Comparative study of the efficacy of four topical anesthetics

BACKGROUND. With the emergence of new laser and dermatologic procedures, th e need for more effective topical anesthesia continues to grow. There are n ow several topical anesthetics that are being used prior to laser and surgi cal procedures. OBJECTIVE. TO compare the degree and duration of anesthesia produced by fou r commonly used topical anesthetics, we per formed a prospective study inve stigating the efficacy of EMLA (eutectic mixture of local anesthetics), ELA -Max, 4% tetracaine gel, and betacaine-LA ointment (formerly eutectic-LA). METHODS. Equal amounts of the above topical anesthetics plus a control (euc erin cream) were applied to 10 test sites under occlusion on the volar fore arms of 12 adult volunteers. After a GO-minute application time, the degree of anesthesia was assessed immediately by a Q-switched Nd:YAG laser at 106 4 nm. Pain testing was also performed 30 minutes after the 60-minute applic ation period. Volunteer responses to pain stimuli were recorded using an or dinal scale of 0 (no pain) to 4 (maximal pain). The mean scores for the tim e intervals were obtained. Analysis of the data was performed using analysi s of variance (ANOVA), Newman-Keuls test, Friedman rank order test, and pai red t-tests. RESULTS. ELA-Max, EMLA, and tetracaine were statistically superior to contr ol after the GO-minute application period. Thirty minutes later, ELA-Max, E MLA, tetracaine, and betacaine-LA were all statistically superior to the co ntrol. Comparing individual anesthetics, ELA-Max and EMLA were the superior anesthetics at both time intervals. Although the mean pain scores for each anesthetic were lower 30 minutes after their removal, the differences did not reach statistical signifi cance. CONCLUSION. This is the first prospective study comparing the efficacy of s everal new topical anesthetic agents. Using the methodology of this study, in which the anesthetics were applied under occlusion, ELA-Max and EMLA wer e the superior anesthetics after a 60-minute application time and 30 minute s later. In addition, there was a clinical increase in efficacy suggested w ith all of the anesthetics 30 minutes after their removal.