Abstract
Accurately predicting in vivo metabolic clearance from in vitro liver microsomes or hepatocytes requires a good understanding of the factors contributing to the prediction. Although much work has concentrated on deriving scaling factors and optimizing the metabolic stability techniques for consistency and rigor, it is only relatively recently that the importance of binding to microsomes and hepatocytes has been appreciated. Ultrafiltration is often used to estimate binding to plasma proteins and microsomes, but the level of nonspecific binding (NSB) to the ultrafiltration apparatus has not been adequately described. We derive an equation to correct for NSB and demonstrate that this can significantly affect the estimate of binding to microsomes and improve the accuracy of scaling to in vivo clearance for a series of barbiturates.
Footnotes
This work was funded by AstraZeneca.
Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
doi:10.1124/dmd.111.040683.
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The online version of this article (available at http://dmd.aspetjournals.org) contains supplemental material.
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ABBREVIATIONS:
- NSB
- nonspecific binding
- HPLC
- high-performance liquid chromatography
- MTBE
- methyl tertiary-butyl ether
- AUC
- area under the curve
- fu
- fraction unbound
- fumic
- fraction unbound to microsomes
- fuinc
- fraction unbound in incubate
- Clint
- intrinsic clearance
- SRW
- standard rat weight.
- Received June 10, 2011.
- Accepted August 31, 2011.
- Copyright © 2011 by The American Society for Pharmacology and Experimental Therapeutics
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