Mexiletine for Dogs

Mexiletine happens to be a common antiarrhythmic drug administered orally to dogs suffering from chronic ventricular arrhythmia or irregular heartbeat. This antiarrhythmic medication is generally used to treat abnormal or irregular heart rhythms in canines, particularly ventricular arrhythmias like tachycardia. A Class 1B sodium channel blocker, the action mechanism of Mexiletine is very much akin to Lidocaine.

Therefore if your dog responds well to Lidocaine during a severe episode, the chances are that Mexiletine will also work effectively. Mexiletine is usually used together with amiodarone, sotalol, atenolol, and procainamide for dealing with and managing chronic ventricular arrhythmia. Hence vets recommend using sotalol or atenolol alongside Mexiletine, especially when monotherapy does not work.

Mexiletine has also been effective in alleviating symptoms of hereditary cardiomyopathy in Boxers and dilated cardiomyopathy in Dobermans. A dog is said to be responding well to Mexiletine if the medication helps reduce premature ventricular contractions by 85%.     

Mexiletine at a Glance

Brand Name


Generic Name



Class 1B antiarrhythmic drug

FDA certification


Availability (off-the-counter or as prescription)

Only on prescription

Suitable for


Dosage availability

Available as 150mg, 20omg, and 250mg capsules


Is Mexiletine Safe for Your Pet Dog?

Despite being a prescription drug, research and studies pinpoint that Mexiletine is, for the most part, safe for dogs. However, you should not administer the medication to your pet dog until and unless a vet has prescribed the drug. Mexiletine is not known to cause any severe side effects when offered to dogs to treat ventricular arrhythmia.

Vets usually prescribe an extremely low dosage of the medication to minimize the likelihood of acute side effects. Mexiletine is a costly drug and not readily available as the medicine's use by humans has decreased over time.   

Mexiletine for Dogs: How Does the Medication Work?

Mexiletine slows down electrical impulses in the canine's cardiac chambers, which reduces the sensitiveness of cardiac muscle cells to stimulation. At the same time, the drug helps maintain the average heart rate and overall cardiac muscle relaxations and contractions, unlike most antiarrhythmic medicines. This drug is generally used as an 'extra-label' or 'off-label' medication implying that its application is not always in strict conformity with the standard labelling.

However, as long as the medication's use does not contravene criteria stipulated by FDA and AMDUCA, its extra-label applications are legal. You should strictly abide by the directions (suggested by your vet) that could significantly vary from label directions.

Dosage and How to Administer the Drug

The dosage usually prescribed by vets is 5-10mg/kg, depending on the dog's weight, and administered three times daily. Mexiletine of a different formulation is generally prescribed for smaller dog breeds to minimize adverse effects resulting from a drug overdose. The medicine is usually administered orally in a capsule form though the drug is also available in liquid form.

You should give the medication and food to prevent or reduce the chances of nausea and vomiting. Mexiletine starts taking effect within a couple of hours, but the results are not evident or noticeable.    

What if You Miss a Dose?

If you forget to offer a dose, give it as soon as you remember, provided you recall within 5-10 minutes. On the other hand, if you remember having missed a dose just when it's time for the next dose, it's better to skip it. Always try to maintain a minimum time gap of 8 hours between one dose and the next to avoid overdosing.

Mexiletine: Common Side Effects

Drug Contraindications

Ensure to tell the vet about your pet's past or existing health issues (if any) and also about drugs you might be administering. You should administer Mexiletine to your dog with extreme care if the animal has any of the following health issues:-

  • Hypotension (low blood pressure)
  • Seizure disorder
  • Acute myocardial infarction
  • Liver dysfunction
  • Congestive heart failure
  • Second or third-degree atrioventricular (AV) heart block

Also, do not give Mexiletine if your dog is pregnant or allergic to the drug. Mexiletine may interact with drugs like opiates, primidone, rifampin, griseofulvin, Phenobarbital, antacids, and urinary acidifiers. 

Disclaimer: The above content is based on multiple research articles referred to online. Global Dog Breeds intends to share information, but it's strictly advised to consult a veterinarian and seek advice before using any medications described. We believe each condition and dog is unique, and only after careful evaluation from a qualified professional should you be offering any medications to your pet.

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