This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pharmacology
Sildenafil acts by inhibiting? 
Select and explain. 
A. PDE 2, B. PDE 5, C. Adenyl cyclase, D. Gaunyl cyclase
B: PDE 5
Answer: B: PDE 5 
Explanation: Sidenafil, verdenafil, tadalafil acts by inhibiting PDE5 they increase NO- increases blood supply to the penis making it erect But they can produce ceain cardiac events They are also used in Pul HTN Ref: KD tripathi 8th ed