Enhanced transdermal delivery of local anesthetics by liposome formulation of local anesthetic mixture

Various concentrations of either lidocaine or tetracaine, plus combinations of lidocaine and tetracaine were formulated into liposomes to improve topical anesthesia. The topical anesthetic effects of these liposomal mixtures of local anesthetics (Lipo-MLA) were then compared with those of EMLA (Eutectic Mixture of Local Anesthetics) and single local anesthetic liposomes using a pinprick test on healthy adult volunteers. The Lipo-MLA exhibited significantly improved anesthetic effects compared to the EMLA and single local anesthetic liposomes with a faster onset time of approximately thirty minutes and duration of at least four hours. A dermal toxicity study using rats revealed that Lipo-MLA was safe at greater than 2,000 mg/kg bodyweight.