Mexiletine
Antiarrhythmics
Antiarrhythmics
An oral class IB antiarrhythmic, a cousin of lidocaine, for life-threatening ventricular arrhythmias. Nausea, tremor and dizziness are common.
Quick facts
- Group
- Antiarrhythmics
- Target
- Cardiac sodium channel Nav1.5
- Key effects
- Nausea · Tremor · Dizziness and lightheadedness
- Monitor
- ECG and rhythm · Liver tests
- ATC
- C01BB02
No doses: the clinician sets them by the current guideline.
Mechanism of action
Mexiletine is a local anaesthetic-type sodium channel blocker, structurally similar to lidocaine but active by mouth. Like other class IB drugs it binds and unbinds quickly and acts mostly on depolarised, rapidly firing or ischaemic ventricular tissue, suppressing ventricular ectopy, with little effect on normal conduction.
- Mexiletine blocks Nav1.5 sodium channels, binding and unbinding fast
- It acts mostly on depolarised or ischaemic ventricular tissue
- Ventricular ectopy and re-entry are suppressed
Indications
- Documented life-threatening ventricular arrhythmias such as sustained ventricular tachycardia Ventricular tachycardia →
Adverse effects
Common
- Nausea, vomiting and heartburn
- Tremor
- Dizziness and lightheadedness
- Incoordination and nervousness
Contraindications
- Cardiogenic shock
- Second- or third-degree AV block without a pacemaker
Key interactions
- Theophylline
- Higher theophylline levels; levels are monitored
- CYP2D6 or CYP1A2 inhibitors and inducers
- Changes in mexiletine levels
- Drugs or diets that markedly change urine pH
- Altered mexiletine elimination; avoided
What is monitored
- ECG and rhythm
- Liver tests
- Blood count if infection signs appear
Administration and safety
- Taken with food or an antacid to reduce stomach upset.
- For sustained ventricular tachycardia it is started in hospital, like other antiarrhythmics.
Pregnancy and breastfeeding
Animal studies showed no malformations, but human data are lacking; it is used in pregnancy only if clearly needed.
Nursing care
- Ask about nausea, tremor, dizziness or unsteady walking.
- Teach the patient to report fever, rash, yellow skin, sore throat or fainting.
- Watch the rhythm strip for new arrhythmias.
Pharmacokinetics
- Absorption
- Well absorbed by mouth with low first-pass metabolism, unlike lidocaine
- Metabolism
- Liver, by CYP2D6 and CYP1A2; liver disease prolongs its half-life
- Elimination
- Urine; marked changes in urine pH alter its excretion
Test yourself
Think of the answer, then tap the question to see it.
How is mexiletine related to lidocaine?
Both are class IB sodium channel blockers; mexiletine is similar in structure but active by mouth because its first-pass metabolism is low.
What are the most common adverse effects of mexiletine?
Nausea, vomiting and heartburn, tremor, dizziness and incoordination.
Which bronchodilator rises in the blood when given with mexiletine?
Theophylline.
Connections
← Back to the class: Antiarrhythmics
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - MEXILETINE HYDROCHLORIDE capsule (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.