PURPOSE: 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.

METHODS: 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.

RESULTS: 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.

CONCLUSION: 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.