Effect of caffeine on increasing the motility of frozen human sperm.

A preliminary report on the effect of the addition of caffeine to 45 frozen sperm samples, in order to restore the effectiveness and motility of frozen stored human sperm, is presented. The addition of 7.2 mM caffeine proved optimal and resulted in 40% to 80% increased sperm motility after 30 days of frozen storage. The use of rapid-rate freezing to produce frozen sperm pellets and the addition of one frozen pellet of buffered caffeine (7.2 mM) to five sperm pellets before thawing are recommonded. For slow-rate freezing in paillettes, the addition of a caffeine solution (final concentration, 7.2 mM) to the sperm and protective medium is recommended. With these methods, frozen storage of hypomotile sperm, which previously could not be preserved by freezing, is now practical.