To determine the minimal time to successful intercourse after taking sildenafil citrate for erectile dysfunction (ED).

Male patients with ED (mean age 60 years; mean ED duration 7.0 years) who were successfully treated with sildenafil (100 mg) for 2 months or longer were randomized to sildenafil (n = 115) or placebo (n = 113) for 4 weeks of double-blind treatment. Using a stopwatch, patients recorded the time needed to obtain an erection hard enough for sexual intercourse after taking the study drug at least 2 hours after eating.

Within 14 and 20 minutes of sildenafil dosing, 35% and 51% of sildenafil-treated patients, respectively, versus 22% and 30% of placebo-treated patients, respectively, had an erection that led to successful intercourse (P <0.05 for both). The median time to erection leading to successful intercourse after sildenafil dosing was 36 minutes compared with 141 minutes for placebo.

In this study, slightly more than one half of a population of prior sildenafil responders achieved an erection that led to successful sexual intercourse within 20 minutes of sildenafil administration, suggesting that the onset of action of sildenafil can be less than 30 minutes in men with ED.