In vitro methods to assess drug precipitation.

A novel in-vitro dissolution system based on the principle of flow-through technique has been designed to evaluate the in-vitro release rate of poorly water-soluble compounds. The flow through appa...

Dissolution of poorly water-soluble drugs in biphasic media using USP 4 and fiber optic system

To simulate the hydrodynamics in the flow-through (USP 4) dissolution apparatus and investigate the effects of hydrodynamics on mass transfer in a low velocity pulsing flow Computational fluid dynamics (CFD) was used to simulate the hydrodynamics and mass transfer in pulsing flow Experimental flow visualisation was used to qualitatively confirm simulated hydrodynamic and mass transfer features The experimental dissolution rate at 8 ml min−1 (226 mm flow-through cell) was compared to the experimental dissolution rate in a free convection system Simulations revealed periods of low velocity at all flow rates, evidence of boundary layer separation, and, at higher flow rates, residual fluid motion during zero inlet velocity periods The simulated diffusion boundary layer thickness varied in certain regions over the course of the pulse The experimental dissolution rate in the free convection system was faster than that at 8 ml min−1 in the flow-through apparatus A low velocity pulsing flow running counter to gravity inhibited the experimental dissolution rate compared to that in a free convection system From the CFD simulations generated, simulation of both hydrodynamics and species transfer is recommended to characterise the influence of hydrodynamics on dissolution in a low velocity pulsing flow

Hydrodynamic and Species Transfer Simulations in the USP 4 Dissolution Apparatus: Considerations for Dissolution in a Low Velocity Pulsing Flow

Assessment of oral bioavailability enhancing approaches for SB-247083 using flow-through cell dissolution testing as one of the screens.

Several factors affecting the dissolution performance of various solid dosage forms tested using the flow-through cell method have been evaluated in this study. These factors include the flow rate, the position of tablets in the flow through cell and the glass beads, as well as the physical properties of the dosage forms. The experimental results indicated that the flow rate through the cell greatly affects drug release from disintegrating tablets. Drug release increases with increasing the flow rate of the dissolution medium, as expected. However, the flow rate does not significantly influence drug release from tablets which are not disintegratable, for example, an erodible tablet. The position of the tablets in the flow cell without glass beads is also of importance. Drug release from horizontally positioned tablets is different from vertically positioned tablets in the flow-through cell. It was also observed that the use of glass beads in the flow cell can make the flow pattern more laminar. Th...

Evaluation of the Flow-Through Cell Dissolution Apparatus: Effects of Flow Rate, Glass Beads and Tablet Position on Drug Release from Different Type of Tablets

A Copley™ fraction collector and a Disotest™ flow-through system were coupled to provide an automatic discrete sampling flow-through dissolution system for use both in the “open-loop” and “closed-loop” mode. The system was used to investigate the release characteristics of adinazolam in sustained release formulations using a pH 1.2 simulated gastric fluid (without enzymes) dissolution medium (USP XXI). These experimental formulations are designed to provide relatively slow to rapid drug release. The dissolution effluent was analysed off-line by reverse phase HPLC to determine the adinazolam concentration at programmed timed intervals. The differential dissolution profiles produced when the system is used in the “open-loop” configuration are more discriminating in describing the release characteristics of the formulations according to the relative release rates than the “closed-loop” cumulative profiles. Using the characteristic dissolution time parameter from the Weibull function, a better correla...

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Papers

A Flow-Through Dissolution Approach to In Vivo/In Vitro Correlation of Adinazolam Release from Sustained Release Formulations