Targeting of drugs and delivery systems to specific sites in the gastrointestinal tract.

Particle uptake and translocation occur at specific sites in the gastrointestinal tract. Several drugs are also absorbed from solution only through narrow "windows' in the small intestine. In these circumstances, optimum therapeutic benefit would be obtained if the active agent was targeted to the appropriate site in the gastrointestinal tract. Targeting relies on exploiting a unique feature of the intended site and protecting the active agent until it reaches that site. This minireview highlights the problems in achieving site specificity in the gastrointestinal tract and examines possible solutions to the problem for 2 regions, the stomach and the colon.