Action of pentoxifylline directly on semen

In the presence of pentoxifylline, spermatozoa can be induced to increase certain motion characteristics. This drug capability has been used to study the effect when applied directly on semen. An equal volume of pentoxifylline was added to semen, which was then incubated for 1 h before processing. Sperm motion was assessed employing computer-assisted semen analysis. The results showed that pentoxifylline increased curvilinear velocity, straight line velocity and lateral head displacement, the latter effect being concentration-dependent over the entire range of concentrations tested (r = 0.93, P < 0.0001). With a high concentration of pentoxifylline, spermatozoa exhibited characteristics consistent with hyperactive-like motion. Semen characteristics showed marked interindividual variation, ranging from 0 to > 40% response to 6 mM pentoxifylline challenge. Some 10% of patients showed little or no response to pentoxifylline. The sum of the percentage changes in curvilinear and straight line velocity, lateral head displacement and manual sperm count for each dose group was used to produce the stimulation index, measuring the overall response of spermatozoa to the drug. This stimulation index showed that the most effective concentration was 6 mM pentoxifylline, considerably higher than the 3.6 mM pentoxifylline used commonly for separated spermatozoa.