Variability of human sperm response to immediate and prolonged exposure to pentoxifylline

Pentoxifylline improves some motility characteristics of human spermatozoa, but the variability of response to this drug has not been clearly defined. We used computer-assisted sperm motion analysis to examine the in-vitro response of spermatozoa to pentoxifylline. Individuals (n = 31) with normal sperm counts were randomly selected and their spermatozoa exposed to different concentrations of pentoxifylline. Further tests on a subgroup of individuals examined the longevity of spermatozoa in response to this agent. Straight line velocity (VSL) was only improved at 0.1 mM and the major effect of the drug was on curvilinear velocity (VCL) and lateral head displacement (ALH). Prolonged exposure to pentoxifylline enhanced sperm motion only at 0.1 mM. Higher concentrations produced dose-dependent detrimental effects on all the motion characteristics. There was considerable inter-individual variability in both VCL and ALH response ranging from little or no detectable response to a 40% increase above control value. The maximum response was most commonly seen at a concentration of 2 mM pentoxifylline.