A discriminatory test reflects that it is capable of differentiating a bad batch/product from a good one. The question is how should one define bad vs good? In general a good product, in the context of dissolution testing, is a product that should be capable of releasing a drug from the product in the GI tract in an expected and reproducible manner. It is important to note that a drug release, or dissolution, test is linked to product behavior in the GI tract. On the other hand, it is a well-known fact that currently suggested dissolution methods/testers have no link to the product behavior in the GI tract (link). In fact, it is almost impossible to obtain reliable and physiologically relevant dissolution results using currently suggested apparatuses in particular paddle/basket apparatuses, because of the flaws of the testers (link). Therefore, by extension, it is almost impossible to have discriminatory dissolution methods to differentiate a bad product from a good product.
The irrelevancy of current practices of developing discriminatory tests, methods or testers may also be explained in another way with the following analogy. For example, one may ask if anyone has seen a discriminatory thermometer, laboratory balance, pH meter, spectrophotometer, chromatograph etc. The answer is, not really; because all one does, by using a tester/method, is to measure the value of the parameter. The test/method is used only to determine value/result and the scientist/analyst uses this value for interpretation of the characteristics of the product. For example, one never says, requires or develops a discriminatory thermometer, when one monitors the temperature. One uses the thermometer to measure the value (temperature) of the corresponding parameter (body temperature). The thermometer never tells if a person has a fever or not. It only tells the temperature, but a physician interprets it as a fever or any other deviations. So, why does one have discriminatory dissolution methods or testers? It is simply to market the made-up science and flawed testers. Developing of a discriminatory test/method, as practiced or required, has no meaning and serves no useful purpose. One requires a dissolution tester or method to measure dissolution characteristics of a product reflecting its in vivo dissolution characteristics. Once one has such a method, it automatically becomes a discriminatory test. One does not require any extra effort or steps to make it a discriminatory test. The dissolution results thus obtained using such a method/tester would reflect dissolution characteristics of a product and then the analyst/formulator is to decide whether the product is of acceptable quality/characteristics or not.
Note that, in the true sense of the practice or requirement, we never had a dissolution tester/method therefore we cannot determine dissolution characteristics of any product, good or bad, thus we will never be able to differentiate products, using or repeating the current practices.
Perhaps, an even more confusing aspect of current practices is that of promotion of the dissolution (discriminatory) tests without their link of product behaviour in vivo, the so called “QC tests”. In this respect, it is promoted that a discriminatory QC test means that the test is capable of differentiating a “good” vs “bad” product by differentiating formulation/manufacturing differences. This is again an incorrect assumption/view because, as described above, dissolution tests cannot differentiate anything, they will only measure dissolution characteristics of the product. Secondly, if for some reason, a dissolution test is linked to formulation/manufacturing, differences in formulation and manufacturing by themselves do not define a good or bad product. For example, generic products of numerous drugs are available with significant differences in formulation/manufacturing attributes but are of acceptable (good) qualities. Point being that a discriminatory dissolution test even as QC test has no meaning or use as well, so this should be considered as wasteful practice as well.
In short, one requires a simple dissolution method to measure dissolution characteristics of product reflecting its dissolution characteristics in vivo (GI tract). The discriminatory terminology as used in dissolution testing area appears a made-up requirement and/or irrelevant practice, which has no scientific basis and does not serve any useful purpose.
