Comparative study of the efficacy of four topical anesthetics.

BACKGROUND: With the emergence of new laser and dermatologic procedures, the need for more effective topical anesthesia continues to grow. There are now several topical anesthetics that are being used prior to laser and surgical procedures.

OBJECTIVE: To compare the degree and duration of anesthesia produced by four commonly used topical anesthetics, we performed a prospective study investigating 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 (eucerin cream) were applied to 10 test sites under occlusion on the volar forearms of 12 adult volunteers. After a 60-minute application time, the degree of anesthesia was assessed immediately by a Q-switched Nd:YAG laser at 1064 nm. Pain testing was also performed 30 minutes after the 60-minute application period. Volunteer responses to pain stimuli were recorded using an ordinal scale of 0 (no pain) to 4 (maximal pain). The mean scores for the time intervals were obtained. Analysis of the data was performed using analysis of variance (ANOVA), Newman-Keuls test, Friedman rank order test, and paired t-tests.

RESULTS: ELA-Max, EMLA, and tetracaine were statistically superior to control after the 60-minute application period. Thirty minutes later, ELA-Max, EMLA, tetracaine, and betacaine-LA were all statistically superior to the control. 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 significance.

CONCLUSION: This is the first prospective study comparing the efficacy of several new topical anesthetic agents. Using the methodology of this study, in which the anesthetics were applied under occlusion, ELA-Max and EMLA were the superior anesthetics after a 60-minute application time and 30 minutes later. In addition, there was a clinical increase in efficacy suggested with all of the anesthetics 30 minutes after their removal.