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 vasodilation 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 (E_mx); (b) the area under the erythematous diameter versus time curve (AUE); (c) the maximum LDV response (L_mx); and (d) the area under the LDV response versus time curve (AUL). At p<0.05, AUL (black)>AUL (caucasian) for all MN concentrations; AUL (oriental)>AUL (caucasian) for the higher dose levels. E_mx, AUE and L_mx showed no significant differences between races within concentrations. For all subjects, E_mx AUE, and AUL were significantly dependent on MN dose whereas L_mx 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.