Simulating the hydrodynamic conditions in the United States Pharmacopeia paddle dissolution apparatus |
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Authors: | McCarthy Leonard G Kosiol Carolin Healy Anne Marie Bradley Geoff Sexton James C Corrigan Owen I |
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Institution: | (1) Department of Pharmaceutics and Pharmaceutical Technology, Trinity College Dublin, Ireland;(2) Department of Mathematics and Trinity Centre for High Performance Computing, Trinity College Dublin, Ireland |
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Abstract: | The objective of this work was to examine the feasibility of developing a high-performance computing software system to simulate
the United States Pharmacopeia (USP) dissolution apparatus 2 (paddle apparatus) and thus aid in characterizing the fluid hydrodynamics
in the method. The USP apparatus was modeled using the hydrodynamic package Fluent. The Gambit program was used to create
a “wireframe” of the apparatus and generate the 3-dimensional grids for the computational fluid dynamics solver. The Fluent
solver was run on an IBM RS/6000 SP distributed memory parallel processor system, using 8 processors. Configurations with
and without a tablet present were developed and examined. Simulations for a liquid-filled vessel at a paddle speed of 50 rpm
were generated. Large variations in fluid velocity magnitudes with position in the vessel were evident. Fluid velocity predictions
were in good agreement with those previously published, using laser Doppler velocity measurements. A low-velocity domain was
evident directly below the center of the rotating paddle. The model was extended to simulate the impact of the presence of
a cylindrical tablet in the base of the dissolution vessel. The presence of the tablet complicated the local fluid flow, and
large fluid shear rates were evident at the base of the compact. Fluid shear rates varied depending on the tablet surface
and the location on the surface and were consistent with the reported asymmetrical dissolution of model tablets. The approach
has the potential to explain the variable dissolution results reported and to aid in the design/prediction of optimal dissolution
conditions for in vitro-in vivo correlations. |
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Keywords: | computational fluid dynamics (CFD) USP paddle apparatus dissolution hydrodynamics modeling |
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