Guar gum as potential film coating material for colon-specific delivery of fluorouracil

The potential of guar gum as a film coating material for colon-specific delivery of 5-fluorouracil is evaluated in this study. The guar gum-based multi-unit pellet system is prepared by coating guar gum and pH-sensitive polymer Eudragit FS30D sequentially around drug-loaded non-pareil cores in a fluid-bed coater. The outer Eudragit FS coating protects the system against gastrointestinal environment and dissolves rapidly in distal small intestine, where a lumen pH of over 7 triggers the dissolution of the enteric polymer. The inner guar gum coating works as a time-controlled retardant and offers additional protection of the pellets until it is degraded by microbial enzymes at the proximal colon. In vitro results indicate that guar gum is a feasible coating material to achieve timed and enzyme-triggered fluorouracil release. Pharmacokinetic study in beagle dogs shows delayed absorption of about 5 h and limited absorption fraction as a result of guar gum and Eudragit FS coating.