors, it reduces sympathetic tone and relaxes smooth muscle, including the retractor penis muscle. This can allow the penis to protrude and remain prolapsed, a problem specific to stallions. At the same time, acepromazine lowers the seizure threshold, increasing the risk of seizures in susceptible animals. The other drugs don’t carry both risks: diazepam tends to raise seizure threshold and isn’t associated with penile prolapse; ketamine isn’t known for causing penile prolapse and doesn’t reliably lower seizure threshold; chlorpromazine is another phenothiazine but the combination of penile prolapse risk and lowered seizure threshold is most classically linked to acepromazine.