Mexiletine

About Mexiletine

Mexiletine steadies the electrical activity of the heart’s lower chambers. The label approves it only for documented ventricular arrhythmias that the physician judges life-threatening, such as sustained ventricular tachycardia; treating lesser arrhythmias or symptom-free extra beats is not recommended, and safety and effectiveness in children have not been established. As with other drugs for life-threatening arrhythmias, treatment is started in the hospital. The usual start is 200 mg every eight hours, taken with food or an antacid, adjusted by 50 mg or 100 mg steps no more often than every two to three days. Most people need 200 mg to 300 mg every eight hours, and the maximum is 1200 mg a day. Someone controlled on 300 mg or less every eight hours may be switched to every 12 hours.

The boxed warning has two parts. First, in the Cardiac Arrhythmia Suppression Trial (CAST), two other antiarrhythmics, encainide and flecainide, raised the death rate in people with symptom-free arrhythmias after a heart attack; because mexiletine can also provoke arrhythmias, it is reserved for life-threatening ones. Second, abnormal liver tests have been reported, some in the first few weeks of treatment, mostly in people with heart failure or reduced blood flow, though a link to mexiletine has not been established; severe liver injury is described elsewhere on the label. Mexiletine must not be taken in cardiogenic shock or with second or third degree heart block unless a pacemaker is in place. Other warnings cover DRESS (a severe drug reaction with rash, fever and organ involvement), worsening arrhythmia, seizures, and rare drops in white blood cells or platelets. The most common side effects are nausea, vomiting and heartburn, dizziness or lightheadedness, tremor and trouble with coordination.

Response is checked with ECGs, and sometimes a Holter monitor, while the dose is adjusted. People with severe liver disease or marked right-sided heart failure may need lower doses and close follow-up; kidney failure does not usually change the dose. Diet matters more than with most drugs: changes that make the urine markedly more acidic or alkaline speed or slow its removal, and MedlinePlus advises telling the prescriber about a vegetarian diet or large amounts of citrus, cranberries, vegetables, meat or dairy. Tobacco may lower its effect. There are no adequate human studies in pregnancy, and mexiletine passes into breast milk at levels similar to the blood, so the label suggests considering an alternative to breastfeeding. It is not a controlled substance.

Taking Mexiletine

How to take it

Take each capsule with food or an antacid, at about the same times every day, usually every eight hours (or every 12 hours if the prescriber has switched you). Keep taking it even if you feel well, and do not stop without talking to the prescriber.

If you miss a dose

Take it as soon as you remember, unless it is almost time for the next dose; then skip the missed dose. Do not take a double dose.

Storage

In the original tightly closed, light-resistant container at room temperature, away from heat and moisture (not in the bathroom), out of reach of children.

Interactions to know about

Fluvoxamine and propafenone can raise mexiletine levels, and phenytoin, rifampin and phenobarbital can lower them. Mexiletine raises theophylline levels and slows the clearance of caffeine; cimetidine has had varying effects. Aluminum and magnesium antacids, opioid pain medicines and atropine slow its absorption, metoclopramide speeds it, and drugs or diets that strongly change urine acidity alter how fast it leaves the body.

This summarizes the official prescribing information. Your prescriber’s and pharmacist’s instructions, and the leaflet that comes with your medicine, take priority.

Why the cash price for Mexiletine differs from pharmacy to pharmacy

Mexiletine is an old generic, but it is a specialist heart drug that many pharmacies fill rarely, so a pharmacy may order a bottle in for one prescription. Quotes depend on which maker the pharmacy buys from, whether it stocks the strength prescribed, and whether the drug is on a flat-price generic list.

The dose is taken two or three times a day, so a month’s supply is a sizable count of capsules, and a dose built from two strengths means two items on the quote. Treatment is long term, so the dispensing fee on each fill adds up.

Ways to pay less for Mexiletine without insurance

• If the prescription names Mexitil, expect a generic; the brand is no longer sold in the US.
• Once the dose is stable, ask the prescriber whether a ninety-day supply is appropriate, so you pay fewer dispensing fees.
• Ask whether the pharmacy stocks your exact strength, and whether the prescriber can write the dose using a single capsule strength where that suits you.
• Compare more than one pharmacy, since stocking and supplier differ for a drug that is filled less often.
• Upload the prescription to Script Unlock so licensed pharmacies can quote their cash price. You pay the pharmacy directly.

Questions to ask your pharmacist about Mexiletine

1. 1.Should I take my mexiletine with meals or with an antacid, and does the antacid I use interfere with my other medicines?
2. 2.Do my theophylline, caffeine or smoking habits change how my mexiletine works?
3. 3.Which of my other medicines, such as fluvoxamine, phenytoin or rifampin, could change my mexiletine level?
4. 4.Which symptoms, like yellow skin, a rash with fever, or a new irregular heartbeat, mean I should call my doctor right away?

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