Topical EMLA (R) pre-treatment fails to decrease the pain induced by 1% topical capsaicin

Topical capsaicin has been reported to be beneficial for the treatment of n eurogenic pain. However, due to the bunting pain associated with topical ca psaicin, many patients discontinue treatment before therapeutic benefits ar e obtained. This study assessed the efficacy of EMLA(R) (eutectic mixture o f 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 fem ales) participated in the study. High dose topical capsaicin (1%) was appli ed to a 2.5 x 2.5 cm region of both volar forearms for 6 h. One arm was pre treated (for 2 h) and cotreated with EMLA, and the other arm served as vehi cle control. Average and peak pain ratings were recorded at 15-min interval s using a 0 (no pain) to 10 (worst possible pain) scale. Average and peak p ain ratings were significantly lower at the EMLA site during the first 15-3 0 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 signifi cantly different. The 6 h treatment with high dose topical capsaicin (1%) p roduced significant desensitization to heat stimuli that was not affected b y EMLA treatment. EMLA fails to produce a long lasting attenuation of the p ain induced by topical application of 1% capsaicin. These results argue aga inst the use of EMLA to block pain to topical capsaicin during the treatmen t of neurogenic pain. (C) 1999 International Association for the Study of P ain. Published by Elsevier Science B.V.