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Thermodynamic basis for expressing dose logarithmically.

Waddell WJ

Department of Pharmacology and Toxicology, University of Louisville School of Medicine, Louisville, Kentucky, USA. bwaddell@louisville.edu

The current explanations for using a logarithmic scale for the dose of a chemical, administered to a biological system, have all been empirical. There is a fundamental, thermodynamic reason why a logarithmic scale must be used. The chemical potential is the effect that a chemical exerts on any system, including biological systems. The chemical potential of a chemical in any system is directly proportional to the logarithm of its activity or concentration. Lack of understanding of this concept and the consequent use of a linear scale for dose has led to misinterpretation of many biological experiments.

Published 14 April 2008 in Toxicol Appl Pharmacol, 228(2): 156-7.
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