Selecting an apparatus and its associated experimental conditions for testing

There are four apparatuses which are generally recognised by pharmacopeias (e.g. USP) and other regulatory bodies which may be used for drug dissolution testing for product evaluation. However, choosing one of these apparatuses, or any other, is difficult as there are no appropriate scientific or rationale criteria available for such selections. 

All four apparatuses usually provide different results for the same product and choice is left to the analyst to select one which meets the expected behaviour of the product. This approach has two flaws: (1) certainly, these apparatuses are not measuring the same property (dissolution), otherwise, results would have been the same. A product cannot have four or more values for the same parameter; (2) a product, or its property, cannot be evaluated using itself as a reference to select a technique (apparatus).

Therefore, it appears that current practice of product dependent choices of dissolution apparatuses, and its associated experimental conditions, is not a valid practice. Thus, results obtained in such manners to reflect true dissolution characteristics of the product whether test is for QC or IVIVC purpose or any other, may not be valid as well.  

Before selecting an apparatus, one has to establish its relevancy by conducting a dissolution test with a reference product of known and accepted drug dissolution characteristics. This reference may be from a third party or in-house product, but not the test product, and must have known and acceptable drug dissolution characteristics. Then to establish the dissolution properties of the test product, the apparatus with its associated experimental conditions be used without any changes.

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