Evaluation of the efficacy and safety of once-a-day dosing of tadalafil 5mg and 10mg in the treatment of erectile dysfunction: results of a multicenter, randomized, double-blind, placebo-controlled trial.

Background: Erectile dysfunction (ED) is a chronic disease; however, therapy is currently administered as needed with oral phosphodiesterase 5 (PDE5) inhibitors like tadalafil. Because the 17.5-h half-life of tadalafil enables therapeutic plasma levels to be sustained with daily administration, tadalafil is a good candidate for once daily dosing therapy.

Methods: This multicenter, randomized, double-blind, placebo-controlled, parallel-group, 12-week study enrolled 268 men 1:2:2 to placebo, tadalafil 5mg, and tadalafil 10mg taken once daily. Primary efficacy measures included changes in the International Index of Erectile Function Erectile Function domain (IIEF EF), Sexual Encounter Profile diary Questions 2 (SEP2: successful penetration), and 3 (SEP3: successful completion of intercourse), and tolerability. Secondary measures included percentage of patients at endpoint who reported improved erectile function (EF), and percentage who reported "no ED" (IIEF EF score 26-30).

Results: For patients who took placebo, tadalafil 5mg, and tadalafil 10mg, changes from baseline to endpoint were, respectively, 0.9, 9.7, and 9.4 for IIEF EF; 11.2, 36.5, and 39.4 for SEP2; and 13.2, 45.5, and 50.1 for SEP3. At endpoint, 28.3%, 84.5%, and 84.6% reported improved erections, and 8.3%, 51.5%, and 50.5% reported "no ED," respectively. All comparisons between tadalafil and placebo were significant (p<0.001). Adverse events that occurred in at least 5% of patients were dyspepsia, headache, back pain, upper abdominal pain, and myalgia; nine patients (3.4%) discontinued because of adverse events.

Conclusions: Once-a-day tadalafil 5mg or 10mg was well tolerated and significantly improved EF in men with ED.