Water-filtered infrared-A (wIRA) can act as a penetration enhancer for topically applied substances Wassergefiltertes Infrarot A (wIRA) kann als Penetrationsverstärker für topisch aufgetragene Substanzen wirken

Background:Water-filteredinfrared-A(wIRA)irradiationhasbeenshown to enhance penetration of clinically used topically applied substances 1 Methods: The penetration profiles of the hydrophilic dye fluorescein and the lipophilic dye curcumin in separate standard water-in-oil emul- plication of the formulations. Main variable of interest was the ratio of the amount of the dye in the deeper (second) 10% of the stratum corneum to the amount of the dye in the upper 10% of the stratum corneum. Results: The penetration profiles of the hydrophilic fluorescein showed in case of pretreatment or treatment with wIRA (modes B and C) an in- creased penetration depth compared to the non-irradiated skin (mode A): The ratio of the amount of the dye in the deeper (second) 10% of the stratum corneum to the amount of the dye in the upper 10% of the stratum corneum showed medians and interquartile ranges for mode A of 0.017 (0.007/0.050), for mode B of 0.084 (0.021/0.106), for modeCof0.104(0.069/0.192)(differencebetweenmodes:p=0.0112, significant; comparison mode A with mode C: p<0.01, significant). In contrast to fluorescein, the lipophilic curcumin showed no differences in the penetration kinetics, in reference to whether the skin was irradi- ated with wIRA or not. These effects were confirmed by laser scanning microscopy.Water-filteredinfrared-Airradiationincreasedthehydration of the stratum corneum: transepidermal water loss rose from approxi- mately 8.8 g m -2