Abstract
The binding of salicylic acid to human serum protein was examined in vitro and in vivo using the semi-microultrafiltration method. The binding parameters of salicylic acid to human serum determined in vitro were : n=2.14 and k=2.05×104M-1. The percentages of salicylic acid bound in vivo (96.5-97.1%) following oral administration of 9.3 mg/kg of sodium salicylate to normal subjects were in good agreement with the theoretical values estimated using the binding parameters described above. Furthermore, a good linear relationship between saliva and serum concentrations of salicylic acid was observed in the low range of serum concentration (-64.6 μg/ml). A theoretical approach, however, indicates that the saliva-serum concentration ratio of salicylate becomes markedly higher with increasing concentration in the serum. It is suggested that the serum protein binding of salicylic acid, which has a high binding affinity and a wide range of therapeutic concentration, must have significant effects on its distribution into the extra-vascular fraction, including secretion into the saliva.
