Dynamic dialysis in drug-erythrocyte interactions.

Application of dynamic dialysis to drug binding to erythrocytes was found to be more complex than previously described. Drug molecules located intracellularly in erythrocytes must diffuse through erythrocytes membranes before diffusing through the dialysis membrane to the external sink in dynamic dialysis. One must consider drug within the dialysis sack and within the erythrocyte and their corresponding volumes. When binding occurs in these internal compartments, different equations result for computing Dt, the total drug within the dialysis bag. With these equations and theoretically generated data, the results of "double dialysis" on the data produced in dynamic dialysis studies of drug-erythrocyte interactions were examined. The intracellular binding of drug by the erythrocyte to a single class of preexisting noninteracting sites could be misinterpreted as cooperative binding, or binding to at least two classes of sites, when the data of dynamic dialysis are treated in the Scatchard format.