Antiarrhythmic drugs: Mexiletine (Class 1B)

Introduction

Mexiletine is an orally active antiarrhythmic agent, classified in subgroup 1B, similar to lidocaine. It is predominantly used for treating ventricular arrhythmias and has proven effective in alleviating chronic pain. This exploration focuses on mexiletine’s electrophysiologic actions, adverse effects, and therapeutic applications.

Electrophysiologic Actions

• Similar to Lidocaine: Mexiletine’s electrophysiologic and antiarrhythmic actions are similar to those of lidocaine. It blocks sodium channels and selectively depresses conduction in depolarized cells.
• Oral Administration: Unlike lidocaine, which is administered intravenously, mexiletine is orally active.

Pharmacokinetics

• Elimination Half-Life: Mexiletine has a longer half-life than lidocaine, ranging from 8 to 20 hours.
• Dosage: The usual daily dosage for treating ventricular arrhythmias is between 600 and 1200 mg, administered two or three times per day.

Adverse Effects

• Neurologic Effects: Mexiletine frequently causes dose-related neurologic adverse effects, including tremor, blurred vision, and lethargy.
• Gastrointestinal Effects: Nausea is also a common side effect.

Therapeutic Uses

• Ventricular Arrhythmias: Mexiletine is primarily used to treat ventricular arrhythmias.
• Chronic Pain: It has also shown significant efficacy in relieving chronic pain, especially pain due to diabetic neuropathy and nerve injury. The usual dosage for this off-label application is 450–750 mg/d orally.

Conclusion

Mexiletine is a versatile antiarrhythmic agent with a mechanism of action similar to that of lidocaine. Its longer half-life allows for oral administration, making it more convenient for long-term treatment. However, it does come with its own set of adverse effects, predominantly neurologic, which require careful monitoring. In addition to its primary use in treating ventricular arrhythmias, mexiletine has also found off-label use in managing chronic pain conditions. Like all medications, its use should be tailored to the individual patient’s needs and monitored for potential adverse effects.

Note: This article is intended for educational purposes and should not be considered as medical advice. Always consult with a healthcare professional for medical advice and treatment.