This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pharmacology
[{'content': 'You decide not to prescribe Sildenafil in a patient because the patient is on an antianginal drug. Which of the following can it be? \nSelect and explain. \nA. Calcium channel blockers, B. Beta blockers, C. Organic nitrates, D. ACE inhibitors', 'role': 'user'}, {'content': 'Answer: C \nExplanation: sildenafil and nitrates are contraindicated to be given in combination since both of them cause vasodilation of vessels and can lead to hypotension. Ref: KD Tripathi 8th ed.', 'role': 'assistant'}]