ABSTRACT
Liquid crystals have been widely used as drug delivery systems for several drugs and several routes of administration, including skin applications. These systems are formed by amphiphilic molecules in the presence of water and show properties of both liquid and solid states. Liquid crystals have been used as drug delivery systems in several forms, such as bulk liquid crystalline gels, liquid crystalline precursors and dispersed systems. Liquid crystalline mesophases are formed when amphiphilic molecules spontaneously form thermodynamically stable, self-assembled structures in the presence of water, and they exhibit several arrangements, such as lamellar, cubic, hexagonal phases. The formation of liquid crystalline phases by a polar lipid and water is affected by several factors, such as the molecular structure of the lipid molecule, water content of the system, temperature, pH, pressure, and addition of a third substance. Liquid crystalline systems can be used as carriers for several drugs and can provide a slow drug release matrix for different routes of administration.
