Hypogonadal men nonresponders to the PDE5 inhibitor tadalafil benefit from normalization of testosterone levels with a 1% hydroalcoholic testosterone gel in the treatment of erectile dysfunction (TADTEST study). Buvat J, Montorsi F, Maggi M, et al. J Sex Med 2011;8(1):284-293.
May 20th, 2011
This study aimed to confirm that testosterone replacement therapy (Testogel®, Androgel®) improved erectile function in men with erectile dysfunction (ED) who were nonresponders to phosphodiesterase type 5 inhibitors (PDE5-Is). The study also investigated the impact of baseline testosterone levels on response to treatment. The multicentre, multinational, double-blind, placebo-controlled study (TADTEST) included 173 men (age 45–80 years) with baseline total testosterone levels ≤400 ng/dL or bioavailable testosterone ≤100 ng/dL and inadequate response to 4 weeks of treatment with the PDE5-I tadalafil (Cialis®) 10 mg once a day. Once-daily tadalafil treatment was continued for an additional 12 weeks and men were randomized also to receive placebo or testosterone 50 mg once daily in the form of a 1% hydro-alcoholic gel, to be increased to 100 mg if results were unsatisfactory. The Erectile Function Domain (EFD) Score of the International Index of Erectile Function (IIEF) and rate of successful intercourse attempts were the main outcomes measured.1
What is known
Failure to respond to treatment with PDE5-Is occurs in approximately a third of men with ED.1 As the pharmacological activity of PDE5-Is appears from animal studies3-5 and in humans6 to be androgen-dependent, non-response to PDE5-Is may be explained at least in part by testosterone deficiency. Furthermore, testosterone deficiency has been shown to predict a poor response to PDE5-Is,7-13and the addition of testosterone replacement therapy to a PDE5-I appears from non-comparative studies to improve erectile function in men with low testosterone.7-10,12
However, data from randomised, placebo-controlled trials have been limited. This multicentre controlled study was designed to test whether the action of PDE5-Is in men is androgen-dependent and to investigate whether a threshold value exists for the additive effect of testosterone on PDE5-I therapy.
What this study adds
This study provides supporting evidence that ED patients with low testosterone levels (≤300 ng/dL [10.4 nmol/L] total testosterone) treated with a PDE5-I benefit from the addition of testosterone replacement therapy. It should be noted that a once-daily dosage of tadalafil 10 mg was used in this study, which is the recommended starting dose of tadalafil for use as needed in most patients, and is higher than the 5 mg dose approved for once-daily administration since the study was designed. Nevertheless, the study shows that testosterone replacement therapy (in this case testosterone gel) is beneficial in improving the response of ED therapy in men with hypogonadism.
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