Contraindications and Precautions for Mexiletine Use

Absolute Contraindications

• The American Heart Association recommends that mexiletine is contraindicated in patients with severe sinus node dysfunction unless a pacemaker is present, and in patients with marked sinus bradycardia without pacemaker protection 1

Relative Contraindications and Cautions

Cardiac Conditions

• The American College of Cardiology suggests that mexiletine may exacerbate heart failure in susceptible patients, and caution is advised in patients with structural heart disease as it can potentially worsen arrhythmias 2
• Concomitant use with QT-prolonging medications requires careful consideration and monitoring, according to the American Heart Association 1

Hepatic Impairment

• Patients with severe liver disease may require dosage adjustment due to prolonged half-life of mexiletine (14-16 hours vs normal 10-14 hours) 2

Drug Interactions

• Combination with amiodarone requires careful monitoring due to potential additive effects on cardiac conduction, as recommended by the American Heart Association 1

Other Considerations

• Blood dyscrasias have been associated with mexiletine use in some patients, according to the American College of Cardiology 2

Monitoring Requirements

• ECG monitoring is essential during initiation of therapy, particularly when used in combination with other antiarrhythmic agents, as recommended by the American Heart Association 1

Common Adverse Effects to Monitor

• Neurological and cardiac adverse effects, such as tremor, ataxia, paresthesias, dizziness, and potential for AV block or worsening of arrhythmias, may occur in patients taking mexiletine, according to the American College of Cardiology 2

Mexiletine Contraindications and Precautions

Cardiac Conditions

• The American Heart Association recommends that mexiletine be used with caution in patients with heart failure, as it may exacerbate the condition in susceptible patients 3
• Mexiletine does not prolong QT intervals, unlike other sodium channel blockers used after myocardial infarction that increased mortality in the CAST trial, according to the European Society of Cardiology 4

Special Populations

• The American College of Cardiology suggests that mexiletine may be beneficial in patients with inherited long QT syndrome type 3 (LQT3) and may actually shorten the QTc 5, 4
• In long QT syndrome type 3, mexiletine, ranolazine, and flecainide have been used to reduce recurrent arrhythmias, as recommended by the American College of Cardiology 6, 5

Common Adverse Effects

• The American Heart Association notes that cardiac adverse effects, such as heart failure and AV block, can occur with mexiletine use 3