A PRACTICAL APPROACH TO EVALUATE THE EFFECT OF THE AQUEOUS STAGNANT LAYER ON DRUG RELEASE FROM POLYMERIC DEVICES

The present study describes an approach to characterize drug release f rom a sustained drug delivery system composed of the natural fibrin po lymer. The biochemical reaction between fibrinogen and thrombin has be en used to produce potentially natural, biodegradable, biocompatible, sustained drug delivery systems. One of these is a promising implantab le sheet containing entrapped drug. A model was used which described t he release of drug entrapped within a fibrin matrix in which data were treated assuming that flux follows a model consistent with movement t hrough two barriers in series: diffusion in the matrix (path length va rying with time) and diffusion through an aqueous stagnant layer. The experimental design permitted the measurement of rate of transport as a function of time. The methodology made it possible to determine the contribution of each barrier to the overall transport from a single ex periment. This represents a practical approach to evaluate and compare sustained drug delivery systems and demonstrates the need to account for the involvement of barriers that are highly dependent on the way d ata are collected, since they can impact the conclusions that are made relative to the matrix affects.