Which drug is used as an antitussive in dogs and is an opioid?

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

Answer: (B)

Opioids suppress coughing by acting on the medullary cough center in the brain, raising the threshold for coughing. Codeine is a relatively mild opioid that is used as an antitussive in dogs because it is converted to morphine in the body, providing central cough suppression at antitussive doses with a relatively tolerable side‑effect profile. It’s a classic veterinary option for reducing coughing through this central mechanism.

Apomorphine is used to induce vomiting, not to suppress cough. Diphenoxylate is mainly employed as an antidiarrheal and its antitussive use is not the standard focus in veterinary practice. Hydrocodone does have antitussive and analgesic effects, but the question highlights the traditional veterinary antitussive opioid, which is codeine.