Hydrodynamics-induced variability in the USP apparatus II dissolution test

Jennifer L. Baxter, Joseph Kukura, Fernando J. Muzzio

Research output: Contribution to journalArticlepeer-review

105 Scopus citations


The USP tablet dissolution test is an analytical tool used for the verification of drug release processes and formulation selection within the pharmaceutical industry. Given the strong impact of this test, it is surprising that operating conditions and testing devices have been selected empirically. In fact, the flow phenomena in the USP test have received little attention in the past. An examination of the hydrodynamics in the USP apparatus II shows that the device is highly vulnerable to mixing problems that can affect testing performance and consistency. Experimental and computational techniques reveal that the flow field within the device is not uniform, and dissolution results can vary dramatically with the position of the tablet within the vessel. Specifically, computations predict sharp variations in the shear along the bottom of the vessel where the tablet is most likely to settle. Experiments in which the tablet location was carefully controlled reveal that the variation of shear within the testing device can affect the measured dissolution rate.

Original languageEnglish (US)
Pages (from-to)17-28
Number of pages12
JournalInternational Journal of Pharmaceutics
Issue number1-2
StatePublished - Mar 23 2005

All Science Journal Classification (ASJC) codes

  • Pharmaceutical Science


  • Computational fluid dynamics
  • Dissolution testing
  • Hydrodynamics
  • Shear
  • USP apparatus II


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