title: Menthol facilitates the skin analgesic effect of tetracaine gel.
abstract: The aim of this study is to observe the effect of menthol on the percutaneous penetration and skin analgesic action of tetracaine gel (T-gel). Anesthetic gels containing 4% tetracaine in carbomer vehicle with and without menthol were prepared. The menthol penetration-enhanced gel conferred significantly higher diffusion of tetracaine across full-thickness mouse skin than non-penetration-enhanced gel, in a dose-dependent manner. The inter-cellular spaces of the stratum corneum in skin treated with menthol penetration-enhanced gel became extended as compared with those in non-penetration-enhanced gel. This may suggest that menthol's action was related to the changes of the epidermis ultra structures. An enlarged inter-cellular space, per se, would allow a better passage to tetracaine. To determine the efficacy of menthol penetration-enhanced tetracaine gel in the management of pain, a double-blind, placebo-controlled, randomized controlled trial (RCT) design was used. The mean verbal pain scores (VPS) were significantly lower in volunteers treated with penetration-enhanced tetracaine gel than those in volunteers receiving non-penetration-enhanced tetracaine gel or placebo. Menthol improved the analgesic efficacy of the tetracaine 4% gel in part through enhanced percutaneous permeation.
authors.affiliation: Department of Pharmacology, College of Basic Medical Sciences, Shanghai JiaoTong University, South ChongQing Road 280, Shanghai 200025, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
authors.forename: Xun
authors.initials: X
authors.lastname: Ye
authors.forename: Xuemei
authors.initials: X
authors.lastname: Feng
authors.forename: Guanhuai
authors.initials: G
authors.lastname: Zhou
authors.forename: Zhengxing
authors.initials: Z
authors.lastname: Rong
authors.forename: Chao
authors.initials: C
authors.lastname: Fang
authors.forename: Hongzhuan
authors.initials: H
authors.lastname: Chen
mesh_terms: D000328:Adult; D000779:Anesthetics, Local / Q000493:pharmacokinetics / Q000627:therapeutic use*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004338:Drug Combinations; D005260:Female; D005782:Gels; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008610:Menthol / Q000008:administration & dosage / Q000494:pharmacology*; D051379:Mice; D010146:Pain / Q000209:etiology / Q000517:prevention & control*; D011292:Premedication; D012867:Skin / Q000187:drug effects / Q000473:pathology; D012869:Skin Absorption / Q000187:drug effects*; D013748:Tetracaine / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*
chemical_list: D000779:Anesthetics, Local; D004338:Drug Combinations; D005782:Gels; D013748:Tetracaine; D008610:Menthol