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Updated: Aug 11, 2026

Human In-Vivo Bioassay for the Tissue-Specific Measurement of Nociceptive and Inflammatory Mediators
Published on: December 1, 2008
Altered drug binding due to the use of indwelling heparinized cannulas (heparin lock) for sampling
Abstract:
The effect of the use of the so-called heparin lock for blood sampling on the binding of propranolol has been studied and a cumulative dose-response curve to heparin constructed. The use of this method of blood sampling introduced considerable artifactual changes into the measurement of propranolol's plasma binding. The free fraction rose from 9.9% to 13.4% after only 50 U of heparin was used to flush the cannula. The increase in the free fraction of propranolol showed excellent correlation with the increase in free fatty acid levels (p less than 0.001, r = 0.996). The importance of ensuring that sampling techniques do not introduce artifactual changes in pharmacokinetic studies is emphasized.
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