This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
[{'content': 'Sildenafil should not be used in \nSelect and explain. \nA. Diabetics, B. Patients on vasodilator therapy, C. Pulmonary hypertension, D. Erectile dysfunction', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Sildenafil inhibits PDE-5 and prevents Nitric oxide (NO) degradation. Increased NO\xa0results in vasodilation. It should not be used in patients taking vosodilators as it can lead to sudden hypotension.', 'role': 'assistant'}]