|Values are valid only on day of printing.|
Assessing achievement of optimal therapeutic concentrations
Assessing potential toxicity
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 at a rate of 10.3 mL/min/kg. Mexiletine has a volume of distribution of 9.5 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 occurs 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.
Therapeutic concentration: 0.8-2.0 mcg/mL (trough value)
Toxic concentration: >2.0 mcg/mL (trough value)
Optimal response to mexiletine occurs when the serum concentration is within the range of 0.8 to 2.0 mcg/mL (trough value).
No significant cautionary statements
1. Burtis CA, Ashwood ER, Bruns DE, et al: Tietz Textbook of Clinical Chemistry and Molecular Diagnosis (Fifth edition), Elsevier, St. Louis, USA, 2012
2. Joseph SP, Holt DW: Electrophysiological properties of mexiletine assessed with respect to plasma concentrations. Eur J Cardiol 1980;11:115-121