Characterization of the Hydrodynamics in the USP Basket Apparatus Using Computational Fluid Dynamics

Area of Science:

• Pharmaceutical Sciences
• Chemical Engineering
• Computational Science

Background:

• Computational fluid dynamics (CFD) is widely applied to the USP paddle apparatus II but less so to the USP basket apparatus I.
• Previous CFD studies on the basket apparatus have not fully accounted for tablet presence or in vivo conditions.

Purpose of the Study:

• To investigate hydrodynamics within the USP basket apparatus I using CFD, considering tablet placement and fluid properties.
• To compare CFD predictions with in vivo conditions and analyze factors affecting drug dissolution.

Main Methods:

• Developed CFD models for the USP basket apparatus I, incorporating a tablet.
• Simulated various basket speeds and fluid viscosities (0.001 Pa-s and 1 Pa-s).
• Analyzed velocity, surface shear stress, strain rate, and turbulent energy dissipation.

Main Results:

• Tablets near the basket perimeter experienced significantly higher velocities and shear stress (up to 5-fold) than central tablets.
• Higher basket speeds improved velocity prediction at the center but reduced shear stress compared to in vivo.
• High viscosity (1 Pa-s) increased shear stress by 10-fold but decreased strain rate, potentially impacting dissolution.

Conclusions:

• CFD analysis reveals complex, non-uniform hydrodynamics in the USP basket apparatus I.
• Significant discrepancies exist between basket apparatus and in vivo conditions.
• Findings can inform optimization of in vitro dissolution testing for improved in vivo relevance.