In situ forming lyotropic liquid crystalline systems containing metronidazole-benzoate

Lyotropic liquid crystals are usually formed from water and one or two surfactants and possibly cosurfactants and oils within a definite concentration and temperature range. The aim of this study was to evaluate self-forming lyotropic liquid crystalline systems for pharmaceutical use, which consist of oils and surfactants with good physiological tolerance and possess a suitable drug release profile. For determining the liquid crystalline structure, polarization microscopy and rheological examinations were used. The drug release studies were performed in vitro with a vertical diffusion cell. Based on the structure examinations it can be stated that the investigated water-free compositions turn spontaneously into high-viscous lyotropic liquid crystalline systems by water absorption, in this way they are proper formulations for in situ gelling drug delivery systems. On the basis of the drug release examinations we can conclude that a considerable amount of the drug was released in the course of the examination and the chemical entity of the surfactant exerted major influence on drug liberation.