Abstract
The binding of salicylic acid to rabbit plasma protein in vitro and in vivo was examined using the semi-microultrafiltration method developed by Imamura et al. This method is suitable for the determination of intact binding of drugs in vivo since the plasma sample need not be diluted and the volume of filtrate is so small that the drug-protein equilibrium may not be affected. The binding parameters of salicylic acid to rabbit serum determined in vitro were : n=1.77 and k=2.53×104M-1, where n and k are the maximal number of binding sites and the binding constant, respectively. The percentages of salicylic acid bound in vivo following oral administration of sodium salicylate to rabbits were in fair agreement with the theoretical values estimated using the binding parameters described above. It appears that the plasma protein binding of salicylic acid in vivo is predictable from data obtained in vitro in rabbits.
