The Mechanics of Drug Dissolution

Abstract

A numerical method for approximating the mass flux from a dissolving cylindrical drug compact, a tablet, is presented. The tablet consists of alternating layers of drug and inert material. The dissolution takes place in a non‐reactive medium using a standard stirring device and is considered to be two dimensional and steady. A finite difference scheme is used to generate an approximation to the concentration boundary layer. By integrating across the velocity* concentration profile at the trailing edge, the mass flux is estimated. This value differs by 0.9% from the recent estimate of Crane et al. who used a Pohlhausen approximation to the concentration boundary layer. The finite difference concentration profile at the trailing edge also agrees very well with the equivalent Lévêque exact solution. We conclude that the finite difference model is behaving as expected.