ORIGINAL RESEARCH—ED PHARMACOTHERAPY A Comparison of the Efficacy and Tolerability of Tadalafil 10 mg and 20 mg in Japanese Patients with Severe Erectile Dysfunction

ABSTRACT Introduction Tadalafil is a phosphodiesterase type 5 inhibitor with documented efficacy in the treatment of erectile dysfunction (ED). Aim To compare the efficacy and tolerability of tadalafil 10 mg and 20 mg in men with severe ED. Methods A prespecified subgroup analysis was conducted to compare the efficacy of tadalafil 10 and 20 mg measured by the International Index of Erectile Function (IIEF) erectile function (EF) domain and Sexual Encounter Profile (SEP) among patients with severe ED (EF domain score = 1–10) in a Japanese placebo-controlled study (PCT). We also analyzed the efficacy of the two doses in men with severe ED post hoc by pooling data from three tadalafil clinical trials that evaluated these doses using a similar study design (three placebo-controlled trials), and evaluated (post hoc) the presence of organic comorbidities in patients with different levels of response to tadalafil 10 or 20 mg. Main Outcome Measures Mean change in the IIEF-EF domain and mean per-patient changes in percent “yes” responses to SEP Question 2 (SEP2) and Question 3 (SEP3). Results Patients with severe ED in the Japanese study experienced numerically greater increases (improvements) when taking tadalafil 20 mg compared with 10 mg in the IIEF-EF domain (14.3 vs. 12.4; P  = 0.355), SEP2 (60% vs. 57%; P  = 0.781), and SEP3 (61% vs. 49%, P  = 0.196). When sufficiently powered, these observations reached statistical significance in the three PCTs: patients with severe ED experienced greater increases when taking tadalafil 20 mg compared with 10 mg in the IIEF-EF domain (13.6 vs. 10.4; P  = 0.014) and SEP3 (56% vs. 43%, P  = 0.019). Both doses were well tolerated. Conclusions Patients with severe ED, and especially those with an organic comorbidity, may derive greater clinical benefits from tadalafil 20 mg compared with 10 mg. Marumo K, Imaoka T, Fujimoto K, Watts S, Stothard D, and McGill J. A comparison of the efficacy and tolerability of tadalafil 10 mg and 20 mg in Japanese patients with severe erectile dysfunction.