The objective of this work was to investigate the influence of tablet location along the bottom of a USP apparatus II vessel on polymer erosion and drug release of surface-erodible sustained-release tablets using computational simulation methods. Computational fluid dynamics (CFD) methods were performed to simulate the velocity distribution. A mathematical model was developed to describe polymer erosion and tablet deformation according to the mass transfer coefficient. Numerical analysis was used to simulate drug release controlled by drug diffusion and polymer erosion. The results indicated that tablets located at the off-center position deformed faster than the tablets located at the center position. However, tablet location had no profound impact on drug release rate since all drug release profiles were "similar" according to the f2 similarity values which were above 50. Hence, our simulation supported that the USP apparatus II was a reliable and robust device for the dissolution testing of surface-erodible sustained-release tablets.
Keywords: USP apparatus II; computational fluid dynamics; computational simulation; surface erosion; sustained release; tablet dissolution testing.