Less painful alternatives for local anesthesia

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.

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.

The study was performed in three phases: 1) double-blind comparison study, 2 and 3) open clinical trials.

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.

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.