Phosphodiesterase 5 inhibitors and erectile dysfunction

Background: The introduction of phosphodiesterase 5 (PDE5) inhibitors for the treatment of erectile dysfunction was a landmark in the therapy of this highly prevalent male disorder. After the launch of sildenafil in 1998, which was followed by vardenafil and tadalafil in 2003, > 40 million men worldwide have been treated with these compounds. It turned out that erectile dysfunction treatment with PDE5 inhibitors is not only very effective, but also well tolerated and safe. Objective: As the erectile dysfunction market is still growing, new developments have been initiated, addressing mainly pharmacokinetic parameters by new compounds, reformulations of the available drugs and combinations of PDE5 inhibitors with other treatment principles. This review summarises and updates the patent information and the present status of developments within the world of PDE5 inhibitors for the treatment of erectile dysfunction. Methods: The information was collected from various scientific databases (e.g., Dolphin, IDDB, Integrity Prous Science, Medline, chemical abstracts, ClinicalTrials.gov) focused on the literature from 2002 onwards. Results/conclusion: Because of the high standard in erectile dysfunction therapy with existing PDE5 inhibitors, positioning of new PDE5 inhibitors for the treatment of erectile dysfunction will become very difficult. Combinations with new drugs having a different mode of action could be successful in patients presently resistant to the therapy with PDE5 inhibitors. The use of PDE5 inhibitors within other indications beyond erectile dysfunction has become an important new aspect in the development of these drugs and will have a substantial influence on research and development within this unique class of drugs.