Effects of sildenafil (Viagra (TM)) administration on seminal parameters and post-ejaculatory refractory time in normal males

Sildenafil is a specific inhibitor of phosphodiesterase (PDE) type 5 and re presents a powerful therapy for male erectile dysfunction (ED) of different aetiology. Recently, sildenafil has been shown to restore erections in tem porary ED related to the need of semen collection for assisted reproductive techniques. In this study, we investigated whether sildenafil administrati on modifies seminal parameters and/or erectile function in normal healthy v olunteers. In a double-blind, randomized, placebo-controlled, cross-over tw o period investigation we enrolled 20 healthy male volunteers (mean +/- SE age 32 +/- 0.5 years). Subjects were not using any medication for the 3 mon th period prior to the study and were engaged in a stable relationship with proven fertility, The effects of sildenafil (100 mg) on seminal parameters and erectile function after audiovisual sexual stimulation were evaluated by semen analysis and by colour-Duplex ultrasound (the Resistive Index) res pectively, In all subjects, sildenafil caused no changes in seminal and ere ction parameters when compared to placebo. Interestingly, sildenafil admini stration led to a marked reduction of the postejaculatory refractory time ( 10.8 +/- 0.9 min versus 2.6 +/- 0.7 min for placebo and sildenafil respecti vely; P < 0.0001), These results indicate that in normal subjects acute sil denafil treatment does not modify semen characteristics and has a positive influence over the resumption of erections following ejaculation in the pre sence of a continuous erotic stimulus.