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Hydrodynamic investigation of USP dissolution test apparatus II
Ge Bai1, Piero M Armenante, Russell V Plank
1Department of Chemical Engineering, New Jersey Institute of Technology, Otto H. York Newark, 323 M. L. King Boulevard, Newark, New Jersey 07102-1982, USA.
Journal of Pharmaceutical Sciences
|June 19, 2007
Summary
Dissolution testing using USP Apparatus II shows significant variability due to unpredictable tablet location. Understanding the hydrodynamics, specifically low velocities and changing gradients near the vessel bottom, is key to improving test accuracy.
Area of Science:
- Pharmaceutical Science
- Fluid Dynamics
- Biomedical Engineering
Background:
- The United States Pharmacopeia (USP) Apparatus II is standard for pharmaceutical dissolution testing.
- Current dissolution testing methods are prone to errors and failures, with limited understanding of apparatus hydrodynamics.
- Variability in dissolution testing can impact drug product quality and regulatory compliance.
Purpose of the Study:
- To experimentally map and computationally predict fluid velocity distribution within the USP Apparatus II.
- To investigate the hydrodynamics in the critical region near the vessel bottom where tablets dissolve.
- To identify factors contributing to variability in dissolution testing.
Main Methods:
- Employed laser-Doppler velocimetry (LDV) for experimental velocity mapping.
- Utilized computational fluid dynamics (CFD) for predictive modeling of fluid flow.
- Simulated standard operating conditions mandated by the dissolution test procedure.
Main Results:
- Flow is dominated by tangential velocity; secondary flows include upper and lower recirculation loops.
- A low recirculation zone exists at the hemispherical vessel bottom, where tablet dissolution occurs.
- Minimal radial and axial velocities were observed just below the impeller, with significant local variations.
Conclusions:
- Small variations in tablet position at the vessel bottom can cause significant changes in local velocities and gradients.
- These hydrodynamic variations are a likely source of the observed variability in dissolution testing.
- Further research into controlling tablet placement or understanding hydrodynamic effects is needed to enhance test reliability.
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