[Evaluation of adhesive tape containing lidocaine using current perception threshold measurement]

Lidocaine adhesive tape (Penles; Wyeth Lederle Japan, Ltd, Tokyo, Japan) is placed for pain relief prior to puncturing a vein with a needle. We investigated the optimal time interval from application of Penles to vein puncture by measuring current perception threshold (CPT) levels with a Neurometer, by which it was possible to measure the extent of nerve block in a non-invasive and quantitative manner with 3 electrical stimulus rates (2000 Hz, 250 Hz, and 5 Hz). Penles was applied to the dorsum of volunteers' hands for 1, 2, 4, 6 and 12 hours before measuring CPT levels. With a stimulation rate of 2000 Hz and 250 Hz, CPT, levels were found to increase 4 hours after the Penles application, while peak CPT levels for 5 Hz stimulation were observed from 6 to 12 hours after application. However, CPT levels tended to decrease 12 hours after application, regardless of the stimulus rate. From the result, we conclude that Penles provides maximum benefit when applied 6 hours prior to vein puncture.