Introduction. Addition of testosterone (T) may improve the action of phosphodiesterase type 5 inhibitors (PDE5-Is) in patients with erectile dysfunction not responding to PDE5-Is with low or low-normal T levels.
Aims. To confirm this add-on effect of T in men optimally treated with PDE5-Is and to specify the baseline T levels at which such an effect becomes significant.
Methods. A multicenter, multinational, double-blind, placebo-controlled study of 173 men, 45–80 years, nonresponders to treatment with different PDE5-Is, with baseline total T levels ≤4 ng/mL or bioavailable T ≤ 1 ng/mL. Men were first treated with tadalafil 10 mg once a day (OAD) for 4 weeks; if not successful, they were randomized in a double-blind, placebo-controlled design to receive placebo or a 1% hydroalcoholic T gel (50 mg/5 g gel), to be increased to 10 mg T if results were clinically unsatisfactory.
Main Outcomes Measures. Mean change from baseline in the Erectile Function Domain Score of the International Index of Erectile Function and rate of successful intercourses (Sexual Encounter Profile 3 question).
Results. Erectile function progressively improved over a period of at least 12 weeks in both the placebo and T treatment groups. In the overall population with a mean baseline T level of 3.37 ± 1.48 ng/mL, no additional effect of T administration to men optimally treated with PDE5-Is was encountered. The differences between the T and placebo groups were significant for both criteria only in the men with baseline T ≤3 ng/mL.
Conclusions. The maximal beneficial effects of OAD dosing with 10 mg tadalafil may occur only after as many as 12 weeks. Furthermore, addition of T to this PDE5-I regimen is beneficial, but only in hypogonadal men with baseline T levels ≤3 ng/mL. Buvat J, Montorsi F, Maggi M, Porst H, Kaipia A, Colson MH, Cuzin B, Moncada I, Martin-Morales A, Yassin A, Meuleman E, Eardley I, Dean JD, and Shabsigh R. 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). J Sex Med 2011;8:284–293.