Co-Administering Testosterone With PDE5 Inhibitors in ED Patients Non Responders to PDE5 Inhibitors Alone

30 to 50% of the patients presenting with Erectile Dysfunction (ED) do not respond to PDE V Inhibitor therapy, which is presently considered as the first choice treatment for most ED patients. Recent reports stated a high prevalence of low serum testosterone levels in such non responders, and an improvement of their response by combining testosterone therapy with the PDE V Inhibitor. This suggests there may be a minimum threshold level of blood testosterone for a full effectiveness of PDE V Inhibitor therapy. Two double blind, placebo controlled studies have added support to this hypothesis but one involved only 20 patients while in the other the benefit of combining testosterone was transient. This is a multi-centric study, double blind placebo controlled and randomized as concerns testosterone administration, that aims to objectively assess the efficacy of co-administering testosterone with the PDE 5 inhibitor Tadalafil to improve the erectile function of a large group of ED patients non-responders to PDE V inhibitors alone. Patients will be screened to ensure inclusion and exclusion criteria completion, including a serum testosterone level \< 4 ng/ml for total testosterone or \< 1 ng/ ml for bioavailable testosterone. They will then enter a four week run-in period in the meanwhile they will receive Tadalafil 10 mg only, once daily, in order to confirm their non responsiveness to PDE V inhibitors and their eligibility to enter the treatment phase based on IIEF scoring, SEP diaries and a Global Assessment Question (GAQ). The patients still non responders after 4 weeks of Tadalafil 10 mg daily will enter a 12 weeks treatment phase including visits at weeks 4, 8, 12 and 16. Treatment procedure will include: 1. continuation of Tadalafil at 10 mg dose daily followed by routine assessment using SEP diaries, IIEF scoring, GAQ and Aging Male Symptoms scale administered at each study visit. Safety assessments will be performed in addition during the last visit (physical ex