Mexiletine
MEXITIL
What it isOral class IB sodium channel blocker; ventricular arrhythmia and myotonia.
Why this oneIt is effective for non-dystrophic myotonia, where few oral agents work.
What limits itGI upset and tremor limit the dose. Proarrhythmia in structural heart disease; CYP2D6 substrate.
FDA-approved for
- ventricular arrhythmias (1985)
Off-label
- neuropathic pain
- myotonia
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Life-threatening ventricular arrhythmia | Adult | 200 mg q8h | 200–300 mg q8h (up to 400 mg q8h) | 1200 mg/day |
Titration Allow a minimum of 2–3 days between dose adjustments
Renal No adjustment needed (usual doses in renal failure)
Hepatic Severe liver disease may require lower doses; monitor closely
Instructions
- Take with food or antacid
- For rapid control: loading dose 400 mg, then 200 mg in 8 hours
- May convert to q12h schedule if controlled on ≤300 mg q8h (up to 450 mg q12h)
Contraindications
- Cardiogenic shock
- Preexisting second- or third-degree AV block (without a pacemaker)
Cautions
- Proarrhythmia; reserve for life-threatening ventricular arrhythmia
- Acute liver injury / abnormal LFTs
- Blood dyscrasias (agranulocytosis, thrombocytopenia, leukopenia)
- CNS effects: tremor, dizziness, coordination difficulty
- May worsen CHF in compromised ventricular function
Adverse reactions
- Upper GI distress: nausea/vomiting/heartburn
- Dizziness/lightheadedness
- Tremor
- Coordination difficulties
- Palpitations
- Nervousness
Pregnancy Undefined
Lactation Undefined
⚠ BOXED WARNING
- Increased mortality in asymptomatic PVCs
Cost, est. cash$10–$300/month
Generic entry1995
Classes and tags
Clinical profile
Legacy pregnancy categoryC
Defining liabilityProarrhythmia, conduction slowing and agent-specific organ toxicity; overdose may cause malignant dysrhythmia.
Mechanism of action: Mexiletine ballicule
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Memory aids: mascots and interaction avatars
QT shortening
