title: 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.
mesh_terms: D002209:Caprolactam; D003692:Delayed-Action Preparations; D004058:Diffusion; D005030:Ethylenes; D006207:Half-Life; D006854:Hydrocortisone; D008433:Mathematics; D008962:Models, Theoretical; D011108:Polymers; D011739:Pyrimethamine; D012828:Silicones; D013607:Tablets; D013997:Time Factors
chemical_list: D003692:Delayed-Action Preparations; D005030:Ethylenes; D011108:Polymers; D012828:Silicones; D013607:Tablets; D002209:Caprolactam; D006854:Hydrocortisone; D011739:Pyrimethamine