Study Design: Controlled laboratory study. Objectives: To determine the time course of dexamethasone sodium phosphate (Dex-P) iontophoresis delivery to underlying tissues using microdialysis. Background: The efficacy of iontophoresis at delivering Dex-P through the skin is unknown in humans because of the lack of minimally invasive measurement techniques. Methods: Sixty-four healthy male participants (age = 24.4 ± 3.3 yrs, height = 71.8 ± 2.5 in, weight = 181.8 ± 26.1 lbs) were randomly assigned into one of six groups: 1) 1 mA current, 1 mm probes depth ; 2) 1 mA current, 4 mm probes depth; 3) 2 mA current, 1 mm probes depth; 4) 2 mA current, 4 mm probes depth; 5) in vivo retrodialysis; and 6) skin perfusion flowmetry. Microdialysis probes assess the combined recovery (Dextotal) of Dex-P, dexamethasone (Dex) and its metabolite. In vivo calibration of the microdialysis probes occurred via retrodialysis. Laser Doppler flowmetry assessed skin perfusion. Results: There was no difference of Dextotal between current intensities (P = 0.99) but a greater amount of Dextotal was recovered by the 1 mm probe (P < 0.0001) compared to the 4 mm probe. Peak means for the 1 and 2 mA at 1 mm were 10.8 ± 8.1 and 7.7 ± 5.5 μg/ml and at 4mm being 2.0 ± 0.8 and 1.3 ± 0.9 μg/ml, respectively. Skin perfusion rapidly increased during both current intensity treatments, but significantly decreased before the conclusion of the 1 mA treatment (P < 0.0001). Peak skin perfusion was 741.4 ± 408.7% and 711.6 ± 260.8% baseline for 1 and 2 mA intensities, respectively. Conclusion: Iontophoresis delivery of Dex-P was successful measured in vivo through human skin. Significant concentrations of Dextotal were found regardless of current intensity. Though current induced vasodilation occurred, it did not significantly affect the tissue accumulation of Dextotal.



College and Department

Life Sciences; Exercise Sciences



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transdermal drug delivery, iontophoresis, dexamethasone, microdialysis