Vardenafil is a powerful and highly selective PDE5 inhibitor (average inhibitory concentration relative to PDE5 - 0.7 nM). The inhibitory activity of vardenafil on PDE5 is more pronounced than on other known PDEs (15 times more than on PDE6, 130 times more than on PDE1, 300 times more than on PDE11 and 1000 times more than on PDE- 2,3,4,7,8,9,10). Vardenafil increased cGMP in the isolated corpus cavernosum, resulting in smooth muscle relaxation. Vardenafil causes penile erection