A unified mathematical model for diffusion from drug–polymer composite tablets

Abstract

The derivation and experimental verification of a unified mathematical model for the estimation of drug release rate from drug-polymer composite tablets are presented. Cylindrical coordinates are utilized in the solution of the diffusion equation for a three-dimensional system. The model is applicable to tablets that range from the shape of a flat disk (radius greater than thickness) to that of a cylindrical rod (radius less than thickness). The general solution for the fraction of drug released at a time t is (see article). This approach to a three-dimensional system, utilizing cylindrical coordinates, presents a comprehensive method for the estimation of drug release rates from sustained release tablets with drug distributed homogeneously throughout a polymer matrix. The calculated and experimental drug diffusion rate of pyrimethamine from pyrimethamine-silicone rubber composite tablets that range in shape from that of a disk to a cylinder, and of hydrocortisone from EVA, polycaprolactone, and PVA terpolymer, are compared.

Modelling drug release from inert matrix systems: From moving-boundary to continuous-field descriptions

“…Such an analysis has been performed by Fu et al (1976) when no solubility limitations exist (A 0 < C s ). However, when there is an excess of drug (A 0 > C s ), the analytical treatment becomes considerably more involved.…”

Quantifying diffusion-controlled drug release from spherical devices using Monte Carlo simulations

“…Solutions of Fick's second law can provide analytical relations for diffusion-controlled release curves obtained from devices of simple geometries [3,4], like slabs, spheres, or cylinders. Even though analytical results directly demonstrate the dependence of release characteristics on the parameters of the system, such solutions are not available when release mechanisms other than diffusion are significant, or when interparticle interactions are present.…”

Comparison of the structure and the transport properties of low-set and high-set curdlan hydrogels

“…The amount of release material could be described as a function of time using the relation expressed by Eq. (5), derived by Fu et al [35] M t M 1 ¼ 1 À …”