Aim: To determine the effect of sildenafil citrate on the nocturnal penile erections (i.e. time to onset, the duration of erection, and the interval between first and second erections) of healthy young men.

Methods: Twenty-two potent men, 23–29 years old, were recruited for the study. All subjects completed three sessions over consecutive nights using the RigiScan monitoring device (Dacomed, Minneapolis, USA). After a first night of adaptation, night 2 records were their baseline values, and on night 3 they received 100 mg of sildenafil citrate. Statistical comparisons were done between the second and third night data.

Results: The mean time to onset of the first erection with sildenafil citrate was (34±18) min, whereas it was (74±24) min (P < 0.001) without sildenafil citrate. The number of erections observed during the first 5 h after sildenafil citrate medication was 3.6±0.5 in contrast to 2.4±0.5 with no medication (P = 0.001). The interval between first and second erections was shorter with sildenafil citrate: (52±26) min vs. (85±34) min (P = 0.01). The duration of the last erection was statistically significantly longer with the sildenafil citrate: (64±33) min vs. (42±28) min (P < 0.01).

Conclusion: Healthy young men achieved erection within 34 min after sildenafil citrate administration, which is shorter than the 1 h interval proposed by the manufacturer. The interval between the first and second erections was shorter and the duration of the last nocturnal erection was longer.

Keywords: sildenafil citrate, nocturnal erection, nocturnal penile tumescence, rigidity testing, erectile dysfunction

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