Neutralized lidocaine: use in pain reduction in local anesthesia

The effect of pH neutralization on the pain experienced during intradermal lidocaine administration was investigated in a prospective blind study of 20 adult volunteers. A plain solution (pH congruent to 6.1) and three different buffered solutions of 1% lidocaine (pH values of 6.8, 7.0, and 7.2) were prepared, and a 0.5-mL intradermal injection of each was administered to the volar aspect of the forearm. Pain associated with lidocaine infiltration was rated with a linear visual analogue scale. Solutions with a pH of less than 6.8 (unbuffered lidocaine in this study) predictably produced a burning pain sensation on injection. However, buffering of 1% lidocaine above a pH of 6.8 significantly (P less than .05) reduced the mean quantitative pain estimates compared with the nonbuffered controls.