Development and evaluation of colon targeted drug delivery system by using natural polysaccharides/polymers

Abstract

Colon is being extensively investigated as a drug delivery site. This study contains comparison of the usual enteric

coating polymers viz. xanthan gum, guar gum, chitosan and ethyl cellulose, as carriers for colon specific drug

delivery. Lactose based metoprolol succinate tablets were prepared. These were coated with one of the coating

polymers to a varying coat thickness. Tablets were prepared using polysaccharides or synthetic polymer as binders.

These included xanthan gum, guar gum, chitosan and ethyl cellulose. Metoprolol Succinate was used as a model

drug. The prepared tablets were enteric coated with kollicoat MAE 100 DP to give protection in the stomach. The

coated tablets were tested in-vitro for their suitability as colon specific drug delivery systems. The drug release

studies were carried out in simulated stomach environment (pH 1.2) for 2 h followed by small intestinal environment

at pH 6.8. The dissolution data obtained from tablets demonstrates that the dissolution rate of the tablet is dependent

upon the type and concentration of polysaccharide/polymer used as binder. The results demonstrate that enteric

coated tablets containing 3% chitosan as a binder, showed only 12.5% drug release in the first 5 h, which is the usual

upper gastrointestinal transit time, whereas, tablets prepared using guar gum as binder, were unable to protect drug

release under similar conditions. Preparations with xanthan gum as a binder formed time-dependent release

formulations. When used in a concentration of 5.92% in the tablets, 28% drug release was observed in the usualupper

gastrointestinal transit time, whereas, tablets prepared using guar gum as binder, were unable to protect drug release

under similar conditions. Preparations with xanthan gum as a binder formed time-dependent release formulations.

When used in a concentration of 5.92% in the tablets, 28% drug release was observed in the usual upper

gastrointestinal tract conditions. It was also found that enteric coated preparation formulated with 8.88% of kollicoat

MAE 100 DP as binder could be used to carry water insoluble drug molecules. The above study shows that chitosan

could be successfully used as a binder, for colon targeting of water insoluble drugs in preference to guar gum when

used in the same concentration. Additionally, formulations developed with chitosan and kollicoat MAE 100 DP