Objective: To evaluate the acute effect of sildenafil and tadalafil on seminal parameters in young, infertile patients.
Design: Prospective, randomized, double-blind, crossover clinical investigation on semen parameters after the
administration of a single dose of sildenafil (50 mg) or tadalafil (20 mg).
Setting: An academic hospital as well as a male infertility center and clinical andrology laboratories.
Patient(s): Eighteen young, infertile men.
Intervention(s): Oral administration of a single dose of sildenafil (50 mg) or tadalafil (20 mg) in a blind, randomized
order. The semen samples were collected 1 or 2 hours after each treatment.
Main Outcome Measure(s): Changes in sperm parameters after sildenafil and tadalafil administration, compared
with the basal conditions.
Result(s): A significant increase in sperm progressive motility (median value, 37.0% vs. 28.5%) was observed after
sildenafil administration as compared with baseline; in contrast, a significant decreased value was observed after
tadalafil (median value, 21.5% vs. 28.5%).
Conclusion(s): These preliminary results indicate that sperm motility appears to be acutely affected in young,
infertile patients by a single dose of sildenafil and tadalafil, with opposite effects: stimulatory by the former and
inhibitory by the latter. (
