β- Galactosidase mediated release characteristics of lornoxicam loaded guar gum microspheres: evaluation and product development

The present investigation was aimed at developing a novel colon targeted system of lornoxicam based on the use of a combination of pH dependent system (to prevent the premature release of drug in the upper GIT) and enzymatically degradation system (to ensure the specificity of drug release in the colon). The drug loaded guar gum microspheres prepared by emulsification cross-linking method were assessed for the effect of guar gum concentration and the viscosity of external phase on the yield, particle size, entrapment efficiency and in vitro release. The in vitro performance of microspheres showed polymer concentration dependent sustained release and the release data best fitted Higuchi kinetics. Microscopic evaluation of the optimized formulation (M1) revealed spherical particles that comprised drug in amorphous state as deduced by DSC.  DRS revealed zero interaction between drug and guar gum despite the processing steps. The optimized microspheres were formulated as colon targeted tablets by coating with Eudragit S 100 and its sequential analysis in gastrointestinal tract simulated media revealed complete protection against drug release in gastric and intestinal media. In the colon simulated medium (phosphate buffer, pH 6.8 with β-galactosidase enzyme) the drug release was initiated and the tablet M1F3 manifested completed release (97.85 ± 0.48%) of the drug.  The roentegenographic study in rabbits revealed maintenance of tablet integrity up to 7 h and thereafter on reaching the colonic junction the tablet size reduction was initiated due to enzymatic action in colon that was continued till 10th h providing proof of concept for colon targeting efficacy.