FORMULATION AND CHARACTERIZATION OF ACTIVATED CHARCOAL AND METRONIDAZOLE LAYERED TABLETS AND EVALUATION OF THE IN VIVO PERFORMANCE OF METRONIDAZOLE – ACTIVATED CHARCOAL FORMULATION IN SPRAGUE DAWLEY® RAT MODEL INFECTED WITH ESCHERICHIA COLI O157:H7

Background: Due to Escherichia coli O157:H7 bacteria’s peculiar biochemical characteristics it is considered an emerging pathogen. The aim of this study is to  design, develop and evaluate the  efficacy of a  single  formulation  combining  adsorptive  and   anti infective  properties  in  the   treatment of  diarrhoea  caused  by  Escherichia coli O157:H7  in an animal model. Method: A bilayered tablet of metronidazole and activated charcoal (AC) formulated via direct compression was developed using hydrophilic mucoadhesive polymer xanthan gum in varying concentrations to ensure modified release of metronidazole in the first layer and activated charcoal with microcrystalline cellulose for instant disintegration in the second layer. Escherichia coli infected Sprague Dawley^® rats was utilized to evaluate the efficacy of the formulation. Results: Swelling studies reflected an affinity for the polymer to swell in pH 6.8 where drug release and swelling was influenced by ionic strength of the medium owing to the conformational changes in the xanthan gum in this media with an increase in the zeta charge from -28.5 mV to -40.2 mV, drug release being predominantly by zero order. Treatment with activated charcoal and metronidazole reflected a negative result for identification of Escherichia coli O157:H7 by the third day of treatment in stool with symptoms cessation occurring by the second day of treatment. Conclusion: The synergistic potential of a nitro-imidazole and an adsorbent has been evaluated and established with treated groups showing cessation of symptoms within twenty four hours thus effective in the treatment of Escherichia coli O157:H7 associated diarrhea.