Abstract
ABSTRACTSite specific drug release presents advantages over conventional release, among them the decrease of required doses and side effects, drug protection, maintenance of bioavailability and optimization of pharmacological effects. Colon has been studied as site for drug release for both local and systemic action, since it offers a more amenable environment, with pH values near neutrality, reduced proteolytic activity and longer transit times. Among the various strategies explored to prepare colon specific release systems, the most rational is that using systems degradable by the colonic microflora. In this sense, polysaccharides are been used as excipients in the design of such systems because, additionally to be able to undergo microbial biodegradation, they are widely available and safe. An example for that is starch, widely used in medicines, foods and cosmetics. Resistant starch - RA is obtained by the retrogradation of starch and although resistant against the action of digestive enzymes, can be fermented and disintegrated by the colonic microflora, which makes it a potential candidate for the design of colon specific drug delivery systems. High amylase has been considered the preferred material to prepare products with high RA contents by hydrothermal retrogradation. Pectin is also a polysaccharide resistant to proteases and amylases found in the higher portions of the gastrointestinal tract, but it is also digested by the colonic microflora and widely used as excipient. However, it presents a high aqueous solubility, which can be unfavorable for the control of the drug release. Polymer films represent an important tool in the design of drug delivery systems, mainly because of their ability to cover solid dosage forms and this film forming capacity can be favored or even created by polymer associations. The association of RA and pectin seems to present potential for the preparation of films to be used in colon specific drug delivery systems. Therefore, the aim of this project is to prepare and to analyze such films in relation to their morphological (surface, thickness, mechanical resistance, permeability to water vapor) as well as rheological aspects and to evaluate their potential to be used in colon specific drug delivery systems (swelling, dissolution and digestion properties).
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