The results obtained are similar to those of human skin, indicating the suitability of this porcine tissue as a model for human skin.

The topical application of drugs, such as nicotinates, affects cutaneous blood flow. Such a biological response, which is dependent on the drug and the individual, can be measured noninvasively using laser Doppler flowmetry. We illustrate the kinetics of vasodilation caused by topically applied benzyl nicotinate using a new frequency-selective laser Doppler flowmeter. This flowmeter measures the blood flow in the superficial dermal plexus and the deeper lying larger capillaries simultaneously and indirectly by determining the flow velocity. Both sets of data are compared with the skin temperature and redness. Four biological parameters are measured consecutively on a skin area treated with gel containing benzyl nicotinate and on an untreated control area. A linear relationship between both blood flows is observed. However, no correlation is obtained between the microcirculation with either the cutaneous temperature or the redness. These results indicate the transport of the drug in the blood from the upper to the deeper capillaries. Cutaneous temperature and redness are unsuitable parameters to measure the kinetics of the blood flow after topical application of drugs.

The removal of the stratum corneum (SC) using adhesive tapes is a common technique in cutaneous studies. The determination of the varying amounts of the SC removed would be a helpful tool in such investigations. In the present study, the cell layers of porcine SC were counted before and after removal of several tape strips using histological techniques. In addition, the pseudo-absorption of the corneocytes reflecting the amount of these cells was determined using spectroscopy. Different amounts of SC were removed using 20 tape strips. The spectroscopically determined data correlate linearly with the number of removed cell layers. Based on these results, the pseudo-absorption of the corneocytes can be used to calculate the absolute number of cell layers removed with a standard deviation of less than 11%. In this way, the SC can be quantified using the procedure of tape stripping in combination with the spectroscopic determination of the corneocytes.

Cutaneous characteristics, e.g., thickness of the SC and density of follicles, affect the penetration of topically applied substances. In the present study, the penetration of benzyl nicotinate, causing a vasodilation, was studied on three anatomic sites (forearm, forehead and calf) differing in their skin characteristics. Therefore, the blood flow of the superficial dermal plexus and that of the larger capillaries in the deeper skin layers was simultaneously measured using a laser Doppler flowmeter. In addition, the cutaneous temperature and redness were determined as a function of time. These four biological reactions were measured in turn on a skin area treated with a gel containing benzyl nicotinate and on an untreated control area. The highest basal levels were observed on the forehead. Topical application of benzyl nicotinate resulted in an increase in each biological response. Compared to the other sites, the maximal values were reached earliest on the forehead, which also showed the fastest decrease. No significant differences were obtained comparing the kinetic data of the calf with that of the forearm. The results indicate an additional contribution by the numerous vellus hair follicles of the forehead to the penetration and exposure of the drug.