PDE5 inhibitors primarily affect which vascular bed?

• A. Pulmonary vasculature
• B. Renal vasculature
• C. Cerebral arteries
• D. Coronary arteries

Answer: (A)

PDE5 inhibitors boost the NO–cGMP pathway in smooth muscle by preventing the breakdown of cGMP, so vascular smooth muscle relaxes when NO is present. In the pulmonary arteries, this mechanism directly translates to vasodilation and a reduction in pulmonary vascular resistance, which is the key therapeutic goal in pulmonary arterial hypertension. That primary action on the pulmonary vasculature is why this option is the best answer. While systemic effects can occur, the most clinically important and characteristic effect of PDE5 inhibitors lies in the pulmonary circulation. The other vascular beds listed aren’t the main target for the typical use of these drugs.