Topical delivery of lidocaine in healthy volunteers by electroporation, electroincorporation, or iontophoresis: an evaluation of skin anesthesia.
OBJECTIVE
This study was designed to compare the onset, duration, and depth of local anesthesia after the topical delivery of lidocaine 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 IP, EP, and EI, an open label study with randomized volunteers was selected for IP and EP treatments. Onset and duration of anesthesia was determined by measuring warm sensation, cool sensation, and hot pain; depth of anesthesia was determined by measurement of pain sensation to a 27-gauge needle passed through the skin.


RESULTS
For EP, all concentrations of lidocaine produced significant changes 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 EP and EI methods produced a significant elevation in all 3 thermal thresholds, whereas IP produced significant elevations in cool and warm thresholds only. However, IP resulted in a greater depth of anesthesia. Plasma lidocaine levels were undetectable.


CONCLUSIONS
The transdermal delivery of lidocaine by IP, EP, and EI results in similar surface skin anesthesia; however, IP results in a greater depth of anesthesia. Reg Anesth Pain Med 2001;26:229-238.
Wallace
M S
MS
Department of Anesthesiology, University of California San Diego, 9500 Gilman Drive #0924, La Jolla, CA 92093, USA.
Ridgeway
B
B
Jun
E
E
Schulteis
G
G
Rabussay
D
D
Zhang
L
L
D000287:Administration, Topical; D000328:Adult; D000772:Anesthesia, Local; D000779:Anesthetics, Local / Q000008:administration & dosage*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D018274:Electroporation; D005260:Female; D006358:Hot Temperature; D006801:Humans; D007478:Iontophoresis; D008012:Lidocaine / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D017288:Pain Threshold; D012684:Sensory Thresholds; D012867:Skin / Q000294:innervation; D014110:Touch
D000779:Anesthetics, Local; D008012:Lidocaine