Effect of selected mucoadhesive polymers on pharmaceutical properties of chitosan formulations

The aim of this study was to develop a technical process and composition of mucoadhesive hydrogels containing benzocaine, based on different concentration ratios of the natural polymers chitosan and xanthan gum. For this purpose, lyophilisates of polymeric complexes with the quantitative ratios of 0.5:1, 1:1 and 1:0.5 chitosan to xanthan gum were prepared and subsequently used to prepare hydrogels of various concentrations. The physicochemical properties and pharmaceutical availability of benzocaine were evaluated and diffractograms and Fourier-transform infrared spectra of individual polymers and their polyelectrolyte complexes were compared. The 1:1 formulation exhibited the highest water absorption capacity and the gels showed the highest viscosity and the shortest blurring times. More chitosan increased carrier texture parameters, including hardness, cohesiveness and consistency, whereas more xanthan gum led to the longest gel blurring times and improved carrier stability. The concentration ratio of chitosan to xanthan gum in lyophilisates determined the viscosity, texture, spreadability and blurring time of the gels. Increases in lyophilisate percentage in the gels also affected the physicochemical properties of the carrier. In addition, the proportions of polymers in the mixture did not influence the availability of the drug from the prepared gel; this factor appears to depend more on the lyophilisate content in the carrier. Variations in the ratio of chitosan to xanthan gum in the polymer complex as well as lyophilisate percentage in the gel may impact the properties of the hydrogel and its efficacy as a carrier for therapeutic substances administered to the oral cavity mucosa.