Abstract

Two groups of healthy volunteers, one black, one white, were tested with a topically absorbed mixture of lidocaine and prilocaine in a water base. A visual analog pain scale (VAPS) was used to quantify the level of relative anesthesia. At 1 hour after the placement of the mixture under an occlusive dressing, the cream was wiped off. The group of white patients experienced a 70% reduction (per VAPS) in pain sensation to pin prick, while the black patients experienced only a 40% pain reduction. At 1½ hours, the white patients had a 90% reduction while the black patients had less than an 80% reduction. Over the subsequent hour and a half, virtually all of the members of the white group experienced complete anesthesia, while those of the black group had a leveling off of the anesthetic effect at less than 80%. It appears that there are racial differences between the onset of action and ultimate clinical effectiveness of a cutaneously absorbed mixture of local anesthetics. Several architectural differences between the structure of the skins of black patients and whites are cited and discussed as possible explanations.