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 d rug within a swollen polymeric hydrogel matrix plays a determinant rol e in the analysis of the controlled release processes, in the previsio n of their kinetics and in the design and formulation of efficient con trolled release drug delivery systems, In this paper, we applied the s o-called inverse sectioning method to a scleroglucan hydrogel matrix l oaded with theophylline, and illustrated a procedure for a reliable es timation of D-g. This crucial parameter is calculated by correlating t he experimental data with the model resulting from the analytical solu tion of the second Fick law in one dimension, obtained under the appro priate initial and boundary conditions, The quality of the adopted mod el and the uncertainty on the calculated value of D-g are discussed on a statistic basis. (C) 1997 Elsevier Science Ireland Ltd.