Lidocaine Anesthesia: Comparison of Iontophoresis, Injection, and Swabbing

Abstract

The duration and depth of anesthesia produced by lidocaine with three methods of administration were studied. To test duration of anesthesia, either lidocaine or placebo was administered by iontophoresis, subcutaneous infiltration, or swabbing to each of three sites 3 cm apart on the flexor surface of each forearm of 27 subjects. To test for feeling, the tip of a 21-gauge hypodermic needle was pressed on each application site every five minutes until feeling returned. The depth of anesthesia achieved with iontophoresis or infiltration of lidocaine was tested on the flexor surface of each forearm of 12 subjects, with a random assignment of application methods to each arm. Lidocaine iontophoresis produced local anesthesia of significantly longer duration (p less than 0.001) than topical application of lidocaine or placebo by any route of administration, but of significatnly shorter duration (p less tahn 0.001) than lidocaine infiltration. The results showed that lidocaine iontophoresis is an effective method of producing local anesthesia for about five minutes without requiring the use of a hypodermic needle and syringe.