Sex differences in the pharmacokinetics of salicylates.

The kinetics of disposition of total and free salicylic acid (SA) in blood plasma was evaluated after single and multiple oral administration of acetylsalicylic acid (ASA) to healthy female and male volunteers. In both single and multiple dose studies significant sex differences were found in the plasma levels of SA, which were due, at least in part, to individual, sex-determined differences in the rate of absorption and elimination of SA; a slower absorption rate in men reduced the magnitude of the peak plasma levels of SA. The corresponding area under concentration-time curves were always significantly lower. The elimination rate of SA in men was increased in comparison with women. The higher plasma clearance in men resulted from the kinetics of absorption and elimination. The sex differences appear to be clinical significance, since men achieved lower plasma levels of SA than women after the same weight-adjusted dose of ASA.