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Urology. 2000 Dec 20;56(6):906-11.

Sildenafil taken at bedtime significantly increases nocturnal erections: results of a placebo-controlled study.

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  • 1Institute of Human Anatomy, University of Milan School of Medicine, Milan, Italy.



Nighttime erections occur at all ages and contribute to the maintenance of the morphodynamic integrity of smooth muscle cells within the corpora cavernosa. This study was aimed at evaluating the effect on nocturnal erections of sildenafil versus a placebo taken at bedtime.


A double-blind, crossover, placebo-controlled study design was used to examine the effects of sildenafil and placebo on sleep-related erectile activity. Thirty selected patients with erectile dysfunction (vasculogenic etiology, 22 patients [73%]; psychogenic etiology, 8 patients [27%]) were submitted to a polysomnographic recording of nocturnal erections, using a RigiScan device during 3 consecutive nights. After a first night of adaptation, the 2 following nights were used to study patients after the administration of sildenafil (100 mg) or a placebo taken at bedtime.


Twenty-three patients (77%) showed a significantly improved nocturnal erectile activity (according to the calculation of rigidity and tumescence activity units) after the administration of sildenafil (P <0.01), 5 patients (17%) showed comparable nocturnal erections with sildenafil and placebo, and 2 patients (6%) showed a significantly improved nocturnal erectile activity after taking the placebo (P <0.05). Overall, mean rigidity and tumescence activity values at the tip and base of the penis were significantly improved after sildenafil rather than placebo administration (P <0.001). The duration of tip rigidity greater than 60% was significantly longer during the night with sildenafil (P <0. 001). Although the number of erectile episodes was greater during the sildenafil night, this did not reach statistical significance.


In most patients with good sleep efficiency and who have erectile dysfunction, sildenafil, rather than a placebo, taken at bedtime produces a significantly improved nocturnal erectile activity. Further studies are needed to verify whether this preliminary finding may constitute the basis for the use of sildenafil as a tool for preventing erectile dysfunction.

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