Interpretive Handbook

Test 8382 :
Lidocaine, Serum

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Lidocaine is commonly used as a local anesthetic, but is also effective at controlling ventricular arrhythmia and ventricular fibrillation in children and adults. For cardiac therapy, optimal therapeutic response is seen when serum concentrations are between 1.5 mcg/mL and 5.0 mcg/mL. Lidocaine is 50% protein-bound, primarily to alpha-1-acid glycoprotein; concentrations of this protein increase after myocardial infarction, which may decrease the amount of free lidocaine and thus its efficacy.


Lidocaine undergoes extensive first-pass hepatic metabolism and thus is not administered orally. It is eliminated via renal clearance, with a half-life of approximately 1.5 hours. Diseases that reduce hepatic or renal function reduce clearance and prolong elimination of lidocaine.


Toxicity occurs when the concentration of lidocaine is >6.0 mcg/mL and is usually associated with symptoms of central nervous system excitation, light-headedness, confusion, dizziness, tinnitus, and blurred or double vision. This can be accompanied by bradycardia and hypotension leading to cardiovascular collapse.

Useful For Suggests clinical disorders or settings where the test may be helpful

Assessing optimal dosing during the acute management of ventricular arrhythmias following myocardial infarction or during cardiac manipulation such as surgery 


Assessing potential toxicity

Interpretation Provides information to assist in interpretation of the test results

Optimal response to lidocaine occurs when the serum concentration is between 1.5 mcg/mL to 5.0 mcg/mL.  


Toxicity is more likely when concentrations exceed 6.0 mcg/mL.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

No significant cautionary statements

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Therapeutic concentration: 1.5-5.0 mcg/mL

Toxic concentration: >6.0 mcg/mL

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Valdes R Jr, Jortani SA, Gheorghiade M: Standards of laboratory practice: cardiac drug monitoring. National Academy of Clinical Biochemistry. Clin Chem 1998; 44(5):1096-1109

2. "Lidocaine" In Physician’s Desk Reference. November, 2009

3. Harrison DC: Should lidocaine be administered routinely to all patients after acute myocardial infarction?  Circulation 1978;58:581-584