|Trade names||Mexitil, NaMuscla, others|
|Main uses||Ventricular arrhythmias, myotonia|
|Side effects||Chest discomfort, headache, lightheadedness, nausea, arrhythmias, heart failure, liver problems|
|By mouth, intravenous|
|Onset of action||Within 2 hr|
|Typical dose||200 mg TID|
|Metabolism||Liver (CYP2D6 and 1A2-mediated)|
|Elimination half-life||10–12 hours|
|Chemical and physical data|
|Molar mass||179.263 g·mol−1|
|3D model (JSmol)|
Mexiletine, sold under the brand name Mexitil among others, is a medication used to treat ventricular arrhythmias that are life threatening and certain types of myotonia. It may be used when other treatments do not work. While it has been used for diabetic neuropathy such use is not well supported. It is taken by mouth.
Common side effects include chest discomfort, headache, lightheadedness, and nausea. Other side effects may include arrhythmias, heart failure, liver problems, low platelets, seizures, and low white blood cells. It is a class IB anti-arrhythmic and works as a sodium channel blocker.
Mexiletine was approved for medical use in 1985. It is available as a generic medication. In the United Kingdom 100 pills of 167 mg costs the NHS about £5,000 as of 2021. In the United States 100 pills of 150 mg costs about 47 USD.
In general when treating arrhythmias, mexiletine is reserved for use in dangerous heart rhythm disturbances such as ventricular tachycardia. It is of particular use when treating arrhythmias caused by long QT syndrome. The LQT3 form of long QT syndrome is amenable to treatment with mexiletine as this form is caused by defective sodium channels that continue to release a sustained current rather than fully inactivating, however other forms of long QT syndrome can also be treated with this medication.
Mexiletine has been used to treat chronic pain and may also be used to treat muscle stiffness resulting from myotonic dystrophy (Steinert's disease) or nondystrophic myotonias such as myotonia congenita (Thomsen syndrome or Becker syndrome).
Common side effects of mexiletine include abdominal pain, chest discomfort, drowsiness, headache, nausea and skin reactions. Uncommon or rare side effects include seizures and liver dysfunction.
Mexiletine is an oral analogue of lidocaine. It is a class IB antiarrhythmic which shorten the refractory period and action potential duration (APD). Decrease in APD more than that of ERP so there is increase ERP/APD ratio. The drug has a bioavailability of 90%, and peak plasma concentrations are seen after 2–4 hours. The mean drug half-life is approximately 11 hours.
Mexiletine is predominantly metabolised by the liver. The pharmacokinetics of mexiletine are preserved with even moderate to severe renal impairment, but dose adjustment may be required when creatinine clearance falls below 10 mL/minute.
Society and culture
Mexiletine is available for human use in the US, and has been reintroduced in the UK as a licensed product, having previously only been available as a 'named patient' import. The drug is sold under the trade name Mexitil for use in arrhythmias and NaMuscla for use in myotonia.
NaMuscla in the United Kingdom is sold by Lupin Healthcare UK.
Mexiletine is available to veterinarians in the US for the treatment of heart disease in dogs and cats.[medical citation needed] It is commonly used for the treatment of arrhythmogenic right ventricular cardiomyopathy (ARVC) in Boxer dogs in combination with sotalol.[medical citation needed]
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