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.

Release modelling of nanoencapsulated food ingredients by probabilistic models: Cellular Automata and Monte Carlo Methods

“…The theory on USP II apparatus medium influence was due to Ramtoola and Corrigan (1987) and Healy and Corrigan (1996), who examined the influence of particle size and discovered that, in general, a higher dissolution rate occurs for increased excipient particle size. Consequently, two boundary layers were defined in the apparatus: the concentration layer, where advection governs mass transport and the velocity boundary layer (a small region around the compact), where diffusion is the main mass transport Crane, Hurley, et al, 2004;McMahon et al, 2003). In parallel work , diffusion was modeled as the sum of the set of particles that can move to a new position.…”

“…To calculate diffusion mass transport processes in various models, Fick's second law is used in different forms, depending on the geometry of the polymer device (e.g., Cuppok et al, 2011;Kreye, Siepmann, & Siepmann, 2011;Muschert, Siepmann, Leclercq, Carlin, & Siepmann, 2009;Seidenberger, Siepmann, Bley, Maeder, & Siepmann, 2011). For example, a finite-difference approximation for determining the mass transfer rate, from cylindrical components consisting of multilayers, was applied in McMahon, Crane, Ruskin, and Crane (2003), McMahon, Crane, Ruskin, and Crane (2007), and McMahon (2008. 2.…”