<prompt> You decide not to give sildenafil to patient who is on antianginal drug, which of the following drug it can be?Calcium channel blockersBeta blockersNitratesACE inhibitors  <response>: 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. 