Dissolution of pharmaceutical tablets: The influence of penetration and drainage of interstitial fluids

In the aim of controlling the different processes involved in the dissolution of pharmaceutical drugs in tablet form, this work proposes integrating a hydro-textural approach to European Pharmacopea standard dissolution. The apparent kinetics in tablet dissolution are produced by several linked phenomena of mass transfer, fluid phase filtration and volume variations. Evidence of a slow liquid penetration phenomenon leads to question about the relative rates of the different dissolution processes, after the surfaces have been wetted, to determine the limiting kinetics in the dissolution of a single component theophylline tablet. A comparison of the overall dissolution rates between an initially dry tablet with the same tablet initially saturated with liquid shows, in this experimental case, that overall dissolution is controlled by diffusion through the outer layer. This study points to the possibility of changing dissolution kinetics by acting on the porosity of the tablet and its greater or lesser capacity to drain the entrapped air. (c) 2007 Elsevier B.V. All rights reserved.