Transdermal permeation and biocompatibility studies on gel formulations of benzocaine encapsulated in elastic and conventional liposomes

Abstract

Topical anesthesia is an essential procedure to reduce both pain and discomfort during diagnosis and dermatologic procedures. Our research group has showed the efficacy of a conventional liposomal gel formulation for the local anesthetics ropivacaine and benzocaine in reducing the pain caused by needle insertion in dental anesthesia at the oral mucosa (Franz-Montan et al, 2007ab). The goal of the present study is to determine the in vitro and in vivo permeation rate of elastic and conventional liposome-encapsulated benzocaine (10%) formulations, as well as its toxicity, evaluated by cultured cells tests and after topical application in rat skin. The elastic vesicles will be prepared according to the technique proposed by Honeywell-Nguyen et al. (2002a). The following formulations will be tested: placebo gel of elastic vesicles; placebo gel of conventional liposomes; conventional liposome-encapsulated 10% benzocaine gel; elastic liposome-encapsulated 10% benzocaine gel, 10% benzocaine gel and commercially available 20% benzocaine gel. The biocompatibility of the topical gel formulations will be tested through analysis of histological changes of dermis and epidermis (leukocytes infiltration and/or presence of necrosis area) after application of the formulations at the rat skin. We intend to test the anesthetic efficacy of these formulations on human volunteers, once positive results were obtained. (AU)