Establishment of the Flux Dialysis Method for Highly Bound Compounds in Human Plasma and Rat Brain Homogenate

The fraction unbound (f_u) data in plasma and tissue are important to predict drug interaction, develop PK/PD relationships, and estimate therapeutic index. For compounds with high molecular weight, high lipophilicity, and severe non-specific binding, instability in matrix and other complex properties, they are usually highly protein bound and difficult to be determined accurately using standard assays. In this study, the flux dialysis was applied to determine fu in human plasma and rat brain homogenate for commercial compounds with highly bound, instability and other complex properties. The human plasma f_u of 18 compounds and rat brain homogenates f_u of 9 compounds measured in this study correlated well with those reported in the literature (R²>0.98).