This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System, Subject name: Pharmacology
[{'content': 'Sildenafil, a gra like medicine, can be used for which of the following conditions? \nSelect and explain. \nA. Pulmonary hypeension, B. Essential hypeension, C. Malignant hypeension, D. Hypeension in pregnancy', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Phosphodiesterase inhibitors like sildenafil are indicated in Erectile dysfunction (Drug of choice) and Pulmonary hypeension Sildenafil selectively inhibits Phosphodiesterase (PDE)-V leading to increased cGMP levels and so is useful in erectile dysfunction. It can be administered orally. Adverse effects include headache, nasal congestion, flushing, visual disturbances (blue vision) etc. Colour vision defect is due to inhibition of PDE-VI present in the retina. Apa from their use in ED, sildenafil can also be used in the management of pulmonary hypeension. Other drugs of this group are vardenafil, udenafil, avanafil and tadalafil. Tadalafil- PDE-6 inhibition is not present', 'role': 'assistant'}]