Evaluating Skin Anesthesia After Administration of a Local Anesthetic System Consisting of an S-Caine™ Patch and a Controlled Heat-Aided Drug Delivery (CHADD™) Patch in Volunteers

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Abstract
The objective of this study was to evaluate the depth and duration of skin anesthesia after the administration of a local anesthetic system consisting of an S-Caine (Zars, Salt Lake City, UT) patch coupled with a controlled heat-aided drug delivery (CHADD; Zars) patch. The study design was a randomized, double-blind, placebo-controlled, two-period crossover trial. Twelve healthy adult volunteers between the ages of 18 and 50 years were enrolled. After administration of the study drug or placebo, vital signs (blood pressure, pulse, respiratory rate) were monitored and recorded, and depth and duration of anesthesia were determined and recorded at defined intervals for 10 to 120 minutes after treatment. Depth of anesthesia was measured with a 21-gauge short-bevel needle attached to a depth gauge, and duration was measured using a 0 to 2 (0 = no sensation, 1 = dull sensation, 2 = sharp scratching sensation) verbal report scale. Statistically significant differences were noted in both depth and duration of anesthesia between the active and placebo groups. The posttreatment mean for anesthetic depth in the active group was 6.8 mm compared with 4.7 mm for control group (p = 0.050). The median anesthetic duration was greater than 120 minutes for the active group compared with less than 10 minutes for the placebo group (p = 0.001). The local anesthetic system consisting of a combination of S-Caine and CHADD patches provided a statistically significant dermal anesthesia effect compared with placebo in this volunteer study. If confirmed in other studies, this system has promise as a noninvasive method of producing dermal anesthesia for minor surgical procedures or intravenous insertion.