“Modeling of Dissolution-Diffusion Controlled Drug Release from Polymeric Systems”.

M.I. CABRERA, J.A. LUNA, R.J.A. GRAU

Rio de Janeiro (Brazil)

Congreso; · 2nd Mercosur Congress on Chemical Engineering. 4th Mercosur Congress on Process Systems Enginering.; 2005

ENPROMER 2005

 Abstract. A new mathematical model of simultaneous dissolution and diffusion controlled drug release from matrix systems is presented. For drug loaded below its solubility, the model assumes discrete distributions of the drug crystals into the saturated polymeric phase. The amount of drug introduced into the polymer matrix beyond the saturation limit is assumed to be present in the form of point mass sources. This approximation avoids to solve a moving boundary problem and renders the mathematical description more tractable compared to consideration of two phases separately. An approach for solving the unsteady-state mass balance equations with point mass sources and general boundary conditions is presented. The design equations are satisfactorily treated transforming the partial differential equation problem into a system of integral equations, which is numerically solved by a simple iterative scheme using successive approximations. The performance of the computational method is analysed covering a wide range of conditions having practical importance. The effectiveness of the proposed approach to examine the effects of the space and size distributions of solid drug particles on the release rate of drug under dissolution-diffusion controlled regime is examined. The method is readily extendible to study polymeric matrix systems with cylindrical and spherical geometries, and it is useful to model release devices used in pharmaceutical, agricultural, environmental, and household applications.