In my opinion, current practices of method development have not only caused the biggest confusion in the industry but also hindered in an appropriate evaluation of drug products using dissolution (release) testing itself.
Current practices of method development suggest that an analyst is to “fish” (seek) experimental conditions, such as choice of an apparatus (paddle/basket), rpm, buffer, pH to establish UNKNOWN dissolution characteristics of a product. Normally, it is suggested that an analyst should have a number of formulations with presumed dissolution characteristics and the analyst should seek experimental conditions which would reflect his/her “presumed” product characteristics. Such practices are often also referred to as developing “discriminating” and/or “lot-to-lot consistency check” methods.
Similarly, the above mentioned practice of “fishing” (seeking) experimental conditions will be considered as developing a bio-relevant method if the analyst tries to match dissolution results with in vivo results (bioavailability/bioequivalence).
Therefore, in practice, an analyst would never know the true product dissolution characteristics but would select experimental conditions which would fit his/her expectations. It is therefore, critical to understand that as it stands now, an analyst or a product developer will never know the true dissolution characteristics of its product. Each and every analyst/product developer is occupied with “developing” dissolution methods which in reality should not be their assignment. Their objective is to develop a product based on its dissolution characteristics, using a standardized and well accepted dissolution method. This is similar to an analogy in which each and every laboratory would be busy in developing their own thermometers and weighing balances to be used for monitoring temperatures and weighing substances, respectively.
It is therefore, essential to note that the pharmaceutical industry requires a standard dissolution tester along with its associated experimental conditions capable of providing dissolution characteristics of pharmaceutical products. The crescent-shape spindle has been developed with these thoughts in mind, which appears to offer a powerful solution to the current confusion and avoids the unnecessary practices of method development.
