Simulation of the USP drug delivery problem using CFD: experimental, numerical and mathematical aspects

The numerical simulation of the dissolution of drug-containing compacts in a stirred reactive medium is presented. This is of interest to the design of drug delivery systems in which the goal is to design compacts which release the drug according to certain desired release profiles. A moving boundary finite element approach is adopted to simulate dissolution of layered compacts made up of a number of layers of different acids which dissolve at different rates. The simulation results are compared to experimental measurements. Although a number of idealisations have been adopted in the numerical model, good agreement with experiment is achieved. A semi-analytic solution is also developed which leads to an expression for the mass flux from a dissolving cylinder. Results for this model are compared with the numerical and experimental data.