“Developing IVIVC” and establishing drug concentration-time (C-t) profiles

The terminology of “developing IVIVC” is often used in the area of drug dissolution testing which reflects developing a relationship between in vitro (dissolution) and in vivo (bioavailability) results.  However, in reality, the statement and view appear redundant, as this relationship always exists between in vitro and in vivo results. In fact, existence of this relationship (IVIVC) forms the basis of dissolution testing practice. 

So, then the question is, why are these IVIVC development studies frequently conducted and described in the literature? The reason may be explained as follows:
 
The apparatuses commonly used for dissolution testing, in particular paddle and basket, do not provide relevant dissolution results as they do not appropriately simulate an in vivo environment. So, instead of using apparatuses which would appropriately simulate an in vivo environment, studies are conducted to find or to “develop” experimental conditions to obtain in vitro results which would match the in vivo results. Thus this practice of developing product specific experimental conditions (apparatus, medium, rpm etc) has become known as “developing IVIVC”. This practice of IVIVC does not serve any useful purpose for predicting in vivo results, relating in vitro results to in vivo outcome or assessing drug release characteristics of the product.

Having said that, question then becomes, what is the intended purpose of IVIVC development?  The purpose is not to develop IVIVC, as stated above this relationship always exist, but determining/predicting the drug concentrations in blood utilizing the IVIVC concept. Thus, the practices of IVIVC and dissolution testing are in fact for establishing (calculating/predicting) drug concentration-time (C-t) profiles in humans. For a more detailed discussion on this subject alongwith description of a simple method for determining C-t profiles,  please see the article (The Open Drug Delivery Journal, 2010, 4, 38-47. (Link).
 
It is very important that one keeps this understanding in mind, otherwise conducting a dissolution test and the results obtained from the testing would be of limited or no value.

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