Determination of the drug diffusion coefficient in swollen hydrogel polymeric matrices by means of the inverse sectioning method

The accurate knowledge of the diffusion coefficient D-g of an active drug within a swollen polymeric hydrogel matrix plays a determinant role in the analysis of the controlled release processes, in the prevision of their kinetics and in the design and formulation of efficient controlled release drug delivery systems, In this paper, we applied the so-called inverse sectioning method to a scleroglucan hydrogel matrix loaded with theophylline, and illustrated a procedure for a reliable estimation of D-g. This crucial parameter is calculated by correlating the experimental data with the model resulting from the analytical solution of the second Fick law in one dimension, obtained under the appropriate initial and boundary conditions, The quality of the adopted model and the uncertainty on the calculated value of D-g are discussed on a statistic basis. (C) 1997 Elsevier Science Ireland Ltd.