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
Sildenafil should not be used in 
Select and explain. 
A. Diabetics, B. Patients on vasodilator therapy, C. Pulmonary hypertension, D. Erectile dysfunction
B: Patients on vasodilator therapy
Answer: B: Patients on vasodilator therapy 
Explanation: Sildenafil inhibits PDE-5 and prevents Nitric oxide (NO) degradation. Increased NO results in vasodilation. It should not be used in patients taking vosodilators as it can lead to sudden hypotension.