Class Ib antiarrhythmic / sodium channel blocker
Mexiletine
Brand names: Namuscla
Adult dose
Dose: Myotonia: 167mg PO TDS up to 333mg TDS. Arrhythmia: 200–400mg every 8h
Route: PO
Frequency: TDS
Clinical pearls
- Non-dystrophic myotonia; refractory ventricular arrhythmia
- Specialist initiation
Contraindications
- 2nd/3rd degree AV block
- Cardiogenic shock
- Severe heart failure
- Hypersensitivity
Side effects
- GI upset
- Tremor
- Dizziness
- Conduction disturbances
- Hepatotoxicity
- Allergic skin reactions
Interactions
- CYP1A2 inhibitors (raised levels)
- Other antiarrhythmics
- QT-prolonging drugs
Monitoring
- ECG
- LFTs
Reference: BNF; NICE; SmPC; https://bnf.nice.org.uk/drugs/mexiletine/. Verify against your local formulary and the latest BNF before prescribing.
Related
Curated clinical cross-links plus same-class fallbacks.
Calculators
- NYHA Heart Failure Classification · Heart Failure
- GRACE ACS Risk Score · Acute Coronary Syndrome
- MAGGIC Heart Failure Risk Score · Heart Failure
- WHO Functional Classification (Pulmonary Hypertension) · Pulmonary Hypertension
- Long QT Syndrome (Schwartz Score) · Channelopathy / Sudden Cardiac Death
- Corrected Sodium (Hyperglycaemia) · Electrolytes
Pathways
- Acute Heart Failure · ESC 2021 Heart Failure Guidelines; NICE NG106
- NSTEMI / Unstable Angina · ESC 2020 NSTEMI Guidelines; NICE NG185
- New-Onset Atrial Fibrillation · ESC 2020 AF Guidelines; NICE NG196
- Hypertensive Emergency · ESC/ESH 2018 Hypertension Guidelines; NICE NG136
- Bradycardia Management · Resuscitation Council UK ABCDE; ESC 2021 Pacing Guidelines
- Ventricular Tachycardia / Fibrillation · Resuscitation Council UK ACLS; ESC 2022 Ventricular Arrhythmia Guidelines