Comparison of Open-Flow Microperfusion and Microdialysis Methodologies When Sampling Topically Applied Fentanyl and Benzoic Acid in Human Dermis Ex Vivo

The purpose of this study is to compare two sampling methods-dermal Open-Flow Microperfusion (dOFM) and dermal Microdialysis (dMD) in an international joint experiment in a single-laboratory setting. We used human ex-vivo skin and sampled topically administered Fentanyl and Benzoic Acid. The second purpose was to provide guidance to researchers in choosing the most efficient method for a given penetrant and give suggestions concerning critical choices for successful dermal sampling. The dOFM and dMD techniques are compared in equal set-ups using three probe-types (one dOFM probe and two dMD probe-types) in donor skin (n = 9) - 27 probes of each type sampling each penetrant in solutions applied in penetrationchambers glued to the skin surface over a time range of 20 h. Pharmacokinetic results demonstrated concordance between dOFM and dMD sampling technique under the given experimental conditions. The methods each had advantages and limitations in technical, practical and hands-on comparisons. When planning a study of cutaneous penetration the advantages and limitations of each probe-type have to be considered in relation to the scientific question posed, the physico-chemical characteristics of the substance of interest, the choice of experimental setting e.g. ex vivo/in vivo and the analytical skills available.