Amidated pectin hydrogel beads for colonic drug delivery - An in vitro study

Hydrogel beads of amidated pectins have been prepared by allowing individual droplets of the pectin solution to fall into calcium chloride solution. Beads have been produced containing either indomethacin or sulphamethoxazole as model drugs and either dextran or amylose to modify drug release. The beads formed were spherical in shape and had drug loading efficiencies of 80-95% for indomethacin and 60-90% for sulphamethoxazole. Thermal analysis indicated that there was no change in the form of the drugs after incorporation into the beads but that an interaction may have occurred between the pectin and either the dextran or amylose. Swelling of all the beads was similar, with a minimum occurring at pH 3. Drug release was related to the solubility of the compound, with sulphamethoxazole releasing more rapidly than indomethacin at all pH values. Indomethacin release was minimal at pH 3 and 5 but was significant at pH 7.4. However, the inclusion of amylose restricted the release at pH 7.4. When pectinolytic enzymes were included in the dissolution media, release was rapid. The results show that for a relatively insoluble compound, release in the conditions akin to the upper gastrointestinal tract can be minimized by the inclusion of amylose, without affecting the ability of the beads to break down in the presence of pectinolytic enzymes.