Sildenafil
PDE5 inhibitor enhancing nitric oxide-mediated vasodilation in erectile tissue.
Mechanism of Action
Sildenafil is a small-molecule selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). During sexual stimulation, nitric oxide (NO) is released in the corpus cavernosum, activating guanylate cyclase to increase cGMP levels. Sildenafil prevents PDE5 from degrading cGMP, resulting in sustained smooth muscle relaxation and increased blood flow to erectile tissue. Unlike melanocortin agonists, sildenafil acts peripherally on the vascular system rather than centrally on arousal pathways.
Evidence Level
Clinical Trial - Human
1 study published
Pharmacology
Molecular Weight
474.6 Da (free base); 666.7 Da (citrate)
Half-Life
~4 hours
Bioavailability
~40% (oral)