ABSTRACT
The colon, by virtue of favorable pH and reduced motility, is home to a dense population ofmicro-organisms [over 400 species (1), numbering 1011-1012 colony forming units per ml of colonic material (2)]. The presence of a resident microflora is a highly specific environmental feature of the colon, contrasting markedly with the sparsely populated upper gastrointestinal tract; this difference can be exploited in order to effect site-specific drug release in the colon (3). The consistently high levels of bacteria in the colon mean that it is much more reliable than the more variable pH (4) or transit time (5) which have been investigated for colonic delivery. Prodrugs, e.g., sulfasalazine, which rely on the action of colonic bacteria to break down an inactive precursor and release the active drug moiety (mesalazine or 5-aminosalicylic acid), have been in use for many years, but are highly drug specific, and there is a need for the development of a more universal system which can be adapted to a variety of drugs for both local and systemic treatment. An amylose based, bacterially triggered system has been developed to fulfil this need.
