Are people using drug dissolution testing for product development? Not really!

Title of the post is a bit catchy, but is factually 100% correct, i.e. no one is using dissolution testing for product development, as explained below:

Suppose a formulator would like to develop a product having a certain dissolution characteristic/profile. The product is to be developed for human use; therefore, the target dissolution characteristic/profile should be relevant to humans as well. With this objective in mind, the formulator proceeds to developing a product by mixing some ingredients/excipients and compressing it into tablets, referred to as product “A”. However, the formulator realizes that perhaps all he/she is required to do is to compress the pure drug (powder) into tablets which might give the desired dissolution characteristic. So, he/she compresses the drug powder into tablets as well, referred to as product “B”. Now the formulator would like to determine/compare dissolution characteristics of these tablets, i.e. if they are able to provide the desirable characteristics or require some adjustments. For this purpose, the formulator requires a dissolution test/method (apparatus and associated experimental conditions). Unfortunately, currently no such test/method exists. Therefore, a formulator cannot determine dissolution characteristics of the products, and thus cannot develop a product having a desired characteristic.

On the other hand, what people are doing is that they assume certain dissolution characteristics of the test products and try different experimental conditions such as apparatus, rpm, and medium, to achieve their perceived characteristics. This practice of seeking the experimental conditions is called dissolution method development exercise. What this means is that formulators are “developing” so called dissolution methods, but not using dissolution testing for developing products. This is a serious flaw in the current practices and an example of unfortunate mindset. It is exactly like a situation where someone requires weighing a certain item, and rather than using a weighing balance he/she starts developing the balance using the item of which the weight is to be determined.

In reality, as stated above, what one requires is a validated dissolution method, just like a validated/calibrated balance, to be used during the product development exercises. Fortunately, if one considers the basic underlying science of drug dissolution testing (e.g. see here), then drug dissolution tests become very simple to conduct with a single set of experimental conditions. For example, most, if not all, products can be evaluated using a vessel-base apparatus with crescent-shape spindle set at 25 rpm containing 900 mL water as medium (with or without a small amount to a solubilizer). Such a method can easily be used at the product development stage. The results obtained should be considered as dissolution characteristics of the product. If the results are not as desired or anticipated then the formulator should work with the product to change the product/formulation attributes to obtain desired dissolution profile/characteristic.

A formulator should not consider changing the experimental conditions at will to obtain the desired or expected results, because then there is no point of product development exercise. All one has to do is have any product and obtain any dissolution characteristics one wishes to have by adjusting the dissolution testing conditions.

In short, at present, formulators/analysts are not using dissolution testing to develop products, but spending time in developing dissolution methods which should not be part of the product development exercise.

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