<p>Sildenafil is a selective inhibitor of cyclic Guanosine Monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5) used for treatment of erectile dysfunction. Danafil (Sildenafil) enhances the effect of nitric oxide (NO) by inhibiting phosphodiesterase type 5 (PDE5), which is responsible for degradation of cGMP in the corpus cavernosum that results in smooth muscle relaxation and inflow of blood to the corpus cavernosum.</p>