Which description matches tadalafil's target with its effect?

• A. Inhibits PDE5 causing increased cGMP and vasodilation
• B. Inhibits PDE3 causing increased cAMP
• C. Inhibits PDE2 causing decreased cGMP
• D. Inhibits PDE4 causing anti-inflammatory effects

Answer: (A)

Tadalafil works by selectively blocking a enzyme that breaks down a signaling molecule involved in smooth muscle relaxation. In the penis, when sexual stimulation occurs, nitric oxide activates guanylate cyclase to raise cGMP. This cGMP causes smooth muscle relaxation and increases blood flow, producing an erection. PDE5 normally breaks down cGMP, so inhibiting PDE5 keeps cGMP levels elevated and enhances the NO-driven relaxation and vasodilation.

That’s why the description that matches tadalafil is inhibiting PDE5 to raise cGMP and promote vasodilation. The other options point to different enzymes and messengers (PDE3 raising cAMP, PDE2 lowering cGMP, PDE4 producing anti-inflammatory effects), which is not tadalafil’s target.