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Test Code MEXILETINE Mexiletine, Serum

Reporting Name

Mexiletine, S

Useful For

Assessing achievement of optimal therapeutic concentrations


Assessing potential toxicity

Specimen Required

Container/Tube: Red top

Specimen Volume: 3 mL

Collection Instructions:

1. Samples should only be collected after patient has been receiving mexiletine for at least 3 days.

2. Trough concentrations should be collected just before administration of next dose.

Specimen Type

Serum Red

Specimen Minimum Volume

1.1 mL

Specimen Stability Information

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

Day(s) and Time(s) Performed

Monday, Wednesday, Friday; 9 a.m.

Performing Laboratory

Mayo Medical Laboratories in Rochester

Method Name

High-Performance Liquid Chromatography (HPLC)

Method Description

Mexiletine is extracted with an organic solvent from serum at neutral or basic pH, but pH 10.4 is optimal for minimal interference from other drugs and maximal recovery. The organic extract is acidified and then evaporated under a stream of N(2). The residue is taken up in mobile phase and chromatographed by reverse-phase high-performance liquid chromatography (HPLC). Mexiletine is detected by absorbance at 210 nm and quantified by peak height ratios relative to an internal standard, p-chlorodisopyramide.(Mastropaolo W, Holmes DR, Osborn MJ, et al: Improved liquid-chromatographic determination of mexiletine, an antiarrhythmic drug, in plasma. Clin Chem 1984;30:319-322)

Reference Values

Therapeutic concentration: 0.8-2.0 mcg/mL (trough value)

Toxic concentration: >2.0 mcg/mL (trough value)

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
MEX Mexiletine, S In Process


Result ID Test Result Name Result LOINC Value
9245 Mexiletine, S 3819-0

Reject Due To


Mild OK; Gross OK


Mild OK; Gross reject


Mild OK; Gross OK


Plasma, serum gel tube