CUTANEOUS IONTOPHORETIC APPLICATION OF CONDENSED LIDOCAINE

The purpose of this study was to determine whether iontophoretic appli cation of high concentrations of lidocaine, with the same current, wou ld produce cutaneous local anaesthesia rapidly enough for clinical pra ctice. Twenty healthy volunteers, 17 male and three female, were selec ted for study. After five-minutes or ten-minute iontophoresis using li docaine 4, 10, 20, 30, 50%, we assessed the response to pin prick with a 27-gauge sterile needle inserted to the depth of 2 mm at five rando m locations in the iontophoretically-stimulated area. Also, plasma lid ocaine concentrations were measured in the venous blood samples which had been taken from three male subjects, at 3, 10, and 30 min after io ntophoresis with lidocaine 50%. The pain score after five-minute ionto phoresis was higher than that after ten-minute iontophoresis, using ea ch concentration of lidocaine (P < 0.001), whereas the pain scores had no correlation with lidocaine concentration within five-minute and te n-minute iontophoresis groups, respectively (P: NS). On the other hand , plasma lidocaine concentration was <1.0 mu g.ml(-1) in all samples. No side effects other than erythema were observed after iontophoresis using high concentrations of lidocaine up to 50%. These results showed that by increasing the lidocaine concentration of the applied solutio n up to 50%, the application time of iontophoresis cannot be reduced f rom ten to five minutes without losing analgesic effect, although iont ophoresis itself can be performed with safety.