Mexiletine, Serum
Use
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. Optimal response to mexiletine occurs when the serum concentration is within the range of 0.5 to 2.0 mcg/mL (trough value).
Special Instructions
Specimens should only be collected after the patient has been receiving mexiletine for at least 3 days. Trough concentrations should be collected just before administration of the next dose. If not ordering electronically, complete, print, and send one of the following forms with the specimen: Cardiovascular Test Request (T724) or Therapeutics Test Request (T831).
Limitations
Mexiletine toxicity can occur at concentrations above 2.0 mcg/mL (trough value) and is characterized by symptoms such as nausea, hypotension, sinus bradycardia, paresthesia, seizures, intermittent left bundle branch block, and temporary asystole. Specimens obtained from gel tubes or anticoagulated collections can cause assay interference.
New York Approved
Methodology
Mass Spectrometry (LC-MS/MS)
Biomarkers
LOINC Codes
- 40779-1
- 40779-1
Result Turnaround Time
2-5 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1.5 mL
Minimum Volume
0.5 mL
Container
Red top (serum gel/SST are not acceptable)
Collection Instructions
Draw blood immediately before the next scheduled dose. Within 2 hours of collection, centrifuge and aliquot serum into a plastic vial.
Patient Preparation
Specimens should only be collected after the patient has been receiving mexiletine for at least 3 days. Trough concentrations should be collected just before administration of the next dose.
Causes for Rejection
Anticoagulated or gel tube collection
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 28 days |
| Refrigerated | 28 days |
| Frozen | 28 days |