Polymers such as Hyaluronic acid (HA), Polyethylene glycol-400 (PEG-400) and Xanthan Gum (XG) are promising in drug delivery applicationsbecause of their biomedical and pharmaceutical potential applications. In HA 2%-PEG 400 systems, the effect of pH and PEG-400 concentration were evaluated. The viscosity of HA-PEG 400 formulations slightly increased with PEG-400 concentration. Viscoelastic properties and shear thinning character was strongly dependent on pH. Structured systems were obtained at pH 3, with an increase of several orders of magnitude in zero-shear viscosity values. When XG 1% structured system is added on HA (0, 0.5, and 2%) and PEG-400 5%, a sharp increase of viscosity can be observed, obtaining a gel-like behaviour for HA 0.5%-XG 1%-PEG 400 5% formulation. Finally, metronidazole release profiles in HA 2% formulations with different PEG-400 concentrations at pH 4.5 were studied. At least 90% of metronidazole was releasedat 24 h. However, the addition of XG 1% to the HA (0.5 and 2%)-PEG 400 5% systems delayed the drug release. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41313.