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Epic Test Code LAB3815 Mexiletine, Serum

Additional Codes

MML Code: MEX

LIS Code: MXIL

NY State Approved

Yes

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Reporting Name

Mexiletine, S

Method Name

Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Red Refrigerated (preferred) 28 days
  Ambient  28 days
  Frozen  28 days


Specimen Required


Patient Preparation: Specimens 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.

Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Collection Container/Tube: Red top (serum gel/SST are not acceptable)

Submission Container/Tube: Plastic vial

Specimen Volume: 1.5 mL

Collection Instructions:

1. Draw blood immediately before next scheduled dose.

2. Centrifuge and aliquot serum into a plastic vial within 2 hours of collection.


Specimen Type

Serum Red

Specimen Minimum Volume

0.5 mL

Reference Values

Trough Value

0.5-2.0 mcg/mL: Therapeutic concentration

>2.0 mcg/mL: Toxic concentration

Report Available

2 to 5 days

Day(s) Performed

Monday through Friday

CPT Code Information

80299

Reject Due To

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK

Useful For

Assessing achievement of optimal therapeutic mexiletine concentrations

 

Assessing potential mexiletine toxicity

Clinical 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 approximately 6 L/kg and a half-life of approximately 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 above 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.

Interpretation

Optimal response to mexiletine occurs when the serum concentration is within the range of 0.5 to 2.0 mcg/mL (trough value).

Cautions

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

Specimen Retention Time

14 days

Forms

If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.