Abstract

This study aimed to investigate the efficacy of both xanthan gum (XG) and guar gum (GG) controlling the release rate of the poorly water soluble drug, indomethacin (IDM) from colon target drug delivery systems. Binary mixtures of the drug and the hydrophilic carrier (XG) in the ratios of 1:1 and 1:2 and tertiary mixture in the ratio of 1:1:1 IDM: XG: GG were prepared using three different approaches namely, physical mixture, co-grinding and solid dispersion. The prepared binary and tertiary systems were compressed into core tablets. The core tablets were evaluated for their drug content, weight variation, hardness, friability and in-vitrodissolution rate study. The dissolution profiles in pH 6.8 buffer solutions revealed that increasing the gum content in the core tablet resulted in a decrease in the IDM release rate.  The core tablets were then coated with two different type of coat (inner and outer). The inner coat consisted of guar gum solutions of different concentrations (0.2, 0.4, 0.6, 0.8% w/v) to prevent the drug release in pH 7.4. Tablets were then coated with an enteric coat by dipping in 5% Eudragit (ER L100) ethanolic solution to inhibit the drug release in pH 1.2. The coated tablets were then dried using hot air. The prepared coated tablets were subjected to release rate study which indicated that the release of the drug was inhibited in pH 1.2 whereas; a low percentage of the drug was released in pH 7.4.  In pH 6.8, the release profiles showed a sustained release of the drug over 18 h. The coated tablets that showed the promising sustained release profiles were further evaluated in pH 6.8 buffer solution containing rat cecal content to study the effect of bacterial degradation on the polysaccharide gums.

Key words: Indomethacin, xanthan gum, guar gum, co-grinding, solid dispersion, dissolution rate, colon target drug delivery systems.