TOPICAL LIPOSOMAL LOCAL-ANESTHETICS - DESIGN, OPTIMIZATION AND EVALUATION OF FORMULATIONS

To improve the rate of penetration into the skin, and to develop an ef fective topical anesthetic product, selected local anesthetic agents, benzocaine, lidocaine, dibucaine, etidocaine and tetracaine were encap sulated into liposomes using the solvent evaporation method. After the pilot experiments, tetracaine was selected for further development. E ncapsulation efficiency was determined by centrifugation of liposomes and spectrophotometric analysis of liposome pellets and supernatants. Physical stability and organoleptic properties of the various liposoma l tetracaine formulas were monitored visually and by microscopy for 1 year. Tetracaine was found to be suitable for the development of a lip osomal drug delivery system with high encapsulation efficiency (60-90% ) and physical stability. The results showed that encapsulation effici ency of tetracaine into liposomes can be increased by increasing drug concentration and pH, and including negatively charged stearic acid or unsaturated lipids in the formula. Stability of tetracaine increased with higher encapsulation efficiency, however the shelf life of the pr oduct was still short (2 months). In-process and finished product qual ity control parameters are suggested to facilitate the topical liposom al product development in general.