Mexiletine 200mg Capsules
WARNING: This drug is only to be used to treat certain types of abnormal heartbeats that may be deadly. It may cause severe and sometimes deadly side effects. If you have questions, talk with the doctor.Rarely, liver problems have happened with this drug. Sometimes these problems happened within the first few weeks of taking it. Most of the time, they happened in people with heart failure or certain other heart problems. It is not known if this drug led to these cases of liver problems. If you have any questions, talk with the doctor. @ COMMON USES: It is used to treat certain types of abnormal heartbeats.This drug may need to be started in a hospital where you will be closely watched. Talk with your doctor.
Drug Class
Antiarrhythmic
Pharmacologic Class
Class IB Antiarrhythmic
Pregnancy Category
Category C
FDA Approved
Jan 1985
DEA Schedule
Not Controlled
Overview
What is this medicine?
Mexiletine is a medication used to treat certain types of irregular heartbeats (ventricular arrhythmias). It works by stabilizing the electrical activity in your heart, helping it beat more regularly. It's often used when other treatments haven't worked or aren't suitable.
How to Use This Medicine
Taking Your Medication Correctly
To ensure you get the most benefit from your medication, follow these guidelines:
Take your medication exactly as directed by your doctor. Carefully read all the information provided with your prescription and follow the instructions closely.
Take your medication with food or an antacid to help minimize potential stomach upset.
Continue taking your medication as prescribed by your doctor or healthcare provider, even if you start to feel better. It's essential to complete the full treatment course as recommended.
Storing and Disposing of Your Medication
To maintain the effectiveness and safety of your medication:
Store your medication at room temperature, protected from light and moisture. Avoid storing it in a bathroom or other humid environment.
Keep your medication in a safe and secure location, out of the reach of children and pets.
Properly dispose of any unused or expired medication. Do not flush it down the toilet or pour it down the drain unless specifically instructed to do so by your pharmacist or healthcare provider. Check with your pharmacist for guidance on the best disposal methods, and consider participating in local drug take-back programs.
What to Do If You Miss a Dose
If you miss a dose of your medication:
Take the missed dose as soon as you remember.
However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule.
* Do not take two doses at the same time or take extra doses to make up for the missed one.
To ensure you get the most benefit from your medication, follow these guidelines:
Take your medication exactly as directed by your doctor. Carefully read all the information provided with your prescription and follow the instructions closely.
Take your medication with food or an antacid to help minimize potential stomach upset.
Continue taking your medication as prescribed by your doctor or healthcare provider, even if you start to feel better. It's essential to complete the full treatment course as recommended.
Storing and Disposing of Your Medication
To maintain the effectiveness and safety of your medication:
Store your medication at room temperature, protected from light and moisture. Avoid storing it in a bathroom or other humid environment.
Keep your medication in a safe and secure location, out of the reach of children and pets.
Properly dispose of any unused or expired medication. Do not flush it down the toilet or pour it down the drain unless specifically instructed to do so by your pharmacist or healthcare provider. Check with your pharmacist for guidance on the best disposal methods, and consider participating in local drug take-back programs.
What to Do If You Miss a Dose
If you miss a dose of your medication:
Take the missed dose as soon as you remember.
However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule.
* Do not take two doses at the same time or take extra doses to make up for the missed one.
Lifestyle & Tips
- Take mexiletine exactly as prescribed by your doctor. Do not stop taking it suddenly without consulting your doctor.
- Take mexiletine with food or an antacid to help reduce stomach upset (nausea, vomiting).
- Avoid grapefruit juice as it may affect how your body processes the medication.
- Report any new or worsening symptoms, especially dizziness, tremor, vision changes, or signs of a new irregular heartbeat.
- Limit or avoid alcohol consumption, as it can worsen side effects.
- Do not drive or operate machinery until you know how this medication affects you, as it can cause dizziness or blurred vision.
Available Forms & Alternatives
Available Strengths:
Dosing & Administration
Adult Dosing
Standard Dose:
200 mg orally every 8 hours after a loading dose of 400 mg, followed by 200 mg in 8 hours.
