It is very important to note that the objective of dissolution testing is to estimate/determine potential drug dissolution/release characteristics of a drug from a product using a simulated gastrointestinal (GI) tract environment. The simulated GI tract environment for dissolution testing purposes is commonly represented by a medium such as water or an aqueous buffer (e.g. pH=6) in a container (vessel) maintained at 37 °C with gentle mixing/stirring. If the volume of the medium is not sufficient to completely dissolve the expected amount of drug present in the product, then a small amount of solubilizer (e.g. SLS) may be used. Dissolution results are often expressed as percentage of drug released at a single time (e.g. 30 or 45 minutes) or multiple times to establish a dissolution profile.

A dissolution test is just like any other simple analytical test utilizing an instrument, such as a thermometer, viscometer or pH meter that one uses for measuring temperature, viscosity and pH of a product, respectively. One does not require, or develop, a product specific thermometer, viscometer or pH meter. One just puts the thermometer or electrode into the liquid or pours the liquid into the viscometer to obtain the reading. This reading will reflect the property of the liquid.

A dissolution tester should be used exactly like that, i.e. monitoring/measuring of dissolution/release characteristics of a product (tablet/capsule) by dropping a tablet/capsule into a dissolution vessel containing a standard volume of dissolution medium with a stirrer and a pre-set rpm. The outcome of the test (% dissolved) will reflect the dissolution characteristics of the product.

No matter how one presents the argument, or dissolution results, describing them such as bio- or IVIVC relevant, discriminatory, or for QC use, the tests must be performed using pre-set and product independent experimental conditions. This is similar to the practice of not requiring a discriminatory or bio-relevant and/or liquid dependent thermometers, viscometers or pH meters, because not only will it logically and scientifically be considered meaningless but will never reflects true product’s characteristics. Similarly, one should not ask for and/or try to develop product dependent dissolution testers or methods (Please, click here to read in detail about dissolution testing).

Dissolution testing using the crescent shape spindle has been developed based on these thoughts which provide simple, scientifically valid and product independent testing and evaluation. For further information in this regard please see the following links (1, 2).

It is now generally recognised that the commonly recommended dissolution testers (paddle/basket) do not provide bio-relevant dissolution results. In addition, it is also well recognised that considering the flow dynamic within the vessels, these testers will provide highly variable and unpredictable results, thus would be of limited or of no use for routine testing as well.

Considering the need and importance of dissolution testing for product development and assessment, it is surprising that it is often suggested that in the absence of another “simple” alternative, one must keep using these testers. Such a suggestion is simply a marketing gimmick to promote the continued use of a flawed technique. It is almost like bicycle promoters suggesting that until and unless proper boats or ships are developed, people must keep using bicycles to cross rivers, because it is the only simpler and cheaper mean available and allowed for such transportation purposes.

On the other hand, the reality is that it is well known that it is the stirring and mixing mechanism, and environments within dissolution vessels which are causing the problem and require change or adjustment. In this regard, it has been shown that with a simple alteration, for example replacing paddle/basket spindle with the crescent-shaped spindle, not only are the artefacts of the paddle/basket apparatuses corrected but dissolution testing itself becomes relevant and extremely simple. For example: (1) one will be able to conduct product independent tests as opposed to product dependent tests, which is a scientifically incorrect practice to start with; (2) as the testing becomes product independent, one will avoid requiring method developments thus reducing cost and time; (3) the same set of experimental condition will be used for product development and QC purposes, thus again saving cost and time; (4) from the simplicity aspect, testers maintain the simple configuration and operation of the basket/paddle apparatuses.

Therefore, it is important to note that there is no reason that one should continue using a flawed system and keep generating useless data. A simpler and improved dissolution tester can be developed by simply modifying the currently used paddle/basket apparatuses e.g. by replacing a stirring element in it with another, such as with the crescent shape spindle.

For further discussion please see the following links: 1, 2, 3