Mexiletine

Mexiletine.svg

Mexiletine is a medication used to treat certain types of serious ventricular arrhythmias (abnormal heart rhythms). It is classified as a Class IB antiarrhythmic agent and is chemically related to lidocaine. Mexiletine works by blocking sodium channels in the heart, which helps to stabilize the cardiac cell membrane and reduce abnormal electrical activity.

Medical Uses

Mexiletine is primarily used to manage ventricular tachycardia and ventricular fibrillation, which are life-threatening conditions. It is also sometimes used off-label for the treatment of neuropathic pain and myotonia in patients with certain types of muscular dystrophy.

Mechanism of Action

Mexiletine exerts its effects by inhibiting the influx of sodium ions through the sodium channels during the depolarization phase of the cardiac action potential. This action helps to stabilize the cardiac cell membrane and reduce the excitability of the heart muscle, thereby preventing abnormal electrical activity that can lead to arrhythmias.

Pharmacokinetics

Mexiletine is well-absorbed from the gastrointestinal tract and has a bioavailability of approximately 90%. It is metabolized in the liver by the cytochrome P450 enzyme system, primarily by CYP2D6. The drug has a half-life of about 10-12 hours, allowing for twice or three times daily dosing.

Side Effects

Common side effects of mexiletine include nausea, vomiting, heartburn, and dizziness. Serious side effects can include liver toxicity, blood dyscrasias, and seizures. Patients taking mexiletine should be monitored regularly for signs of toxicity and adverse reactions.

Contraindications

Mexiletine is contraindicated in patients with cardiogenic shock, second- or third-degree heart block (without a pacemaker), and known hypersensitivity to the drug. Caution is advised in patients with liver disease, renal impairment, and congestive heart failure.

Drug Interactions

Mexiletine can interact with other medications, including beta-blockers, phenytoin, and theophylline. These interactions can either increase the risk of side effects or reduce the effectiveness of mexiletine.

History

Mexiletine was first synthesized in the 1970s and was approved for medical use in the United States in 1985. It has since become an important medication in the management of life-threatening ventricular arrhythmias.

See Also

• Antiarrhythmic agent
• Ventricular arrhythmia
• Lidocaine
• Sodium channel blocker

External Links

Mexiletine