Formulation and Evaluation of Compression Coated Meloxicam Tablets for Colon Drug Delivery

A novel dual tablet formulation for oral administration using xanthan gum as the carrier and meloxicam as a model drug has been investigated for colonspecific drug delivery using invitro methods. The tablets were evaluated for hardness, thickness, drug content uniformity, and were subjected to invitro drug release studies under conditions mimicking mouth to colon transit and the results of which shown that xanthan gum protects the drug from being released completely in the physiological environment of stomach and small intestine. Studies in pH7.4 phosphate buffer saline (PBS) containing rat caecal contents have demonstrated the susceptibility of xanthan gum to the colonic bacteria enzyme action with consequent drug release. The pretreatment of rats orally with 1ml of 2%w/v aqueous dispersion of xanthan gum for 3 days induced enzymes specifically acting on xanthan gum thereby increasing drug release. A further increase in drug release were observed with rat caecal contents obtained after 7 days of pretreatment, because of microbial degradation. Combination of xanthan gum and HPMC provided better protection of drug containing core, showing increased release lag time and controlled release rate. Release of drug from compression coated tablets began after a time delay as a result of hydrogel swelling/retarding for most of the formulations studied. The in-vivo X-ray studies showed that, the tablets reached the colon; not being disintegrated in the upper region of the GI system in all subjects. The FTIR data indicated no possible interaction between meloxicam and carriers.