Effect of testosterone replacement on response to sildenafil citrate in men with erectile dysfunction: a parallel, randomized trial.

Background: Erectile dysfunction and low testosterone levels frequently occur together.

Objective: To determine whether addition of testosterone to sildenafil therapy improves erectile response in men with erectile dysfunction and low testosterone levels.

Design: Randomized, double-blind, parallel, placebo-controlled trial. (ClinicalTrials.gov registration number: NCT00512707)

Setting: Outpatient academic research center.

Participants: Men aged 40 to 70 years with scores of 25 or less for the erectile function domain (EFD) of the International Index of Erectile Function, total testosterone levels less than 11.45 nmol/L (<330 ng/dL), or free testosterone levels less than 173.35 pmol/L (<50 pg/mL).

Intervention: Sildenafil dose was optimized, and 140 participants were then randomly assigned to 14 weeks of daily transdermal gel that contained 10-g testosterone for 70 participants and placebo for the remaining 70 participants. All participants were included in the primary analysis, although 10 in the testosterone group and 12 in the placebo group did not complete the study.

Results: At baseline, the 2 groups had similar EFD scores. Administration of sildenafil alone was associated with a substantial increase in EFD score (mean, 7.7 [95% CI, 6.5 to 8.8]), but change in EFD score after randomization did not differ between the groups (difference, 2.2 [CI, -0.8 to 5.1]; P = 0.150). The findings were similar for other domains of sexual function in younger men, more obese men, and men with lower baseline testosterone levels or an inadequate response to sildenafil alone. Frequency of adverse events was similar for testosterone and placebo groups.

Limitation: Whether testosterone could improve erectile function without sildenafil was not studied.

Conclusion: Sildenafil plus testosterone was not superior to sildenafil plus placebo in improving erectile function in men with erectile dysfunction and low testosterone levels.

Primary Funding Source: National Institute of Child Health and Human Development.