Dose Range:
600 - 1200 mg
Condition-Specific Dosing:
ventriculararrhythmias:
Initial loading dose of 400 mg, followed by 200 mg in 8 hours, then 200 mg every 8 hours. May adjust dose by 50-100 mg increments every 2-3 days. Max 1200 mg/day.
Pediatric Dosing
Neonatal:
Not established (limited off-label use for specific channelopathies)
Infant:
Not established (limited off-label use for specific channelopathies)
Child:
Not established (limited off-label use for specific channelopathies, e.g., 1.4-5 mg/kg/dose every 8 hours)
Adolescent:
Not established (limited off-label use for specific channelopathies)
Dose Adjustments
Renal Impairment:
Mild:
No specific adjustment needed
Moderate:
No specific adjustment needed
Severe:
Consider dose reduction (e.g., 25-50% reduction) if CrCl < 10 mL/min, monitor closely.
Dialysis:
Mexiletine is not significantly removed by hemodialysis. Dose adjustment may be needed based on clinical response and adverse effects.
Hepatic Impairment:
Mild:
Consider lower initial doses and slower titration.
Moderate:
Significant dose reduction (e.g., 50% reduction) and careful monitoring required.
Severe:
Contraindicated or significant dose reduction (e.g., 75% reduction) and extreme caution; monitor plasma levels if possible.
Pharmacology
Mechanism of Action
Mexiletine is a Class IB antiarrhythmic agent that exerts its electrophysiologic effect by blocking the fast inward sodium current in myocardial cells. This action reduces the rate of rise of the action potential (Vmax) and decreases the effective refractory period and action potential duration, particularly in ischemic tissue. It has little or no effect on repolarization or conduction velocity in normal myocardial tissue.
Pharmacokinetics
Absorption:
Bioavailability:
90%
Tmax:
2-3 hours
FoodEffect:
Food delays the rate of absorption but does not significantly affect the extent of absorption. Administer with food or antacids to minimize GI upset.
Distribution:
Vd:
5-7 L/kg
ProteinBinding:
50-60%
CnssPenetration:
Yes
Elimination:
HalfLife:
10-12 hours (range 6-17 hours)
Clearance:
Not available (highly variable)
ExcretionRoute:
Primarily hepatic metabolism with subsequent renal excretion of metabolites; minor renal excretion of unchanged drug.
Unchanged:
<10%
Pharmacodynamics
OnsetOfAction:
Within 30 minutes to 2 hours (oral)
PeakEffect:
2-3 hours
DurationOfAction:
8-12 hours
Safety & Warnings
BLACK BOX WARNING
In the National Heart, Lung, and Blood Institute's Cardiac Arrhythmia Suppression Trial (CAST), a long-term, multicenter, randomized, double-blind study in patients with asymptomatic non-life-threatening ventricular arrhythmias who had a myocardial infarction more than six days but less than two years previously, an excess mortality or nonfatal cardiac arrest rate was seen in patients treated with encainide or flecainide (Class IC antiarrhythmics) compared with that seen in patients assigned to placebo. The findings of the CAST study are not directly applicable to mexiletine, but given the similar electrophysiologic effects of Class I antiarrhythmics, the risk of proarrhythmia should be considered.
Side Effects
Serious Side Effects: Seek Medical Help Immediately
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you experience any of the following symptoms, contact your doctor or seek medical attention right away:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of liver problems, including:
+ Dark urine
+ Tiredness
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Vomiting
+ Yellow skin or eyes
Shakiness
Changes in eyesight
Chest pain
Severe dizziness or fainting
Abnormal heartbeat (new or worsening)
Seizures
Changes in balance
Swollen glands
Urination problems (inability to pass urine or changes in urine output)
Muscle pain or weakness
Unexplained bruising or bleeding
Signs of infection, such as fever, chills, or sore throat
Feeling extremely tired or weak
Rarely, this medication can cause low blood cell counts. If you experience any of the above symptoms, contact your doctor immediately.
