Less painful alternatives for local anesthesia.
BACKGROUND: Infiltration of commonly used local anesthetics is painful. It has been speculated that the pain on infiltration is a direct consequence of the acidity of the anesthetic solution. OBJECTIVE: To compare the degree of pain of intradermal infiltration and the duration of anesthesia for 1% lidocaine with epinephrine 1:100,000, 1% lidocaine with epinephrine 1:100,000 with 80 meq/L sodium bicarbonate, bacteriostatic saline solution with 1% lidocaine with epinephrine 1:300,000, and bacteriostatic saline solution with 1% lidocaine with epinephrine 1:100,000. METHODS: The study was performed in three phases: 1) double-blind comparison study, 2 and 3) open clinical trials. RESULTS: Bacteriostatic saline solution with epinephrine 1:300,000 is significantly less painful on intradermal infiltration than lidocaine with epinephrine 1:100,000 with sodium bicarbonate 80 meq/mL. The saline preparation is an effective anesthetic alternative for superficial surgical procedures such as shave and scissors excision, light curettage and electrodesiccation, and superficial CO2 laser vaporization. CONCLUSION: The pH values of bacteriostatic saline solution with epinephrine 1:300,000 and lidocaine with epinephrine diluted with bacteriostatic saline solution are 5.3 and 4.2, respectively. Both were found to be less painful than 1% lidocaine with epinephrine with sodium bicarbonate 84 meq/mL, which had a pH of 7.4. It is unlikely that the pain of infiltration is a simple function of the pH of the anesthetic solution.