Impact of Low Testosterone on Response to Treatment With Tadalafil 5 mg Once Daily for Erectile Dysfunction

OBJECTIVE To evaluate, posthoc, the relationship between serum total testosterone and response to therapy in a study of tadalafil once daily for erectile dysfunction (ED). METHODS Men were aged >= 18 years, with >= 3-month history of ED and partial prior response to on-demand (PRN) phosphodiesterase type 5 inhibitor (PDE5I) therapy. A 4-week maximum-dose PRN PDE5I run-in was followed by a 4-week nondrug washout period, then randomization to tadalafil 2.5 mg titrated to 5 mg or tadalafil 5 mg (pooled for analyses) or placebo once daily for 12 weeks. Analyses compared endpoint efficacy results between low (<300ng/dL) vs normal-testosterone (>= 300ng/dL) level subgroups. RESULTS Improvements for tadalafil vs placebo were significant for the International Index of Erectile Function (IIEF) Erectile Function domain, Intercourse Satisfaction domain, Overall Satisfaction domain, and Question 15 ( confidence in the ability to get and keep an erection; all P<.001), and for the Sexual Encounter Profile Questions 1-5 (all P <=.011). Analysis of covariance modeling identified significant treatment-by-subgroup interactions for the IIEF-Overall Satisfaction domain and erection confidence question and Sexual Encounter Profile Question 3. Comparing between tadalafil-treated testosterone subgroups, the IIEF-Erectile Function domain scores improved significantly more in men with normal vs low testosterone (P=.022); no other significant differences were identified for either placebo or tadalafil. No significant differences in pre-existing conditions were observed between tadalafil and placebo within the normal- and low-testosterone subgroups. CONCLUSION In men with partial response to a PRN PDE5I, tadalafil 5 mg once daily significantly improved ED and sexual function vs placebo irrespective of testosterone levels. (C) 2014 Elsevier Inc.