KINETIC NONEQUILIBRIUM DIALYSIS: STUDY OF MACROMOLECULE INTERACTIONS WITH THIORIDAZINE, MESORIDAZINE AND SALICYLATE

Several physiochemical interactions influence the amount of therapeutic agents which ultimately reaches the pharmacodynamic receptor. Therapeutic agent (ligand)-macromolecule interactions can occur during the absorption, transportation, pharmacodynamic, biotransformation and elimination phases. Methods developed to characterize these interactions usually involve varying the ligand concentration in each set of experimental apparatus to derive the binding parameters. Gustafson developed a newer approach to determine ligand interactions with macromolecules. His technique utilized a dialysis cell in which two streams could flow through by means of a pump. One stream containing ligand and macromolecule was referred to as the donor and the other stream which contained buffer was referred to as the recipient. Each cycle of the two streams through the dialyzer represented a new interaction condition and thus eliminate the necessity of additional apparatus for subsequent binding concentrations. This technique is known as Kinetic Non Equilibrium Dialysis.;The same methodology applied to the study of the association of thioridazine and mesoridazine with human and bovine serum albumins, human globulin, whole human plasma and washed human erythrocytes, established unequivocally that these ligands do not measureably interact with either the soluble macromolecules or the formed elements studied in therapeutic and physiologic concentration ranges.;The utility of the Kinetic Non Equilibrium method in studying ligand-macromolecule interactions has been confirmed using studies of salicylate association with human serum albumin in which previously reported values of the number of binding sites (n) and of the association constant (K) have been found. These values were derived using three different mathematical treatments: Klotz, Scatchard and Thompson-Klotz. There is therefore no doubt that the Kinetic Non Equilibrium dialysis method provides a ready means for estimating n and K values that provides a wealth of data in a relatively short time span while being highly conservative of both macromolecule and ligand.