Local Anesthesia by Topical Application of Lidocaine After Stratum Corneum Ablation with an Er:YAG Laser

Abstract

Background and Objectives: The stratum corneum, the outermost layer of skin, is the principle barrier to permeation of any drug through the skin, including local anesthetics. Removal of the stratum corneum using a pulse of infrared radiant energy could conceivably allow for rapid penetration of topically applied local anesthetic solutions. The purpose of this study was to provide preliminary information on the effectiveness of local anesthesia produced by topically applied lidocaine after ablation of the stratum corneum by an Er:YAG laser. Methods: 50 adult volunteers were enrolled into the study. Participants were divided into two groups (4% lidocaine or 10% lidocaine) and had a site irradiated on the forearm of each arm with a 2.94 micrometer Er:YAG laser. The appropriate concentration of lidocaine was applied for 5 minutes on one arm and 10 minutes on the other. Pinpricks using a 25 gauge 1/2 mm lancet were performed and participants rated the pain using a 0 10 scale. Results: The results of our study suggest that the transdermal administration of topically applied lidocaine is enhanced and topical anesthesia is produced at the site of stratum corneum ablation within 5 minutes. No anesthesia was found in areas tested outside of the ablation site. The ablation of the stratum corneum with the 2.94 micron wavelength radiant energy produced by an Er:YAG laser produced minimal discomfort and resulted in no immediate adverse effects. Conclusions: Results suggest application of topical lidocaine after removal of the stratum corneum using the radiant energy produced by an Er:YAG laser produces rapid local anesthesia at the ablation site.