A randomized, double-blind, placebo-controlled, parallel study to assess the efficacy and safety of once-a-day tadalafil in men with erectile dysfunction who are naïve to PDE5 inhibitors.

Introduction: The majority of subjects included in previous tadalafil once-a-day clinical trials were non-naïve to previous phosphodiesterase 5 (PDE5) inhibitors on demand. A study on PDE5 inhibitor naïve subjects was therefore warranted.

Aim: To evaluate the efficacy and safety of once-a-day tadalafil in PDE5 inhibitor-naïve men with erectile dysfunction (ED).

Main Outcomes Measures: Primary efficacy end points were changes from baseline to end point in the International Index of Erectile Function (IIEF) Erectile Function (EF) domain score and the per-subject proportion of "yes" responses to sexual encounter profile (SEP) question 2 (SEP2) and question 3 (SEP3).

Methods: PDE5 inhibitor-naïve men with ED (N=217) were randomized in a 1:2 ratio to receive placebo or tadalafil 5 mg once a day for 12 weeks. Enrollment began in January 2009 and the last subject completed in January 2010.

Results: At end point, least square mean change from baseline IIEF-EF domain score (7.3 vs. 3.4), SEP2 (23.8% vs. 12.2%) and SEP3 (39.5% vs. 21.5%), was significantly larger for tadalafil vs. placebo (all P<0.001). The most common adverse events (AEs) in tadalafil-treated subjects were back pain, nasopharyngitis, dyspepsia, headache, and myalgia. Four subjects (2.7%) in the tadalafil group and one subject (1.4%) in the placebo group discontinued because of AEs.

Conclusions: In PDE5 inhibitor-naïve men, tadalafil once a day significantly improved EF compared with placebo. Safety results were consistent with previous tadalafil once-a-day clinical trials.