Ternary Blends of some Hydrophilic and Hydrophobic Polymers in Colon Targeted Delivery of Metronidazole

Matrix tablets were prepared using blends of xanthan gum (XG), Guar gum (GG) and ethylcellulose (EC). The polymers were combined using six different ratios; 1:1:1, 1:2:1, 1:2:2, 2:2:1, 2:1:2 and 2:1:1 to produce formulations XG1GG1EC1, XG1GG2EC1, XG1GG2EC2, XG2GG2EC1. XG2GG1EC2 and XG2GG1EC1 respectively. Metronidazole was used as the model drug. The ability of the prepared matrices to target drug release predominantly at the colon under the influence of colonic bacteria was evaluated using the dissolution medium containing 4 % caecal content. Our results show that, optimum drug release was observed with formulations XG2GG2EC1 and XG2GG1EC1 with Cmax of 60 and 76 % respectively. Significant difference (P<0.05) was observed between drug release in dissolution medium with and without rat caecal contents for the batches of Metronidazole tablets. Formulations (XG2GG2EC1 and XG2GG1EC1) followed Higuchi square roots kinetics ( r2 =0.9942) via fickian diffusion ( n < 0.45 ) and Korsemeyer model (r2 = 0.9939) via non fickian diffusion (n > 0.45) respectively.