What is suvorexant and its mechanism?

• A. Orexin receptor antagonist that inhibits orexin A/B signaling to promote sleep.
• B. GABA-A receptor positive allosteric modulator with high anxiolytic effect.
• C. Histamine H1 receptor antagonist used for allergy.
• D. Dopamine D2 receptor agonist used for Parkinson's.

Answer: (A)

Suvorexant works by blocking the brain’s wake-promoting system. It is a dual orexin receptor antagonist, meaning it binds to and inhibits both orexin receptors (OX1 and OX2) that orexin A and orexin B activate to promote arousal. By blocking these signals, the overall arousal drive decreases, helping with sleep onset and maintenance. This mechanism is different from classic sleep aids that enhance GABA-A activity or other targets like histamine or dopamine. So suvorexant promotes sleep by dampening orexin-mediated wakefulness rather than by broadly depressing the CNS.