Effect of Chronic Sildenafil Treatment on Penile Endothelial Function: A Randomized, Double-Blind, Placebo Controlled Study

Abstract

Although the effect of phosphodiesterase type 5 inhibitors on endothelial function in the systemic circulation has been extensively studied, its effect on penile endothelial function remains unexplored. Therefore, we evaluated the effect of daily sildenafil on penile endothelial function. A total of 60 patients with erectile dysfunction were randomized blindly to daily placebo or 50 mg sildenafil for 4 weeks. Penile and forearm blood flow as well as endothelial function indices were measured at baseline and after 4 weeks using venoocclusive strain gauge plethysmography for both organs. Sequential changes in flow, maximal blood flow and area under the curve induced by reactive hyperemia after 5 minutes of transient ischemia were considered indices of endothelial function. There were 34 patients treated with sildenafil and 19 on placebo who completed the study. The general characteristics of both groups were comparable. Mean +/- SEM baseline penile blood flow was 6.2 +/- 1.4 and 7.0 +/- 0.6 ml/dl per minute for the placebo and sildenafil groups, respectively (p = 0.54). Baseline forearm blood flow was similar in both groups. At baseline penile AUC was 420 +/- 50 and 520 +/- 50 (p = 0.18), and in the forearm it was 445 +/- 40 and 410 +/- 40 (p = 0.45) for the placebo and sildenafil groups, respectively. After 4 weeks on the assigned drug penile blood flow increased to 11.2 +/- 2 ml/dl per minute in the sildenafil group (p = 0.02) and remained unchanged in the placebo group. After 4 weeks penile AUC increased to 720 +/- 65 in the sildenafil group (0.04) and remained unchanged in the placebo group. Placebo and sildenafil did not affect the indices of forearm endothelial function. Daily sildenafil significantly improves penile blood flow and penile endothelial function indices without causing any relevant systemic effects.