Cutaneous responses to topical methyl nicotinate in black, oriental, and caucasian subjects

The response of human skin to topical methyl nicotinate (MN) has been monitored in black, oriental, and caucasian subjects. The study aimed to address the question: "Do racial differences in percutaneous absorption and microcirculatory sensitivity exist?" MN-induced vasodilatation was assessed visually and by laser Doppler velocimetry (LDV). At three dose levels, in the three subject populations, four parameters were compared: (a) the diameter of the maximum visually perceptible erythematous area (Emx); (b) the area under the erythematous diameter versus time curve (AUE); (c) the maximum LDV response (Lmax); and (d) the area under the LDV response versus time curve (AUL). At p less than 0.05, AUL (black) greater than AUL (caucasian) for all MN concentrations; AUL (oriental) greater than AUL (caucasian) for the higher dose levels. Emx, AUE and Lmx showed no significant differences between races within concentrations. For all subjects, Emx, AUE, and AUL were significantly dependent on MN dose whereas Lmx was not. The results suggest that some racial differences in response to topical MN exist and that perception of these distinctions may depend upon the method of measurement.