If you have heart failure, be aware that this medication can worsen your condition. Contact your doctor if you experience:
Shortness of breath
Significant weight gain
Swelling in the arms or legs
Other Possible Side Effects
Most people taking this medication do not experience serious side effects, and some may not have any side effects at all. However, if you experience any of the following side effects, contact your doctor or seek medical attention if they bother you or do not go away:
Feeling nervous or excitable
Dizziness, tiredness, or weakness
Heartburn
Upset stomach or vomiting
Headache
Trouble sleeping
This is not a comprehensive list of all possible side effects. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you experience any of the following symptoms, contact your doctor or seek medical attention right away:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of liver problems, including:
+ Dark urine
+ Tiredness
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Vomiting
+ Yellow skin or eyes
Shakiness
Changes in eyesight
Chest pain
Severe dizziness or fainting
Abnormal heartbeat (new or worsening)
Seizures
Changes in balance
Swollen glands
Urination problems (inability to pass urine or changes in urine output)
Muscle pain or weakness
Unexplained bruising or bleeding
Signs of infection, such as fever, chills, or sore throat
Feeling extremely tired or weak
Rarely, this medication can cause low blood cell counts. If you experience any of the above symptoms, contact your doctor immediately.
If you have heart failure, be aware that this medication can worsen your condition. Contact your doctor if you experience:
Shortness of breath
Significant weight gain
Swelling in the arms or legs
Other Possible Side Effects
Most people taking this medication do not experience serious side effects, and some may not have any side effects at all. However, if you experience any of the following side effects, contact your doctor or seek medical attention if they bother you or do not go away:
Feeling nervous or excitable
Dizziness, tiredness, or weakness
Heartburn
Upset stomach or vomiting
Headache
Trouble sleeping
This is not a comprehensive list of all possible side effects. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- Severe dizziness or lightheadedness
- Fainting spells
- New or worsening palpitations (feeling your heart pound or skip a beat)
- Chest pain
- Shortness of breath
- Unusual bleeding or bruising
- Yellowing of the skin or eyes (jaundice)
- Dark urine or pale stools
- Persistent nausea, vomiting, or loss of appetite
- Tremors that are severe or interfere with daily activities
- Seizures
- Blurred vision or double vision
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced.
If you have heart block, a condition where the electrical signals between your heart's chambers are delayed or blocked.
This list is not exhaustive, and it is crucial to discuss all your medications (prescription, over-the-counter, natural products, and vitamins) and health issues with your doctor and pharmacist. They will help determine if it is safe to take this medication with your other medications and health conditions.
Remember, do not start, stop, or adjust the dose of any medication without first consulting your doctor. This will help ensure your safety and the effectiveness of your treatment.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced.
If you have heart block, a condition where the electrical signals between your heart's chambers are delayed or blocked.
This list is not exhaustive, and it is crucial to discuss all your medications (prescription, over-the-counter, natural products, and vitamins) and health issues with your doctor and pharmacist. They will help determine if it is safe to take this medication with your other medications and health conditions.
Remember, do not start, stop, or adjust the dose of any medication without first consulting your doctor. This will help ensure your safety and the effectiveness of your treatment.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. Regular blood work and laboratory tests should be conducted as directed by your doctor to monitor your condition.
A severe and potentially life-threatening reaction may occur, characterized by symptoms such as fever, rash, or swollen glands, accompanied by problems in various organs, including the liver, kidney, blood, heart, muscles and joints, or lungs. If you have any questions or concerns, consult your doctor for guidance.
If you are pregnant, planning to become pregnant, or are breastfeeding, notify your doctor. You and your doctor will need to discuss the potential benefits and risks of this medication to both you and your baby to make an informed decision.
A severe and potentially life-threatening reaction may occur, characterized by symptoms such as fever, rash, or swollen glands, accompanied by problems in various organs, including the liver, kidney, blood, heart, muscles and joints, or lungs. If you have any questions or concerns, consult your doctor for guidance.
