Sex differences in absorption kinetics of sodium salicylate

Sodium salicylate in aqueous solution (9 mg/kg) was given by oral and intravenous routes to normal male and female subjects. Because the bioavailability of salicylate was complete, salicylate was given orally in all subsequent experiments. There were sex differences in time required to attain peak salicylate concentration (tmax), but not in maximum plasma salicylate concentration (Cmax). There were no sex differences in apparent volume of distribution, plasma salicylate clearance, or area under the concentration-time curve. In female subjects, tmax tended to reach a nadir at the middle of the menstrual cycle, when gastric emptying time is shortest, whereas Cmax remained relatively unchanged throughout the menstrual cycle. Equilibrium dialysis studies on the binding of sodium salicylate and of 14C-racemic warfarin to plasma from 25 normal male and 25 normal female subjects of similar age disclosed no sex differences either in the extent of binding of these drugs or in serum albumin concentration. The possibility of sex differences in rates of gastrointestinal absorption of other drug should be investigated.