INI-CET 2021

Q: Which of the following is a centrally acting non-opioid antitussive?

Dextromethorphan. ***Dextromethorphan*** - **Dextromethorphan** is a **centrally acting non-opioid antitussive** that suppresses the cough reflex by acting on the cough center in the medulla oblongata [1], [2]. - It is an **NMDA receptor antagonist** and a **sigma-1 receptor agonist**, which are the primary mechanisms responsible for its antitussive effects [2]. - Unlike opioid antitussives (codeine, hydrocodone), it does **not bind significantly to opioid receptors** at therapeutic doses and therefore lacks addiction potential, respiratory depression, and other opioid side effects [1], [3]. - It is a synthetic morphine analog (dextro-isomer) but is pharmacologically distinct from opioids [1]. *Ambroxol* - **Ambroxol** is a **mucolytic agent** that helps to thin and clear mucus from the respiratory tract. - It works by stimulating serous gland secretion and breaking down mucopolysaccharide fibers, which is different from suppressing the cough reflex centrally. *Guaifenesin* - **Guaifenesin** is an **expectorant** that increases the volume and reduces the viscosity of respiratory tract secretions. - This action helps to make coughs more productive, rather than directly suppressing the cough reflex. *Diphenhydramine* - **Diphenhydramine** is a first-generation **antihistamine** with significant sedative and anticholinergic properties. - While it has some antitussive effects, these are primarily due to its anticholinergic actions causing drying of respiratory secretions and its sedative properties, rather than direct central action on the cough center.

151 Questions — Page 16 of 16

All (151)Anatomy (9)Anesthesiology (4)Biochemistry (11)Community Medicine (12)Dermatology (4)ENT (1)Forensic Medicine (7)Internal Medicine (16)Microbiology (4)Obstetrics and Gynecology (16)Ophthalmology (3)Orthopaedics (3)Pathology (12)Pediatrics (8)Pharmacology (15)Physiology (11)Psychiatry (4)Radiology (4)Surgery (7)

Pharmacology

1 questions

Q151

Which of the following is a centrally acting non-opioid antitussive?