Phosphodiesterase type 5 inhibitors: a biochemical and clinical correlation survey

Phosphodiesterase type 5 (PDE 5) is the major cGMP hydrolyzing Enzyme in penile corpus cavernosum and is an important regulator of nitric oxide-mediated smooth muscle relaxation. The critical role of PDE 5 in penile erection and the recent availability of specific and potent inhibitors of PDE 5 have enabled the development of effective oral treatment strategies that have been widely accepted by both health-care professionals and the lay public. This article examines the correlation between the available biochemical and clinical data for the PDE 5 inhibitors sildenafil (Viagra), tadalafil (Cialis) and vardenafil (Levitra).