In vitro release of metoclopramide from hydrophobic matrix tablets. Influence of hydrodynamic conditions on kinetic release parameters

There has been growing interest in the subject of drug delivery and the des ign and evaluation of controlled-release systems. The simplest way to contr ol the release of an active agent is to disperse it in an inert polymeric m atrix. Controlled-release systems are of interest because they are technolo gically simple, relatively cheap, and practically unaffected by physiologic al changes. In this study, a new matrix system was formed by an active prin ciple, metoclopramide hydrochloride, scattered into a biocompatible hydroph obic polymerical mesh, polyamide 12, to achieve sustained and controlled de livery of metoclopramide hydrochloride. This research was conducted to inve stigate the in vitro drug release behavior from these new inert polymeric m atrix tablets. The drug release process was investigated both experimentall y and by means of mathematical models. Different models were applied for th e evaluation of drug release data. On the basis of our results, a biexponen tial equation was proposed, Q=Q(fast)(1)(1-e(-Kfastt))+Q(slow)(2)(1-e(-Kslo wt)) in an attempt to explain the mechanism responsible for the release pro cess. Additionally, the influence of the experimental conditions of the dis solution devices, such as rate of flow and pH of dissolution medium, on the parameters that characterize the release mechanism was studied, and it was found that the main factor was the hydrodynamic condition of rate of flow.