The importance of boundary conditions in the simulation of dissolution in the USP dissolution apparatus

As shown in previous papers, mathematical simulation can be useful in the design of drug delivery systems. We present a finite-difference approximation to the drug mass transfer rate from dissolving cylindrical drug-containing compacts, consisting of alternating layers of drug and inert material. Results are compared with a recent analytical solution to the same problem and with experiment. The two theoretical estimates differ by about 10%, a result of different implementations of a derivative surface boundary condition. The finite-difference model is more physically realistic but the analytical solution is usefully accurate.