A Return to Normal Erectile Function with Tadalafil Once Daily after an Incomplete Response to As-Needed PDE5 Inhibitor Therapy


  • Acknowledgments of financial support: The trial is registered at ClinicalTrials.gov, number NCT01130532. This study was funded by Eli Lilly and Company.



An optimal outcome of an erectile dysfunction (ED) treatment is to enable a return to normal erectile function (as defined by an International Index of Erectile Function—Erectile Function [IIEF-EF] domain score ≥26). As-needed (PRN) phosphodiesterase type 5 (PDE5) inhibitor treatment does not always result in a return-to-normal erectile function.


The combined studies evaluated whether treatment with tadalafil once daily would allow men to return to normal erectile function who had less than normal IIEF-EF domain scores while using a maximum dose of a PRN PDE5 inhibitor treatment.


Men were ≥18 years of age, sexually active, reported a ≥3-month history of ED, and had been taking the maximum dose of sildenafil citrate, vardenafil, or tadalafil PRN. Randomization to once-daily therapy with tadalafil 2.5 mg to 5 mg (N = 207), tadalafil 5 mg (N = 207), or placebo (N = 209) for 12 weeks followed a 4-week maximum dose PRN PDE5 treatment and 4-week nondrug lead periods. Two identical double-blind, randomized, placebo-controlled studies were conducted; combined results are reported.

Main Outcome Measure

The main outcome measure was the percentage of subjects with a return-to-normal erectile function (IIEF-EF domain score ≥ 26) when treated with tadalafil once daily compared with placebo.


In subjects not achieving normal erectile function with the maximum dose of a PRN PDE5 inhibitor, a higher percentage of subjects treated with tadalafil had an IIEF-EF domain score ≥26 at end point (tadalafil 2.5- to 5-mg group [39%]; tadalafil 5-mg group [40%]) compared with the placebo group (12.1%; P < 0.001). Tadalafil was generally well tolerated and adverse events observed were consistent with previous reports of tadalafil once daily.


Treatment with tadalafil once daily significantly improved erectile function in men with mild to mild-moderate impairments in erectile function following PRN PDE5 inhibitor treatment. Kim ED, Seftel AD, Goldfischer ER, Ni X, and Burns PR. A return to normal erectile function with tadalafil once daily after an incomplete response to as-needed PDE5 inhibitor therapy. J Sex Med 2014;11:820–830.