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Background: Since decades, histamin applications are routinely performed in skin prick tests using a lancet. However, this technique is associated with various drawbacks., Materials and Methods: In healthy human subjects, we investigated the effects of microneedle-enhanced histamin delivery (wheal size, erythema size) in the skin microvasculature using polarized light spectroscopy imaging (Tissue Viability imaging, TiVi). Histamin was applied on microneedle-pretreated skin or on -untreated skin, to assess the microvascular response in the local skin., Results: In our results, histamin was delivered more rapidly into the skin after microneedle pretreatment compared to passive diffusion, visible as wheal and erythema., Conclusion: The here presented technique might be useful for a personalized drug-testing system in the future., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Objective: After iontophoresis of vasoactive drugs into the skin, a decrease in perfusion is commonly observed. We delivered vaso-active drugs by iontophoresis using different delivery protocols to study how these affect this decrease in perfusion as measured using LDF., Methods: We measured skin perfusion during iontophoresis of (ACh), MCh, and NA using a single pulse or separate pulses at different skin sites, and during repeated delivery of ACh at the same site., Results: Perfusion half-life was 6.1 (5.6-6.6) minutes for ACh and 41 (29-69) minutes for MCh (p < 0.001). The maximum response with multiple pulses of ACh iontophoresis was lower than with a single pulse, 30 (22-37) PU vs. 43 (36-50) PU, p < 0.001. Vasoconstriction to NA was more rapid with a single pulse than with multiple pulses. The perfusion half-life of ACh decreased with repeated delivery of ACh at the same site-first 16 (14-18), second 5.9 (5.1-6-9) and third 3.2 (2.9-3.5) minutes, p < 0.001., Conclusions: The drug delivery protocol affects microvascular responses to iontophoresis, possibly as a result of differences in the dynamics of local drug concentrations. Perfusion half-life may be used as a measure to quantify the rate of perfusion recovery after iontophoresis of vasoactive drugs., (© 2015 John Wiley & Sons Ltd.)