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The Role Of Extracellular Fluid in Biokinetic Modeling

Miller, Guthrie*; Klumpp, John A.; Melo, Dunstana; Poudel, Deepesh

doi: 10.1097/HP.0000000000000722

The pharmacokinetic equations of Pierson et al. describing the behavior of bromide in rat provide a general approach to the modeling of extracellular fluid (ECF). The movement of material into ECF spaces is rapid and is completely characterized by tissue volumes and vascular flow rates to and from a tissue, the volumes of the tissue, and the ECF associated with the tissue. Early-time measurements are needed to characterize ECF. Measurements of DTPA disappearance from plasma by Wedeking et al. are discussed as an example of such measurements. In any biokinetic model, the fastest transfer rates are not determinable with the usual datasets, and if determined empirically, these rates will have very large and highly correlated uncertainties, so particular values of these rates, even though the model fits the available data, are not significant. A pharmacokinetic front-end provides values for these fast rates. An example of such a front-end for a 200‐g rat is given.

*Santa Fe, NM; †Radiation Protection Division, Los Alamos National Laboratory, Los Alamos, NM; ‡Melohill Technology, LLC, Rockville, MD.

For correspondence please contact: Deepesh Poudel, PO Box 1663, MS G761, Los Alamos, NM 87545, or

The authors declare no conflicts of interest.

(Manuscript accepted 9 July 2017)

© 2017 by the Health Physics Society