Intestinal Absorption Kinetics Using a Laminar Flow Model

Abstract

The drug concentration profile at non-steady state in the intestine was simulated using a laminar flow model. The transport equation with cylindrical coordinates was solved by a finite difference method to simulate the concentration profile in the tube and the exit cup-mixing concentration. A drug with a various wall permeability coefficient (Pw = zero or 10−5 to 10−3 cm/s) and diffusion constant (D = 10−6 to 10−4 cm2/s) was assumed to be introduced into the tube in a pulse form. The spatial intervals of the grid and the time step were varied to yield the optimum condition for calculation. The concentration profile in the tube as the time elapsing and the exit cup-mixing concentration versus time profile were shown graphically. Pw and D influenced the concentration profiles. This suggests the possibility of the estimation of Pw and D by determining the exit cup-mixing concentration after a pulse input to a perfused intestine under a laminar flow condition. © 1989, The Pharmaceutical Society of Japan. All rights reserved.