This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Pharmacology
You decide not to give sildenafil to patient who is on antianginal drug, which of the following drug it can be? 
Select and explain. 
A. Calcium channel blockers, B. Beta blockers, C. Nitrates, D. ACE inhibitors
C: Nitrates
Answer: C: Nitrates 
Explanation: Ans. C. NitratesNitrates act by increase CGMP and sildenafil decrease the breakdown of this compound. Marked increase in CGMP results in profound hypotension and reflex tachycardia.