In vitro release testing

 

Sometimes, commonly used in vitro dissolution or release tests cannot provide data that are appropriate for the system being studies.

 

For instance, when ophthalmic drops are introduced into the eye, the residence time is only a few minutes. Thus, any in vitro release test must provide experimental data in that timeframe to be relevant to the physiological application, and very rapid sampling is required.

 

Similarly, supersaturating formulations can require both rapid sampling AND characterization of the dissolved free drug concentration, which corresponds to the drug’s absorbable form in vivo.

 

Testing for other formulations might be much slower. For instance, transdermal experiments using traditional Franz cells typically use a stirred liquid receiving medium. However, prolonged exposure of skin to liquid receivers can lead to excess hydration, leakage of skin components, microbial overgrowth, and skin breakdown. PMD has been used with non-solution receiving media that can be adjusted to minimize these problems. Together with our published models, this allows determination of the skin permeability more rapidly than with other in vitro methods.

 

Physical Pharmaceutica has performs testing on the following systems:

  • Ophthalmic emulsions—comparative in vitro release rate tests
  • Supersaturation, spring and parachute effects, and precipitation kinetics
  • Extended transdermal drug permeation experiments that avoid skin breakdown
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