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 design and evaluation of controlled-release systems. The simplest way to control the release of an active agent is to disperse it in an inert polymeric matrix. Controlled-release systems are of interest because they are technologically simple, relatively cheap, and practically unaffected by physiological changes. In this study, a new matrix system was formed by an active principle, metoclopramide hydrochloride, scattered into a biocompatible hydrophobic polymerical mesh, polyamide 12, to achieve sustained and controlled delivery of metoclopramide hydrochloride. This research was conducted to investigate the in vitro drug release behavior from these new inert polymeric matrix tablets. The drug release process was investigated both experimentally and by means of mathematical models. Different models were applied for the evaluation of drug release data. On the basis of our results, a biexponential equation was proposed, Q=Qfast(1)(1 - e(-Kfast t)) + Qslow(2)(1 - e(-Kslow t)), in an attempt to explain the mechanism responsible for the release process. Additionally, the influence of the experimental conditions of the dissolution 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.
Application of binary polymer system in drug release rate modulation. 2. Influence of formulation variables and hydrodynamic conditions on release kinetics.
The significance of factors such as drug solubility, polymer molecular weight, drug loading dose, compression force, and hydrodynamic conditions on drug release from a swellable hydrophilic delivery system was investigated. Hydroxypropyl methylcellulose (HPMC) and pectin were major polymeric constituents of the delivery system. Nifedipine, prednisolone, theophylline anhydrous, and diltiazem hydrochloride with solubilities of < 0.001%, <0.1%, <1%, and >50%, respectively, were used as drug models. Results show that changes in pectin:HPMC ratios, HPMC molecular weight, and hydrodynamic conditions exert notable influences on release rate and release duration from the designed system. In the case of prednisolone, drug loading up to 30% (w/w) of the matrix composition (pectin:HPMC K4M; 3:6) had no effect on zero-order release kinetics, and the delivery system was insensitive to changes in compression force (2000 to 5000 lb). For nifedipine, theophylline, and diltiazem, determination of mean dissolution time (MDT) for 50 and 80% drug release provided accurate information on release behavior. The dominating effect of matrix composition over variations in drug solubilities in controlling drug release from the delivery system was evident from similarities in dissolution profiles. It is further shown that hydrodynamic stress and intensity of fluid flow causes greater attrition at the swollen periphery and is responsible for dramatic increases in release rates. This latter observation confirms that the mechanism of drug release from this swellable system is erosion dependent. Influence of polymer molecular weight and drug solubility on release kinetics and the potential of the delivery system is discussed.
Metallurgical Process Engineering
The "material of choice" - steel.- Uprising of China's steel industry.- Process manufacturing industry and process engineering.- Engineering science in steel manufacturing process.- Analysis and integration of metallurgical manufacturing process.- Multi-dimensional mass flow control for metallurgical manufacturing process.- Time factors in steel manufacturing process.-Operating dynamics in the production process of steel plant.- Structure and mode of steel plant.- Steel plant and environment.