If you are pregnant, planning to become pregnant, or are breastfeeding, notify your doctor. You and your doctor will need to discuss the potential benefits and risks of this medication to both you and your baby to make an informed decision.
Overdose Information
Overdose Symptoms:
- Severe nausea and vomiting
- Dizziness
- Ataxia (loss of coordination)
- Nystagmus (involuntary eye movements)
- Hypotension (low blood pressure)
- Bradycardia (slow heart rate)
- Seizures
- Coma
- Respiratory depression
- Cardiac arrest
What to Do:
If you suspect an overdose, seek immediate medical attention or call your local poison control center (e.g., 1-800-222-1222 in the US). Do not induce vomiting unless instructed by a healthcare professional.
Drug Interactions
Major Interactions
- CYP2D6 inhibitors (e.g., quinidine, fluoxetine, paroxetine): May significantly increase mexiletine plasma concentrations, increasing risk of toxicity.
- CYP1A2 inhibitors (e.g., cimetidine, fluvoxamine): May increase mexiletine plasma concentrations.
- Phenytoin: May decrease mexiletine plasma concentrations due to CYP induction.
- Rifampin: May decrease mexiletine plasma concentrations due to CYP induction.
- Opioids (e.g., morphine, codeine): May delay gastric emptying, affecting mexiletine absorption.
Moderate Interactions
- Antacids (e.g., aluminum hydroxide, magnesium hydroxide): May delay or decrease mexiletine absorption.
- Atropine and other anticholinergics: May delay gastric emptying, affecting mexiletine absorption.
- Drugs that alter urine pH (e.g., ammonium chloride, sodium bicarbonate): Acidification of urine increases renal excretion of mexiletine; alkalinization decreases it.
- Theophylline: Mexiletine may increase theophylline plasma concentrations, requiring dose adjustment of theophylline.
Monitoring
Baseline Monitoring
Electrocardiogram (ECG)
Rationale: To assess baseline cardiac rhythm, PR, QRS, and QT intervals, and identify any pre-existing conduction abnormalities.
Timing: Prior to initiation of therapy
Serum Electrolytes (Potassium, Magnesium)
Rationale: Electrolyte imbalances (hypokalemia, hypomagnesemia) can exacerbate arrhythmias and reduce antiarrhythmic efficacy.
Timing: Prior to initiation of therapy
Liver Function Tests (LFTs)
Rationale: Mexiletine is extensively metabolized by the liver; baseline assessment is crucial, especially in patients with hepatic impairment.
Timing: Prior to initiation of therapy
Renal Function Tests (Creatinine, BUN)
Rationale: To assess kidney function, as a small portion of the drug is renally excreted and metabolites are renally cleared.
Timing: Prior to initiation of therapy
Routine Monitoring
Electrocardiogram (ECG)
Frequency: Periodically, or with dose changes/symptom changes
Target: No significant prolongation of PR, QRS, or QT intervals; absence of proarrhythmia.
Action Threshold: Significant QRS widening (>25% of baseline), new arrhythmias, or signs of proarrhythmia warrant dose reduction or discontinuation.
Serum Electrolytes (Potassium, Magnesium)
Frequency: Periodically, especially if on diuretics or with GI upset
Target: Potassium 3.5-5.0 mEq/L, Magnesium 1.7-2.2 mg/dL
Action Threshold: Correct imbalances promptly.
Liver Function Tests (LFTs)
Frequency: Periodically, or if symptoms of hepatic dysfunction occur
Target: Within normal limits
Action Threshold: Significant elevation warrants dose reduction or discontinuation.
Blood Pressure and Heart Rate
Frequency: Regularly
Target: Within patient's normal range
Action Threshold: Significant hypotension or bradycardia.
Mexiletine Plasma Concentrations (Therapeutic Drug Monitoring)
Frequency: If clinical response is inadequate, toxicity is suspected, or in patients with renal/hepatic impairment or significant drug interactions.
