AIMTo test the hypothesis that sildenafil (50 mg nightly for one year) can improve spontaneous erectile function (EF) in men with mild-to-moderate arteriogenic erectile dysfunction (ED) responsive to erectogenic treatment.

METHODSIn a prospective open-label trial, 112 men with ED were randomized to sildenafil 50 mg nightly or sildenafil 50 or 100 mg as needed for 12 months, followed by one-month and 6-month non-medicated periods. Non-randomized, non-medicated men with ED were also assessed. The EF domain of the International Index of Erectile Function (IIEF EF) and the peak systolic velocity (PSV) of penile cavernous arteries were used to measure the efficacy.

RESULTSAfter sildenafil treatment and a subsequent non-medicated month, IIEF EF was normal in 29 of 48 (60.4%, 95% confidence interval [CI]: 45.3-74.2%) of the nightly group vs. 4 of 49 (8.2%, 95% CI: 2.3-19.6%) of the as-needed group. PSV improved by 11.2 cm/s (95% CI: 4.7-21.4; P=0.012) in the nightly group but only by 3.4 cm/s (-5.1-14.7; P=0.435) in the as-needed group. IIEF EF normalized in 1 of 18 (5.6%, 95% CI: 0.1-27.3%) non-medicated men and the PSV declined slightly. Six months after treatment, the IIEF EF remained normal and PSV was stabilized in most (28/29, 97%) nightly group men who had initially normalized.

CONCLUSIONSildenafil nightly for one year resulted in ED regression that persisted well beyond the end of treatment, so that spontaneous EF was characterized as normal on the IIEF in most men. The results from this open-label, randomized trial warrant verification under double-blind, placebo-controlled conditions.

Adult ; Dose-Response Relationship, Drug ; Erectile Dysfunction ; drug therapy ; Follow-Up Studies ; Humans ; Male ; Middle Aged ; Penile Erection ; drug effects ; physiology ; Piperazines ; therapeutic use ; Purines ; therapeutic use ; Sildenafil Citrate ; Sulfones ; therapeutic use ; Time Factors ; Treatment Outcome ; Vasodilator Agents ; therapeutic use

AIMNitric oxide (NO)-mediated smooth muscle relaxation causes penile erections. The endothelial NO synthase (eNOS) coenzyme tetrahydrobiopterin (BH4) converts eNOS-mediated catalytic activity from oxygen radical to NO production, improving endothelial function and vascular smooth muscle relaxation.

METHODSUsing quantitative immunohistochemistry, 8-isoprostane and nitrotyrosine concentrations were compared in cavernosal tissue from 17 potent and 7 impotent men, and the effect of single oral doses of BH4 on penile rigidity and tumescence was investigated. The pharmacodynamic effect of single oral doses of BH4 on penile rigidity and tumescence was investigated in a randomized, placebo-controlled, double-blind cross-over fashion in 18 patients with erectile dysfunction (ED) while receiving visual sexual stimulation.

RESULTS8-Isoprostane content in endothelium and smooth muscle was significantly higher in impotent patient samples; the level of nitrotyrosine was unchanged in ED patients. Relative to placebo, a single dose of 200 mg BH4 led to a mean increase in duration of > 60% penile rigidity (33.5 min [95% confidence interval (CI): 13.1-49.3] at base and 29.4 min [95% CI: 8.9-42.2] at tip). A 500-mg dose increased the relative duration of > 60% penile rigidity by 36.1 min (95% CI: 16.3-51.8) at the base and 33.7 min (95% CI: 11.4-43.9) at the tip. Treatments were well tolerated.

CONCLUSIONBH4 treatment is suggested to switch eNOS catalytic activity from super-oxide to NO formation, leading to a reduced formation of free radical reaction product 8-isoprostane without alteration of nitrotyrosine. The observed results make BH4 a suitable candidate as an ED treatment through reconstitution of altered catalytic activity of the eNOS.

Adolescent ; Adult ; Aged ; Biopterin ; analogs & derivatives ; therapeutic use ; Cross-Over Studies ; Dinoprost ; analogs & derivatives ; analysis ; Double-Blind Method ; Erectile Dysfunction ; drug therapy ; Humans ; Immunohistochemistry ; In Vitro Techniques ; Male ; Middle Aged ; Muscle, Smooth, Vascular ; chemistry ; drug effects ; Nitric Oxide ; physiology ; Penile Erection ; physiology ; Penis ; chemistry ; drug effects ; Tyrosine ; analogs & derivatives ; analysis