(37d) Mathematical Modeling of Drug Release: Analysis of the Effect of Absorption Rate and Finite Dissolution Rate On Rate of Drug Release

Dosage forms with controlled drug release deliver the drug at a prolonged rate by delaying the drug in the GI tract where it is absorbed. As it is know the rate of absorption in the GI tract is dependent on many factors such as the presence of food in stomach, PH in the GI tract etc? depending on these factors the absorption process can either be fast or slow. Though there is a large spectrum of mathematical models and approaches describing drug release controlled by various mechanisms such as diffusion, dissolution, polymer biodegradation etc?there are very few models which take into account the affects of physiological parameters such as the rate of absorption of drug. There are various complex transport and chemical processes which play a role in the drug release from such systems. But the knowledge of these processes is still limited.

Mathematical modeling of controlled drug delivery systems can help us understand the underlying mass transport mechanisms involved in the control of drug release. It also plays an important role in providing us with valuable information such as the amount of drug released during a certain period of time and when the next dosage needs to be administered. Thus potentially reducing the number of in-vitro and in-vivo experiments which in some cases are infeasible.

In this work we propose a mechanistic model for drug release from a spherical polymer matrix system into a compartment of finite volume. The liquid from the compartment enters the polymer matrix, dissolves the drug thus enabling it to release into the medium. Once the drug is released into the compartment it is subsequently absorbed. Diffusion, dissolution and rate of absorption are the 3 mechanisms believed to control the drug release rate are. The proposed model analyses the affects of these mechanism on the rate of drug release. The fraction of drug release is calculated and results are compared with the data from literature and also with Crank's classic diffusion model for drug release from a spherical particle.