7. Distinguishing psychogenic and organic ED Droupy S et al. (2006) How, why and when should urologists evaluate male sexual function? Nat Clin Pract Urol 3: 84 â 94 doi:10.1038/ ncpuro406
15. Comparison of sildenafil, vardenafil, tadalafil PDE5 inhibitor Duration Sildenafil 12 hours Vardenafil 4-5 hours Tadalafil 36 hours Vardenafil, however, is the most potent (lowest maximal concentration) and binds to PDE5 more rapidly than the others, thus it has a potential time of onset of 10 minutes.