Formulation and characterization of liquid crystal systems containing azelaic acid for topical delivery.

Purpose: The aim of this study is to prepare and characterize azelaic acid (AzA) containing liquid crystal (LC) drug delivery systems for topical use.Methods: Two ternary phase diagrams, containing liquid paraffin as the oil component and a mixture of two nonionic surfactants (Brij 721P and Brij 72), were constructed. Formulations chosen from the phase diagrams were characterized by polarized light microscopy, rheological analyses, differential scanning calorimetry (DSC), and small angle x-ray scattering spectroscopy.Results: Polarized light microscopy proved that except the oil/water emulsion (O/W E), other formulations showed lamellar LC structure. In vitro release studies indicated that the fastest release was achieved by the Lamellar LC (LLC) and O/W E systems, whereas slower release was obtained from the emulsion containing lamellar LC (E-LLC) and distorted lamellar LC (D-LLC) systems. Results of rheological measurements both supported the results of in vitro release studies and showed that the emuls...