Many decisions in drug development and medical practice are based on measuring blood concentrations of endogenous and exogenous
molecules. Yet most biochemical and pharmacological events take place in the tissues. Also, most drugs with few notable exceptions
exert their effects not within the bloodstream, but in defined target tissues into which drugs have to distribute from the
central compartment. Assessing tissue drug chemistry has, thus, for long been viewed as a more rational way to provide clinically
meaningful data rather than gaining information from blood samples. More specifically, it is often the extracellular (interstitial)
tissue space that is most closely related to the site of action (biophase) of the drug. Currently microdialysis (μD) is the
only tool available that explicitly provides data on the extracellular space. Although μD as a preclinical and clinical tool
has been available for two decades, there is still uncertainty about the use of μD in drug research and development, both
from a methodological and a regulatory point of view. In an attempt to reduce this uncertainty and to provide an overview
of the principles and applications of μD in preclinical and clinical settings, an AAPS-FDA workshop took place in November
2005 in Nashville, TN, USA. Stakeholders from academia, industry and regulatory agencies presented their views on μD as a
tool in drug research and development.
Key words clinical pharmacology - microdialysis - recovery - regulatory aspects
The views expressed in this paper are those of the authors and do not necessarily reflect the opinions of their companies/institutions
or the official policy of the FDA. No official support or endorsement by the FDA is intended or should be inferred. The contents
of this report were presented by the authors at the Microdialysis Workshop, Nashville, TN, Nov 4–5, 2005 organized by American
Association of Pharmaceutical Scientists and Co-Sponsored with the US Food and Drug Administration.