Formulary
Mexiletine: Indications, Dosing, Side Effects and Interactions
Mexiletine is a sodium channel blocker with anti-arrhythmic and muscle relaxant properties.
MedNext Academy | 3 min read
Mexiletine: Indications, Dosing, Side Effects and Interactions
Mexiletine is a sodium channel blocker with anti-arrhythmic and muscle relaxant properties.
Drug action
Mexiletine is a sodium channel blocker with anti-arrhythmic and muscle relaxant properties.
Indications and dose
**Life-threatening ventricular arrhythmias (specialist use only)**
- **Adult** (By Mouth): Loading dose 400 mg, followed by maintenance 150-300 mg 2-3 times a day, dose may be adjusted if necessary in steps of 50 or 100 mg at intervals of at least 2 to 3 days, according to response and tolerance, at least 1 week is recommended between dose adjustments in patients who are poor CYP2D6 metabolisers; maximum 1200 mg per day.
**Myotonia in non-dystrophic myotonic disorders**
- **Adult** (By Mouth): 167 mg once daily for at least 1 week, then increased if necessary to 333 mg daily in divided doses for at least another week, then increased if necessary to 500 mg daily in divided doses; maintenance 167-500 mg daily; maximum 500 mg per day.
Cautions
General cautions: Epilepsy or history of seizures (increased risk of seizures); poor CYP2D6 metabolisers (increased plasma levels) Specific cautions: When used for myotonia Cardiac disorders other than those contra-indicated When used for ventricular arrhythmias Congestive heart failure; first-degree AV block or intraventricular conduction abnormalities; hypotension
Contraindications
When used for myotonia Abnormal Q-waves; atrial tachyarrhythmia, fibrillation, or flutter; complete heart block or any heart block susceptible to evolve to complete heart block; heart failure (with ejection fraction less than 50%); history of myocardial infarction; sinus node dysfunction; symptomatic coronary artery disease; ventricular tachyarrhythmia When used for ventricular arrhythmias Cardiogenic shock; inherited long QT syndrome (other than LQTS3); reduced left ventricular ejection fraction; severe AV conduction disturbances (unless pacemaker fitted); severe heart failure; sinus node dysfunction (unless pacemaker fitted)
Side effects
Common or very common Angina pectoris; arrhythmias; asthenia; ataxia; chest discomfort; constipation; dizziness; drowsiness; dry mouth; gastrointestinal discomfort; headache; hypotension; insomnia; malaise; nausea; pain in extremity; palpitations; paraesthesia; skin reactions; tinnitus; tremor; vasodilation; vertigo; vision disorders Uncommon Alopecia; arthralgia; erectile dysfunction; hiccups; loss of consciousness; memory loss; seizure; speech disorder Rare or very rare Agranulocytosis; heart failure; hepatic disorders; neutropenia; severe cutaneous adverse reactions (SCARs) Frequency not known Atrioventricular block; circulatory collapse; confusion; diarrhoea; gastrointestinal disorders; hallucination; leucopenia; lupus-like syndrome; pulmonary fibrosis; taste altered; thrombocytopenia; vomiting
Interactions
**Other interactions (16):**
- Ropivacaine hydrochloride should be used with caution in patients receiving other local anaesthetics or agents structurally related to amide-type local anaesthetics, e.g., certain antiarrhythmics,...
- Anti-arrhythmics: May delay the gastro-intestinal absorption of mexiletine or quinidine (which may also reduce the efficacy of codeine).
- Lidocaine should be used with caution in patients receiving other local anaesthetics or agents structurally related to amide-type local anaesthetics, e.g.
- Disopyramide Flecainide Systemic lidocaine Mexiletine Propafenone Interaction not studied with any of the components of Elvitegravir/Cobicistat/Emtricitabine/Tenofovir Alafenamide Gilead.
- Bupivacaine should be used with caution in patients receiving other local anaesthetics or agents structurally related to amide-type local anaesthetics, e.g.
- Examples of drugs or drug classes affected by rifampicin: Antiarrhythmics (e.g.
Pregnancy
Specialist sources indicate use with caution-limited human and animal data available.
Breast feeding
Specialist sources indicate use with caution-limited data show present in breast milk; monitor breast-fed infants for adverse reactions.
Hepatic impairment
Caution in mild or moderate impairment; avoid in severe impairment (limited information available). M Dose adjustments Any dose increase should only be made after at least 2 weeks of treatment in mild or moderate impairment. M
Renal impairment
Avoid in severe impairment (limited information available). M
Medicinal forms
Capsule
Clinical governance
**Author:** MedNext Clinical Team. **Clinical reviewer:** Dr Shameer Deen, MBBS, MS, MRCS. **Sources:** BNF, Indian Pharmacopoeia, CIMS India. **Correction:** Report errors at support@mednext.academy.
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