Factors critical to iontophoretic assessment of vascular reactivity: implications for clinical studies of endothelial dysfunction.

Skin microvascular responses to iontophoresis of acetylcholine, an endothelium-dependent vasodilator, and sodium nitroprusside, an endothelium-independent vasodilator, were measured using a laser Doppler imager whose software controlled iontophoretic current delivery in an integrated fashion. A novel feature involved monitoring voltage across the iontophoresis chambers during current application (total charge: 8 mC). Both drugs elicited vasodilatation but with differing magnitudes and time courses, whereas current delivery with only vehicle (0.