Dextromethorphan-quinidine is listed as potentially inappropriate in older adults. What is its primary clinical use?

• A. Antitussive
• B. Antihistamine
• C. Expectorant
• D. Decongestant

Answer: (A)

The main purpose of dextromethorphan-quinidine is to suppress coughing. Dextromethorphan acts on the brain’s cough center to reduce the cough reflex, so the combination is used as an antitussive for persistent or refractory cough. Quinidine is included to increase dextromethorphan levels by inhibiting its metabolism, but the clinical effect remains cough suppression. It is not an antihistamine, an expectorant, or a decongestant. In older adults, Beers criteria flag this combo as potentially inappropriate mainly because of safety concerns (such as risk of heart rhythm issues and CNS side effects, plus drug interactions), even though its primary use is antitussive therapy.