Figure 4.

Schematic diagram of semi-physiologically based pharmacokinetic model (PBPK) model describing the pharmacokinetics of verapamil and furosemide in rats. A_i, Q_i and V_i indicate drug amount, blood flow and volume in corresponding compartment, respectively. k_i, k_a,i and k_b,i represent the transit rate constant, drug absorption rate constant and efflux rate constant from enterocytes to the gut lumen, respectively. Cl_int,gwi, Cl_int,liver and Cl_int,kidney mean the intrinsic clearance in enterocytes, hepatocytes and kidney, respectively.