Site-specific drug delivery in the gastrointestinal tract.

In recent years there has been a significant increase in available strategies for site-specific delivery in the gastrointestinal tract both to maximize a therapeutic response and to reduce side effects. However, in only a few instances has there been close attention paid to how these products will perform in the heterogeneous environment of the human gut. Targeted oral delivery requires a multidisciplinary approach to research, involving contributions not only from polymer and pharmaceutical scientists but also from experts in gastroenterology and product evaluation. The objective of this article is, therefore, to examine our current understanding of human gastrointestinal physiology and to review the current "state of the art" of available targeting strategies. Emphasis will be placed on human data and, in particular, the interaction between the delivery system and the gastrointestinal tract, as assessed by product visualization studies.