(i) In vivo CRS was validated as a technique to measure SC thickness on both palmoplantar and, particularly, on nonpalmoplantar skin sites. (ii) Moisturizers improve skin moisturization but in this study only formulation A improved SC thickness, water gradients and hydration as measured by CRS. We hypothesize that this was due to compositional differences between the products. We believe that niacinamide (nicotinamide, vitamin B(3)) is probably contributing significantly to this effect, as it has been proven to increase epidermal lipogenesis and SC barrier function in other studies. These results show that by using CRS, we were able for the first time to determine the effect of moisturizer on multiple SC barrier endpoints including SC thickness, and water content as a function of depth and total SC water content.

Background:The GlucoWatch ® Biographer uses reverse iontophoresis to extract glucose across the skin to monitor glycemia in diabetes. The invasive daily calibration with a conventional "fingerstick" has been perceived as a disadvantage. We used an "internal standard" to render the approach completely noninvasive. Methods: The simultaneous extraction of glucose and sodium by reverse iontophoresis was performed on human volunteers over 5 h, and blood glucose was measured in the conventional manner at each collection interval. These data were used for each volunteer to calculate an extraction constant (K), which equals the ratio of the extracted fluxes ( J Glucose /J Na ϩ) normalized by the corresponding ratio of the concentrations in the blood ([Glucose]/[Na ؉ ]). The values of K were compared between and within volunteers. Results: The iontophoretically extracted glucose flux reflected the glucose concentration profiles in the blood, and sodium extraction remained essentially constant, consistent with the fact that its systemic concentration does not vary significantly. A constant value of K was established for two thirds of the study population. However, the efficiency of glucose extraction varied seasonally, whereas the reverse iontophoresis of Na

Reverse iontophoresis uses a small low electric current to noninvasively extract blood analytes, e.g., glucose, across the skin. The simultaneous quantification of the analyte extracted and of an additional endogenous substance of fixed and known concentration in the body permits the blood level of interest to be found without the need for an invasive calibration procedure. The transport phenomena underlying this approach, applied to glucose monitoring, has been investigated in vitro, using Na+ and neutral model solutes as endogenous "internal standards" (specifically, urea, glycerol, mannitol, and sucrose). The cathodal extracted fluxes of glucose under conditions of modified skin permselectivity were related to those of the different, potential internal standards. Flux ratios depended upon the iontophoretic conditions and the size of the neutral internal standards, whereas high variability was observed with Na+. Constant flux ratios were obtained with mannitol, glycerol, urea, and sucrose for which the mechanism of electrotransport was identical to that of glucose. The advantage of using a neutral internal standard, however, must be weighed against the need to identify and validate the marker under physiological conditions and the additional analytical chemistry necessary for the practical quantification of this substance.