Clinical Chemistry, Vol 25, 617-619, Copyright © 1979 by American Association for Clinical Chemistry

Importance of blood-collection tubes in plasma lidocaine determinations

WW Stargel, CR Roe, PA Routledge and DG Shand

In 25 clinical samples serum lidocaine concentrations fell from a mean of 6.5 +/- 2.1 mg/L (mean +/- SD) to 4.9 +/- 1.8 mg/L (p less than 0.001) when the blood sample was allowed to make contact with the stopper of the Vacutainer collection tube. In vitro experiments showed that this effect of the stopper occurred only with whole blood and was dependent on sample concentration. The plasma binding of lidocaine decreased from a normal value of 56% +/- 2.2 (mean +/- SD) to 28% +/- 2.2 (p less than 0.001) when exposed to the Vacutainer stopper. We conclude that a chemical leached from such stoppers displaces lidocaine from its plasma-binding sites and that the drug is then redistributed into the erythrocytes, producing spuriously low lidocaine concentrations in plasma or serum. Such artifacts are important in therapeutic drug monitoring and can lead to erroneous clinical decisions.

The following articles in journals at HighWire Press have cited this article:

				D. J. Greenblatt, D. M. Benjamin, C. R. Willis, J. S. Harmatz, and M. A. Zinny Lidocaine Plasma Concentrations Following Administration of Intraoral Lidocaine Solution Arch Otolaryngol Head Neck Surg, May 1, 1985; 111(5): 298 - 300. [Abstract] [PDF]

				P. A. ROUTLEDGE, W. W. STARGEL, G. S. WAGNER, and D. G. SHAND Increased Alpha-1-Acid Glycoprotein and Lidocaine Disposition in Myocardial Infarction Ann Intern Med, November 1, 1980; 93(5): 701 - 704. [Abstract] [PDF]