In vitro effects of sildenafil and phentolamine, drugs used for erectile dysfunction, on human sperm motility

Objective: The aim of this study was to determine the effects of sildenafil and phentolamine on sperm motility in vitro. Study Design: Semen or washed sperm was mixed with various doses of sildenafil or phentolamine and analyzed for motility during a 30-minute period. The pH was measured for each of the samples tested. Statistical analyses were performed with analysis of variance. Results: A 200-μg/mL dose of sildenafil had no effect on sperm motility. However, the highest dose (2000 μg/mL) significantly reduced motility by about 50%. The pH was reduced in this high-dose sample. The lowest dose of phentolamine (20 μg/mL) had no effect, whereas a dose of 200 μg/mL resulted in a significant reduction in sperm motility. The highest dose (2000 μg/mL) stopped virtually all sperm from moving. Conclusion: This study demonstrated a direct dose-related effect of phentolamine on reducing sperm motility. Only the highest dose of sildenafil had an effect, which may have been caused by a decline in pH. (Am J Obstet Gynecol 2000;182:1093-5.)