Dexmedetomidine Mechanism — FRCA Primary MCQ
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Correct answer: A — Alpha-2 adrenergic receptor
Dexmedetomidine is a selective alpha-2 adrenergic receptor agonist. Central alpha-2 receptor activation decreases noradrenergic neuronal firing in the locus coeruleus, producing sedation, and reduces sympathetic noradrenaline release, contributing to bradycardia and hypotension. It also has analgesic- and anaesthetic-sparing effects and is relatively free from respiratory depression when used alone in healthy subjects, although respiratory monitoring remains required clinically. Beta-1 receptor stimulation increases cardiac rate and contractility. GABA-A receptors mediate the effects of agents such as propofol and benzodiazepines, whereas NMDA receptor antagonism is characteristic of ketamine. Mu-opioid receptor agonism explains the principal effects of drugs such as morphine and fentanyl, not dexmedetomidine.
Reference: Electronic Medicines Compendium. Dexmedetomidine 100 micrograms/ml concentrate for solution for infusion, Summary of Product Characteristics, section 5.1 Pharmacodynamic properties, revised 2026. https://www.medicines.org.uk/emc/product/13154/smpc