title: Topical EMLA pre-treatment fails to decrease the pain induced by 1% topical capsaicin.
abstract: Topical capsaicin has been reported to be beneficial for the treatment of neurogenic pain. However, due to the burning pain associated with topical capsaicin, many patients discontinue treatment before therapeutic benefits are obtained. This study assessed the efficacy of EMLA (eutectic mixture of 2.5% prilocaine and 2.5% lidocaine) to block pain induced by the topical application of 1% capsaicin. Nine healthy subjects (five males and four females) participated in the study. High dose topical capsaicin (1%) was applied to a 2.5 x 2.5 cm region of both volar forearms for 6 h. One arm was pretreated (for 2 h) and cotreated with EMLA, and the other arm served as vehicle control. Average and peak pain ratings were recorded at 15-min intervals using a 0 (no pain) to 10 (worst possible pain) scale. Average and peak pain ratings were significantly lower at the EMLA site during the first 15-30 min of capsaicin treatment. However, for the remaining 5.5 h of capsaicin treatment, the pain ratings at the EMLA and vehicle sites were not significantly different. The 6 h treatment with high dose topical capsaicin (1%) produced significant desensitization to heat stimuli that was not affected by EMLA treatment. EMLA fails to produce a long lasting attenuation of the pain induced by topical application of 1% capsaicin. These results argue against the use of EMLA to block pain to topical capsaicin during the treatment of neurogenic pain.
authors.affiliation: Department of Neurosurgery, Johns Hopkins School of Medicine, 600 North Wolfe Street, Meyer 5-109, Baltimore, MD 21287 USA Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD USA Applied Physics Laboratory, The Johns Hopkins University, Johns Hopkins Road, Laurel, MD 20723, USA.
authors.forename: Perry N
authors.initials: PN
authors.lastname: Fuchs
authors.forename: Marco
authors.initials: M
authors.lastname: Pappagallo
authors.forename: Richard A
authors.initials: RA
authors.lastname: Meyer
mesh_terms: D000287:Administration, Topical; D000328:Adult; D000779:Anesthetics, Local / Q000627:therapeutic use*; D002211:Capsaicin; D004361:Drug Tolerance; D005260:Female; D006801:Humans; D008012:Lidocaine / Q000627:therapeutic use*; D000077442:Lidocaine, Prilocaine Drug Combination; D008297:Male; D008875:Middle Aged; D009437:Neuralgia / Q000139:chemically induced / Q000188:drug therapy*; D017288:Pain Threshold / Q000187:drug effects; D011318:Prilocaine / Q000627:therapeutic use*
chemical_list: D000779:Anesthetics, Local; D000077442:Lidocaine, Prilocaine Drug Combination; D011318:Prilocaine; D008012:Lidocaine; D002211:Capsaicin