Which drug is used as an antitussive in dogs?

• A. Diphenoxylate
• B. Hydrocodone
• C. Carfentanil
• D. Codeine

Answer: (D)

Antitussives work by dampening the cough reflex in the brain, with opioids being particularly effective because they act on mu receptors in the medullary cough center to raise the threshold for triggering a cough. Codeine is a mild opioid antitussive that is traditionally used in dogs to suppress nonproductive coughing. It provides cough relief by centrally inhibiting the cough reflex, typically with manageable side effects at antitussive doses.

Diphenoxylate is mainly used as an anti-diarrheal, not a standard antitussive. Carfentanil is an ultra-potent opioid used only in very specific, high-risk scenarios and carries a high risk of respiratory depression, so it is not employed for cough suppression. Hydrocodone also has antitussive effects, but in many veterinary contexts codeine is the classic choice for canine cough, which is why it’s identified as the best answer here.