Target: 0.7-2.0 mcg/mL
Action Threshold: Levels >2.0 mcg/mL are associated with increased risk of CNS and GI adverse effects; levels <0.7 mcg/mL may indicate subtherapeutic dosing.
Symptom Monitoring
- Dizziness
- Tremor
- Nausea
- Vomiting
- Ataxia
- Blurred vision
- Nystagmus
- Confusion
- Seizures
- Signs of new or worsening arrhythmias (palpitations, chest pain, shortness of breath, syncope)
- Signs of liver dysfunction (jaundice, dark urine, persistent nausea/vomiting)
Special Patient Groups
Pregnancy
Category C. Mexiletine crosses the placenta. Use only if the potential benefit justifies the potential risk to the fetus. Limited human data suggest no increased risk of major birth defects, but animal studies show adverse effects at high doses.
Trimester-Specific Risks:
First Trimester:
Potential for fetal exposure; risk of teratogenicity not clearly established in humans.
Second Trimester:
Continued fetal exposure; monitor maternal cardiac status and fetal well-being.
Third Trimester:
Continued fetal exposure; potential for neonatal effects (e.g., bradycardia) if exposed near term.
Lactation
Mexiletine is excreted into breast milk. The relative infant dose (RID) can be high (10-20%). The American Academy of Pediatrics considers it compatible with breastfeeding, but caution is advised. Monitor breastfed infant for adverse effects.
Infant Risk:
Moderate risk. Monitor infant for bradycardia, vomiting, sedation, or other signs of toxicity. Consider alternative if infant is premature or has underlying cardiac issues.
Pediatric Use
Not FDA approved for pediatric use. Used off-label for certain inherited channelopathies (e.g., long QT syndrome type 3, myotonia congenita) where its sodium channel blocking properties are beneficial. Dosing must be individualized and carefully monitored due to limited data and potential for serious adverse effects.
Geriatric Use
Elderly patients may have reduced hepatic clearance and increased half-life of mexiletine, leading to higher plasma concentrations and increased risk of adverse effects (especially CNS and GI). Start with lower doses and titrate slowly, monitoring closely for toxicity.
Clinical Information
Clinical Pearls
- Mexiletine is a Class IB antiarrhythmic, primarily used for ventricular arrhythmias, especially in patients with structural heart disease where other agents might be contraindicated.
- It is often used in combination with other antiarrhythmics (e.g., amiodarone) to enhance efficacy or reduce side effects.
- The most common side effects are GI (nausea, vomiting, heartburn) and CNS (dizziness, tremor, ataxia). Taking with food or antacids can mitigate GI upset.
- Due to its extensive hepatic metabolism, significant dose adjustments are required in patients with liver impairment.
- Monitor for proarrhythmic effects, especially in patients with pre-existing heart disease or electrolyte imbalances.
- Therapeutic drug monitoring (TDM) can be useful, especially in cases of suspected toxicity, non-response, or in patients with altered pharmacokinetics (e.g., liver disease, drug interactions).
Alternative Therapies
- Amiodarone (Class III antiarrhythmic)
- Lidocaine (IV, Class IB antiarrhythmic, for acute ventricular arrhythmias)
- Flecainide (Class IC antiarrhythmic)
- Propafenone (Class IC antiarrhythmic)
- Sotalol (Class III and beta-blocker)
- Dofetilide (Class III antiarrhythmic)
- Catheter ablation (non-pharmacological)
Cost & Coverage
Average Cost:
$50 - $200 per 30 capsules (200mg)
Generic Available:
Yes
Insurance Coverage:
Tier 1 or 2 (Generic)
General Drug Facts
If your symptoms or health issues persist or worsen, it is essential to contact your doctor promptly. To ensure safe and effective treatment, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so it's a good idea to check with your pharmacist for more information. If you have any questions or concerns about this medication, don't hesitate to discuss them with your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When seeking help, be prepared to provide details about the medication taken, the amount, and the time it happened.