In continuation of the earlier post (link), this post describes some of the steps commonly described in the literature as method development but should not be considered method development steps. These steps are usually variations in experimental conditions to achieve certain desired characteristics of a dissolution test such as discriminatory, improved reproducibility and/or bio-relevancy. The variations can be are numerous, such as choice of apparatus (paddle or basket), spindle rpm (50, 75, or 100), media (water or buffer), pH (between 1 and 6), choice of de-aeration, or its technique, use and choice of a sinker, etc.
Considering these steps or practices as method development is incorrect because of two reasons:
1. These practices are commonly used during the product development stage. At this stage, an analyst is working with the variations in the product (formulation and manufacturing attributes), which requires a fixed dissolution method, not variations in the method itself, to evaluate the impact of product variations.
2. The products are developed for human use. The drug is expected to be released from the product in the GI tract environment, which remains constant, from product to product. The in vitro dissolution testing conditions simulate this GI tract environment. Therefore, these conditions should also remain constant.
It is, therefore, critical that a dissolution test method should be decided and fixed, reflecting GI tract environment, prior to working on the development of a product.