Sildenafil is a vasoactive agent used to treat erectile dysfunction. Sildenafil elevates levels of the second messenger, cGMP, by inhibiting its breakdown via phosphodiesterase type 5 (PDE5) which results in smooth muscle relaxation and inflow of blood to the corpus cavernosum.

Sildenafil is a vasoactive agent used to treat erectile dysfunction. Sildenafil elevates levels of the second messenger, cGMP, by inhibiting its breakdown via phosphodiesterase type 5 (PDE5) which results in smooth muscle relaxation and inflow of blood to the corpus cavernosum.

Tadalafil is an orally adminstered drug used to treat male erectile dysfunction (impotence). It is a Phosphodiesterase type 5 (PDE5) inhibitor; increases the concentrations of cGMP, resulting in relaxation of pulmonary vascular smooth muscle cells and vasodilation of the pulmonary vascular bed.