High-Affinity Binding of Ethacrynic Acid Is Mediated by the Two Most Important Drug Binding Sites of Human Serum Albumin

The binding of ethacrynic acid to human serum albumin was investigated by means of circular dichroism and equilibrium dialysis measurements, using native human serum albumin and albumin derivatives with chemical modifications impairing specifically drug binding to the indole and benzodiazepine binding site or the azapropazone-warfarin binding area, respectively. The data presented indicate that the high-affinity binding of ethacrynic acid to human serum albumin is mediated by these two important drug binding sites. Accordingly, even at relatively low concentrations ethacrynic acid displaces other drugs from both binding sites.