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22884 Mexiletine (MEX)

Mexiletine (MEX)
Test Code: MEX
Synonyms/Keywords
​Mexitil (Mexiletine)
Useful For
Assessing achievement of optimal therapeutic concentrations
 
Assessing potential toxicity​
Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)		 Pediatric Minimum Volume
(no repeat)
Serum​ ​Red Top Tube (RTT) ​ ​1.5 mL 0.5 mL​ ​
Collection Processing Instructions
​Samples should only be collected after patient has been receiving mexiletine for at least 3 days. Trough concentrations should be collected just before administration of the next dose. Centrifuge within 2 hours of draw and aliquot to remove serum from spun RBCs. 
Specimen Stability Information
Specimen Type Temperature Time
Serum ​ ​ Refrigerated (preferred) ​28 days
​Frozen ​28 days
​Ambient ​28 days
Rejection Criteria

​Serum from Serum Separator Tube (SST)

Interference

​Specimens that are obtained from gel tubes or anticoagulate collections can cause assay interference.

Performing Laboratory Information
Performing Location Day(s) Test Performed Report Available
 Methodology/Instrumentation
​Mayo Clinic Laboratories Monday through Saturday​ 2 to 5 days
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)​
Reference Lab
Mayo Clinic Laboratories
Test Information
Mexiletine is a class I B antiarrhythmic with electrophysiologic properties similar to lidocaine and is useful in suppression of ventricular arrhythmias.
 
The drug exhibits a high degree of oral bioavailability, is approximately 60% protein bound, and undergoes renal clearance. Mexiletine has a volume of distribution of 6 L/kg at a half-life of 11 hours. Myocardial infarction and uremia reduce the rate of clearance and increase the half-life of mexiletine, requiring dosage adjustment guided by drug monitoring.
 
Mexiletine toxicity can occur at concentrations >2.0 mcg/mL (trough value) and is characterized by symptoms of nausea, hypotension, sinus bradycardia, paresthesia, seizures, intermittent left bundle branch block, and temporary asystole.
Reference Range Information
Trough Value:
Therapeutic concentration: 0.5-2.0 mcg/mL
Toxic concentration: >2.0 mcg/mL
Interpretation
Optimal response to mexiletine occurs when the serum concentration is within the range of 0.5 mcg/mL to 2.0 mcg/mL (trough value).
Outreach CPTs
CPT Modifier
(if needed)		 Quantity Description Comments
​80299 ​ ​ ​ ​
Synonyms/Keywords
​Mexitil (Mexiletine)
Ordering Applications
Ordering Application Description
​Cerner ​Mexiletine (MEX)​
If the ordering application you are looking for is not listed, contact your local laboratory for assistance.
Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)		 Pediatric Minimum Volume
(no repeat)
Serum​ ​Red Top Tube (RTT) ​ ​1.5 mL 0.5 mL​ ​
Collection Processing
​Samples should only be collected after patient has been receiving mexiletine for at least 3 days. Trough concentrations should be collected just before administration of the next dose. Centrifuge within 2 hours of draw and aliquot to remove serum from spun RBCs. 
Specimen Stability Information
Specimen Type Temperature Time
Serum ​ ​ Refrigerated (preferred) ​28 days
​Frozen ​28 days
​Ambient ​28 days
Rejection Criteria

​Serum from Serum Separator Tube (SST)

Interference

​Specimens that are obtained from gel tubes or anticoagulate collections can cause assay interference.

Useful For
Assessing achievement of optimal therapeutic concentrations
 
Assessing potential toxicity​
Reference Range Information
Trough Value:
Therapeutic concentration: 0.5-2.0 mcg/mL
Toxic concentration: >2.0 mcg/mL
Interpretation
Optimal response to mexiletine occurs when the serum concentration is within the range of 0.5 mcg/mL to 2.0 mcg/mL (trough value).
For more information visit:
Performing Laboratory Information
Performing Location Day(s) Test Performed Report Available
 Methodology/Instrumentation
​Mayo Clinic Laboratories Monday through Saturday​ 2 to 5 days
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)​
Reference Lab
Mayo Clinic Laboratories
For billing questions, see Contacts
Outreach CPTs
CPT Modifier
(if needed)		 Quantity Description Comments
​80299 ​ ​ ​ ​
For most current information refer to the Marshfield Laboratory online reference manual.