Mexiletine (Mexitil and others)

How Medicare covers it

Part D (forms used at home). Part A during a covered inpatient stay. No Part B clinician-administered form in the CMS Part B spending file.

What it treats

Mexiletine treats documented ventricular arrhythmias — dangerous fast heart rhythms that start in the lower chambers of the heart — such as sustained ventricular tachycardia, when a doctor judges them to be life-threatening. The label says it should not be used for lesser rhythm problems, and treatment of symptom-free early beats should be avoided.

What it is for, in depth

Mexiletine hydrochloride capsules are prescribed for documented ventricular arrhythmias, such as sustained ventricular tachycardia, that the treating doctor judges to be life-threatening. These are fast, dangerous rhythms coming from the ventricles, the heart's lower pumping chambers, and mexiletine is used only when the rhythm problem is serious enough to justify its risks — the label advises against using it for lesser arrhythmias and says people with symptom-free premature ventricular beats should not be treated with it. Starting treatment, like starting other drugs for life-threatening rhythms, should be done in the hospital so the heart rhythm can be watched closely. It comes as 150 mg, 200 mg, and 250 mg capsules, and it sits in the treatment path as a targeted antiarrhythmic for patients whose dangerous ventricular rhythm needs ongoing oral control.

How it works

Mexiletine is a Class 1B antiarrhythmic, similar to lidocaine but taken by mouth. It blocks the inward sodium current in heart cells, which slows the rise of the electrical signal and helps steady the heart rhythm.

How it is taken

It comes as capsules (150 mg, 200 mg, and 250 mg) taken by mouth, usually starting at 200 mg every 8 hours, taken with food or an antacid. The dose is adjusted slowly, no more often than every 2 to 3 days, and treatment is usually started in the hospital.

Common side effects

Common side effects include nausea, vomiting, and heartburn or stomach upset, lightheadedness or dizziness, tremor (shaking), and trouble with coordination. Headache, blurred vision, nervousness, and numbness or tingling can also occur.

Serious warnings

Mexiletine can itself cause new or worse rhythm problems, so it is reserved for life-threatening arrhythmias. The label also reports abnormal liver function tests, sometimes in the first few weeks of treatment, and it must not be used in cardiogenic shock or in second- or third-degree heart block without a pacemaker.

Boxed warning

In the CAST study, patients with symptom-free, non-life-threatening rhythm problems after a heart attack who took similar antiarrhythmic drugs (encainide or flecainide) had a higher rate of death or non-fatal cardiac arrest (7.7%) than patients on placebo (3%). Because mexiletine can also cause rhythm problems and no antiarrhythmic drug has been shown to help people without life-threatening arrhythmias live longer, mexiletine should be reserved for patients with life-threatening ventricular arrhythmia. The boxed warning also notes reports of acute liver injury with abnormal liver tests, some in the first few weeks of therapy.

Who should be careful

People with liver disease may need lower doses and close monitoring, because the liver clears most of the drug. People with severe heart failure, a history of seizures, or existing heart block also need extra care, and blood levels should be watched when interacting drugs are added or stopped.

Major interactions

Drugs that block or speed up the liver enzymes CYP1A2 and CYP2D6 can raise or lower mexiletine levels — for example, fluvoxamine lowered its clearance, and enzyme inducers such as phenytoin, rifampin, and phenobarbital have lowered its levels. Mexiletine can raise theophylline levels, and it slows caffeine clearance, so your doctor may need to check blood levels when these are used together.

Cost and saving notes

If this drug is hard to afford on your Part D plan, you can ask the plan for a tier exception to move it to a lower cost tier, and your doctor can help explain why you need it. If you have limited income, Extra Help (the Part D Low-Income Subsidy) can lower premiums and drug costs, and you can apply through Social Security. Part D also has an annual out-of-pocket cap, so once your covered drug spending for the year reaches the cap, you pay nothing more for covered Part D drugs that year.

Why it is in its tier

Mexiletine (Mexitil and others) sits on Tier 3 in 51.61% of the plans that list it (1396 of 2705 listing plans). Tier 3 is the preferred brand tier — mid-level copays or coinsurance. The data-visible drivers: It is a generic product, and the CMS dashboard puts its average Part D spending at about $406 per beneficiary for 2024 — a relatively low-cost drug, which matches where plans place it. Only 49.23% of Part D plans list it at all, so many readers will find their plan does not list it and covers a similar drug instead. The tier shown is the most common one; individual plans vary.

Sources

• MEXILETINE HYDROCHLORIDE CAPSULE [AMERISYN LLC] — DailyMed
• MedlinePlus — National Library of Medicine
• MedlinePlus

What official patient guides say

In daily life, mexiletine is usually taken three times a day, every 8 hours, at about the same times each day, with food or an antacid to prevent stomach upset; once the rhythm is controlled, some people switch to twice a day, every 12 hours. Keep taking it even if you feel well and do not stop suddenly without talking to your doctor, because your condition may get worse. If you miss a dose, take it as soon as you remember unless it is almost time for the next dose — never take a double dose. Store it in its original container, tightly closed, at room temperature away from heat and moisture.

Source: MedlinePlus

Part D formulary coverage

Source: CMS Prescription Drug Plan Formulary, Pharmacy Network, and Pricing Information Files — Monthly file 2026-10-15 (plan year 2027), file 2027_20261008.zip (data.cms.gov dataset ed1496ea-23e7-41f1-9292-172fa842ccfb): basic drugs formulary file + plan information file, both dated 20261031 inside the zip; downloaded and aggregated 2026-10-30. Medication RxCUI sets resolved through the NLM RxNav (RxNorm) API.

What you pay

Without insurance, the cash benchmark is 0.24019 per unit (MEXILETINE 150 MG CAPSULE) — about nan for 30 units. NADAC benchmark — the average price pharmacies pay (CMS, as of 2026-11-04). Pharmacy shelf prices vary.

A tier is not a price; what you pay depends on your plan, pharmacy, and benefit stage; Extra Help or Medicaid can lower it further.

Sources: CMS Plan Benefit Package + formulary data; CMS NADAC · Checked 2026-11-07

Coverage by plan and tier

Of the 5,495 Medicare drug plans we track for 2027, 2,705 list Mexiletine (Mexitil and others) — 49.2% of plans. Most of those plans put it on Tier 3: 1,396 plans, 51.6% of the plans that list it. Other plans place it on Tier 2 (835 plans), Tier 4 (339 plans) or Tier 1 (135 plans). For example: CareSource MyCare Ohio (HMO D-SNP) puts it on Tier 1; Wellcare Simple Value (HMO-POS) puts it on Tier 3; Essence Advantage Select (HMO) puts it on Tier 3. You can compare these plans side by side on our Medicare Advantage hub. A tier is not a price. What you pay also depends on whether you have met your plan';s deductible, whether the drug costs a flat copay or a share of the price, and whether you get Extra Help or Medicaid.

Read next

• Part D in 2027: The $700 Deductible, the $2,400 Cap, and the $35 Insulin Rule
• Extra Help in 2027: Lower Drug Copays and Who Qualifies
• Checking Medicare Savings Programs and Extra Help

Part D spending averages (2024)

Source: CMS Medicare Part D Spending by Drug (Drug Spending Dashboard), release RY26 P04 V10, data through 2024 (DSD_PTD_RY26_P04_V10_DY24_BGM.csv), downloaded 2026-10-30

Companies covering this drug

Part D and Medicare Advantage plan sponsors that list this drug on a formulary, 50 at a time.