Often a reason is provided, in the literature, that it is a test to differentiate drug release characteristics of a product reflecting the potential impact of formulation and/or manufacturing differences. This type of test usually does not link or associate with the products’ in vivo drug release characteristics. Such tests are often referred to as “discriminatory tests.” The underlying reason for such a “discriminatory test” is that if the test relates dissolution differences to formulation/manufacturing differences, then the test will flag potential deviation from the expected behavior of the product in vivo (humans). The main assumption here is that the differences in formulation and/or manufacturing attributes would result in vivo drug release characteristics, producing a substandard product. This, unfortunately, is an incorrect assumption because the differences in formulation and/or manufacturing, on their own, do not necessarily result in differences in vivo drug release, at least not in most cases. If this assumption had been correct, then generic products and the industry would not have existed. The reason being, the generic products, which are based on vastly different formulation and manufacturing attributes, but are required to provide the same drug release characteristics in vivo (humans). In addition, the generic products are also required to provide similar dissolution characteristics, thus forms the basis of pharmacopeial (USP) testing.
Therefore, developing or conducting an in vitro dissolution test just to evaluate/assess differences in formulation/manufacturing, without its link to in vivo, is of limited value or use and may be an incorrect practice.