Cutaneous responses to topical methyl nicotinate in human forearm and vulvar skin

In order to identify and define differences in percutaneous absorption and microcirculatory sensitivity between forearm and vulvar skin we studied the response of human forearm and vulvar (labium majus) skin to topical methyl nicotinate (MN) in 11 healthy premenopausal volunteers. MN-induced erythema was assessed by laser Doppler velocimetry (LDV). The following parameters were compared: 1) basal cutaneous blood flow, 2) the time to peak response, 3) the magnitude of LDV peak response, 4) the area under the LDV response-time curve and 5) the decay time to 75% of peak response. Basal cutaneous blood flow at the vulva was higher than at the forearm (P less than 0.05); the magnitude of peak response was lower at the vulva than at the forearm (P less than 0.01); the area under the curve was lower at the vulva than at the forearm (P less than 0.001); the decay time to 75% of peak response was shorter at the vulva than at the forearm (P less than 0.001). The time to peak response showed no significant differences between sites. The results indicate that the MN-induced vasodilatation is less intense and lasts shorter in vulvar compared to forearm skin.