Phosphodiesterase inhibitors in the treatment of erectile dysfunction.

Based on knowledge of intracellular signal propagation in cavernous smooth muscle tone regulation and the development of new and selective pharmacological agents, selective phosphodiesterase (PDE) inhibitors were recently introduced for the treatment of erectile dysfunction. By molecular biological methods, PDE isoenzymes III, IV and V were characterized in the human cavernous smooth muscles. In functional organ bath studies using precontracted human cavernous tissue strips, PDE III and V inhibitors showed the most pronounced relaxant responses. In clinical studies, the use of the orally active PDE V inhibitor sildenafil induced a pronounced and significant erectogenic effect in patients with both predominantly psychogenic and organogenic etiology of erectile dysfunction. The first promising clinical data on the use of an orally active PDE inhibitor for the treatment of erectile dysfunction are well supported by consistent basic science findings. Further research will possibly allow to identify diagnostic tools for erectile dysfunction and for even more selective drugs in its therapy.