Effects of sildenafil (Viagra) administration on seminal parameters and post-ejaculatory refractory time in normal males.
Level 2 - randomized trial
Randomized, double-blind, placebo-controlled crossover trial
PubMed 10611201 · doi:10.1093/humrep/15.1.131
What was done
A double-blind, randomized, placebo-controlled, two-period crossover trial evaluated the effects of acute oral sildenafil (100 mg) versus placebo in 20 healthy, fertile men (mean age 32 ± 0.5 years) who were medication-free for at least 3 months. Following audiovisual sexual stimulation, investigators assessed seminal parameters via semen analysis, erectile hemodynamics via colour-Duplex ultrasound Resistive Index, and post-ejaculatory refractory time under continuous erotic stimulation.
What was found
Sildenafil caused no significant changes in seminal parameters or colour-Duplex ultrasound erectile metrics compared with placebo (specific numerical values for these parameters are not reported in the abstract). Sildenafil administration significantly reduced the post-ejaculatory refractory time to 2.6 ± 0.7 minutes compared to 10.8 ± 0.9 minutes for placebo (P < 0.0001).
Why it matters
This indicates that single-dose sildenafil does not impair sperm characteristics in fertile men and markedly accelerates the resumption of erections after ejaculation in the presence of continuous sexual stimulation.
Limits
The sample was small (n = 20) and restricted to young, healthy, fertile volunteers, limiting generalizability to infertile men or those with erectile dysfunction. The trial examined only acute single-dose administration rather than chronic use, and numerical values for semen parameters and ultrasound indices were not reported in the abstract.
Cited by
- supports The male post-ejaculatory refractory period ranges from minutes in younger men up to approximately 36 hours (a day and a half) in older men.