Topical delivery of lidocaine in healthy volunteers by electroporation, electroincorporation. or iontophoresis: An evaluation of skin anesthesia

Background and Objectives: This study was designed to compare the onset, du ration, and depth of local anesthesia after the topical deliver of lidocain e using electroporation (EP), electroincorporation (EI), and iontophoresis (IP) in healthy volunteers. EP and EI were performed with prototype devices and IP with a commercial drug/device product. Methods: A double-blind, crossover study design was used for 10 randomized volunteers selected for EP treatment with either 4%. 10%. or 20% lidocaine or placebo normal saline. Because it was impossible to blind between IF. EP , and Fl. an open label study with randomized volunteers was selected for I P and EP treatments. Onset and duration of anesthesia was determined by mea suring warm sensation, cool sensation. and hot pain; depth of anesthesia wa s determined by measurement of pain sensation to a 27-gauge needle passed t hrough the skin. Results: For EP, all concentrations of lidocaine produced significant chang es from baseline on 2 or 3 efficacy measures, however, the 4% concentration appeared to be the most efficacious when delivered by the EP method. The E P and EI methods produced a significant elevation in all 3 thermal threshol ds, whereas IP produced significant elevations in cool and warm thresholds only. However. IP resulted in a greater depth of anesthesia. Plasma lidocai ne levels were undetectable. Conclusions: The transdermal delivery of lidocaine by IF, EP, and EI result s in similar surface skin anesthesia: however, IP results in a greater dept h of anesthesia.