[Optimal application time of lidocaine adhesive tape examined using current perception threshold measurement]

We often use lidocaine adhesive tape (Penles, Wyeth Lederle Japan, Ltd., Tokyo, Japan) as a topical anesthetic prior to puncturing a vein with a needle. Since the tape is usually in place for a long time, we often experience problems with creasing and flaring when inserting the needle. We attempted to determine the optimal time for application of the tape as well as for vein puncture after its removal by measuring pain sensation in human subjects.

Lidocaine tape was applied to the dorsum of volunteer hands for 2, 4, 6, and 12 hours, and we evaluated changes after removal by determining current perception threshold (CPT), pain score, touch sensation score, diameter of the vein, pruritus, and flare.

CPT levels were found to increase within 1 hour after removal of the lidocaine tape with all 3 electrical stimulus rates used (2000 Hz, 250 Hz, 5 Hz). Further, pain and touch sensation scores were low within 2 hours of removal regardless of application time. Notably, with 4 and 6 hours of application, scores were stable 4 and 6 hours after removal. However, vein diameter and pruritus results did not change regardless of application time, while crease and flare were only observed within 30 minutes after removal.

We concluded that lidocaine tape provided maximum pain relief when applied 4 to 6 hours prior to vein puncture and up to 1 hour after removal.