Uptake of acetazolamide by human erythrocytes in vitro

The binding of acetazolamide to human erythrocytes was studied in vitro. Blood and plasma samples were analyzed by electron-capture GLC. At 37 degrees, drug equilibrated between plasma and erythrocytes in approximately 40 min. The effect of plasma concentration on the steady-state level of drug within the erythrocytes was examined. Erythrocyte accumulation of acetazolamide appeared to be a composite of two processes: a nonlinear, saturable process and a linear, diffusion-controlled process. By appropriate linear transformation of the data, estimates of the data, estimates of the erythrocyte binding capacity and the dissociation constant for the drug were obtained.