Sildenafil is often a strong and selective inhibitor of cGMP unique phosphodiesterase type 5 (PDE5) in the corpus cavernosum, where PDE5 is to blame for degradation of cGMP. Sildenafil contains a peripheral web site of action on erections. Sildenafil has no direct relaxant effect on isolated human corpus cavernosum but potently enhances the relaxan