ABSTRACT
Due to the rapid progress of molecular biology and biotechnology over the last decade, peptide-and proteinbased reagents have attained considerable relevance for the diagnosis and therapy of diseases, and this trend is still increasing. For the same reason, there is an emerging interest in novel polysaccharides (e.g. heparinderivatives) and polynucleotides (e.g. antisense agents, gene therapy; Anderson, 1992; Davis, 1992). Clearly, the administration of all these new ‘biopharmaceuticals’ require particular formulations which are governed by the structure, physico-chemical properties, stability, pharmacodynamics and pharmacokinetics of these compounds (Lee, 1991). In particular, the new strategies which may be used for their convenient, safe and effective administration to patients in place of injections (parenteral routes) are presently being investigated with great efforts both in industry and academia. Apart from other so-called ‘alternative routes’—e.g. nasal, trans-dermal, pulmonal, buccal, ocular, vaginal or rectal-the peroral route of drug administration is considered as the most convenient. However, from a technical point of view this route is probably the most difficult. The site of actual drug absorption (intestines) is fairly remote from the site of drug administration (mouth). During gastrointestinal transit, numerous unpredictable obstacles (food, mucus, acid, digestive enzymes) are encountered. Apart from these the problem still remains how can such mostly hydrophillic, large and metabolically sensitive compounds be transported across the biological barrier of the intestinal epithelium in sufficiently large amounts for successful therapeutic effects.
