Objective: Diabetic patients have a reduced endothelial response to phosphodiesterase-5 inhibitors. The aim of this study was to determine the effects of chronic therapy with sildenafil on endothelial function in patients with Type 2 diabetes mellitus (DM2).
Methods: In a double-blind, placebo-controlled parallel design, 20 patients without erectile dysfunction randomly received a loading dose of sildenafil (100 mg) for 3 days, followed by either sildenafil 25 mg three times a day (t.d.s.) for 4 weeks or sildenafil 25 mg t.d.s. for 4 days followed by placebo t.d.s. for 3 weeks.
Results: After 1 week, flow-mediated dilatation (FMD) improved significantly (> 50% compared with baseline) in patients allocated to both sildenafil arms (62 and 64%, respectively). In patients allocated to chronic sildenafil, a progressive increase in percentage of patients with FMD improvement was noted (78, 86 and 94% at 2, 3 and 4 weeks, respectively) while a progressive decrease in the placebo group occurred (45, 18 and 6% at 2, 3 and 4 weeks, respectively). At the end of the study, a significant improvement in FMD compared with baseline was noted after chronic sildenafil (FMD from 6.8 +/- 0.5 to 12.5 +/- 0.7%, P = 0.01 vs. baseline). A decrease in endothelin-1 levels and an increase in nitrite/nitrate levels were found after chronic sildenafil; significant changes from baseline in C-reactive protein, interleukin 6, intercellular adhesion molecule and vascular adhesion molecule levels were also found.
Conclusions: In DM2 patients, daily sildenafil administration improves endothelial function and reduces markers of vascular inflammation, suggesting that the diabetes-induced impairment of endothelial function may be improved by prolonged phosphodiesterase-5 inhibition.