Oral drug release systems based on pectin

Abstract

Pectin is a natural polysaccharide and its specific enzymatic degradability by colonic microbiota makes it a promising material for designing drug release systems, mainly those intended for targeting drugs to the colon. However, in despite of pectin resistance against proteases and amylases, remaining as aggregates of macromolecules in acid medium, a great challenge to optimize the performance of pectin in such systems lies in its high hydrophilicity that, in several times, results in an undesirable premature release of drugs. Blends of pectin with other polysaccharides and cross-linking reactions are valuable tools to modulate such properties of pectin, particularly reducing its solubility. These approaches have been focus of important researches of our research group and our findings have been published in important scientific journals. Blends of pectin and retrograded starch (RS) allowed the preparation of free films with suitable mechanical properties and reduced dissolution of films in acid media, while their high resistance against enzymatic digestion by pancreatin was demonstrated. The same polymer association was exploited for preparing tablets containing sodium diclofenac (SD), and the presence of pectin reduced significantly the drug dissolution in acid medium. In another study with free films, the blends of pectin-high amylose starch (HAS) crosslinked with sodium trimetaphosphate (STMP) contributed to the reduction of their hydrophilicity. This polymer association was also exploited for preparing hydrophilic matrices from which the drug release rates in acid medium were lowered. In addition, this same cross-linked HAS/pectin blend was employed for preparing microparticles loaded with SD by immersion and the mixtures containing the same proportion of polymers allowed a more effective control of drug release rates. Furthermore, microparticles obtained by physical mixture of polymers showed the lower percentage of drug released in acid medium and this behavior was attributed to the pectin that provides a diffusion layer of high viscosity that reduces the drug release rate. The association of pectin with gellan gum for preparing mucoadhesive beads by ionotropic gelation provided a pH dependent dissolution behavior, allowing reduced drug release rates in acid media. The purpose of this review is to evidence the importance of pectin as a carrier in the design of different drug release systems, aiming the targeting of drugs. Besides, the association of pectin with other polysaccharides and the cross-linking reaction are demonstrated to be reliable strategies to modulate the properties of the systems according to specific therapeutic needs.