This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sedative-Hypnotics and Parkinsonism, Subject name: Pharmacology
Which orexin receptor antagonist is approved for treatment of insomnia ? 
Select and explain. 
A. Suvorexant, B. Doxepin, C. Ritanserin, D. Agomelatine
A: Suvorexant
Answer: A: Suvorexant 
Explanation: Suvorexant MOA : Orexin 1 and 2 receptors inhibitor Orexin antagonist enhance REM and non-REM sleep. Suvorexant decreases sleep onset latency Dose : 10-mg dose within 30 min of going to bed S/E : Daytime somnolence