Racial differences in pharmacodynamic response to nicotinates in vivo in human skin: black and white

This study evaluated the vasodilation induced in young whites and blacks by topical application of two nicotinates, methylnicotinate (MN) and hexylnicotinate (HN) at the same concentration and in the same vehicle. To assess the influence of skin surface lipids and water content of the stratum corneum on the penetration of the substances, the drugs were applied on the back, on untreated skin and pre-occluded and pre-delipidized sites. Skin blood flow was monitored with laser Doppler velocimetry. The initial response recorded at 15 min (IR), the peak response (PR) and the area under the curve (AUC) were used to characterize the pharmacodynamic response. Statistically significant racial differences in the penetration of nicotinates were detected for the area under the response curve in the untreated and occluded sites, for the initial response and peak response in the pre-occluded site. Occlusion increased (even though not significantly) penetration, except for blacks in the methylnicotinate experiment. Delipidization elicited significantly lower responses for the IR and PR in the MN study, rendering the penetration similar in the two groups. No major differences were recorded between the two nicotinates. The effect of delipidization was most noticeable in blacks in the MN study. We suggest that there are racial (blacks vs. whites) differences in percutaneous penetration of nicotinates, with decreased levels in black skin recorded in all sites investigated.