Effective Duration of iontophoretic Anesthesia

After an arm was given an electrical charge for 9 minutes at 1.5 mA using a handmade iontophoresis apparatus, the effective duration of iontophoretic anesthesia with 1.0% procaine, 1.0% lidocaine, 0.3% dibucaine and 1.0% mepivacaine was measured with a temperature sensory tester at 50°, using a1 grm needle for pain and a brush for touch. Also the painless depth in skin was measured by puncturing with a 21G needle. Procaine, lidocaine and mepivacaine were found to be better for iontophoretic anesthesia. In the case of lidocaine, the effective duration and the painless depth were found to be depen-dent on both the concentration and volume of the lidocaine. But 4% solution of lidocaine may be the limit for getting the deepest effective distance at a 1.5 mA electrical charge for 9 min, when a positive electrode is a circular area of φ20mm.