European Journal of Clinical Pharmacology

, Volume 21, Issue 1, pp 77–81

Protein binding of drugs in plasma, interstitial fluid and tissues: Effect on pharmacokinetics

  • E. M. Faed

DOI: 10.1007/BF00609592

Cite this article as:
Faed, E.M. Eur J Clin Pharmacol (1981) 21: 77. doi:10.1007/BF00609592


Drug binding in the interstitial fluid as well as in the plasma must be taken into account when considering the pharmacokinetics of drugs which are highly bound to plasma proteins and have a relatively small apparent volume of distribution (V). The half-life and apparent volume of distribution of such a drug can be affected significantly by changes in the extent of binding of the drug in both the plasma and the interstitial fluid. An alteration in the fraction of drug in the tissues which is unbound will primarily affect the pharmacokinetics of drugs which have a relatively large apparent volume of distribution. The effect of changes in the plasma free fraction of drug (fP) on tissue binding can be deduced from a plot of fP versus V, but not from a plot of fP versus β.

Key words

protein-bindingtissue bindinginterstitial fluidplasma proteinvolume of distributionhalf-life

Copyright information

© Springer-Verlag 1981

Authors and Affiliations

  • E. M. Faed
    • 1
  1. 1.MRC Toxicology Research UnitUniversity of Otago School of MedicineDunedinNew Zealand