De-aeration of a medium and vibration free environment – perfect attention deflectors

It is a well-established fact that current dissolution apparatuses (paddle/basket) are flawed and cannot provide relevant and reproducible results. The flaw is because of poor hydrodynamics within a dissolution vessel i.e. product and medium do not interact appropriately and reproducibly resulting in cone formation, tablet/capsule positioning effects etc. Thus, tests provide highly variable and unpredictable results, which have been shown in many reported experimental studies.

Rather than addressing the issue or the flaw, unfortunately focus has been diverted in promoting that the reasons of such unpredictable behaviour are due to lack of control of de-aeration of dissolution medium and presence of vibration in and around the apparatuses.  It is important to note that there is no logical or experimental basis or evidence available in support of such a view. However, there are persistent discussions and promotions of such views.

It may be important to further note that this promoted view of the de-aeration or vibration aspect originated from frequent failures of calibration of apparatuses using USP prednisone tablets. The effect of de-aeration and vibration on actual products for human use is almost non-existent. The use of chemical calibration has already been considered unreliable because of the unpredictability of results or failure of perfectly working dissolution apparatuses. Their use is gradually diminishing, however, “slogans and chanting” of de-aeration and vibration continues.

Therefore, analysts should critically evaluate the promoted views on the topic as these are not scientifically valid claims.

The dissolution tests are conducted to evaluate drug release characteristics of products in the human GI tract, which is neither de-aerated nor vibration free. Therefore, conducting dissolution tests in a de-aerated medium and/or vibrating free environment should be considered as a physiologically irrelevant practice as well.

For appropriate dissolution testing, the medium should be equilibrated with dissolved gases at 37 ºC and stirred gently but thoroughly.

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