Evolution of the biopharmaceutics classification system (BCS) to oral modified release (MR) formulations; what do we need to consider?

The Biopharmaceutics Classification System (BCS) has provided a mechanistic framework for understanding the concept of drug absorption in terms of permeability and solubility. Regulatory guidance for Immediate Release (IR) products incorporating the BCS has appeared over recent months. Extrapolation of the approach to oral Modified Release (MR) formulations is therefore inevitable, however, further evolution of our thinking is first required. MR products can deliver drug throughout the gastrointestinal tract and it is important that we recognise there is significant heterogeneity in permeability, lumenal pH/contents and gut wall metabolism from stomach to colon.