mexiletine
Brand: Mexitil
Prototype: lidocaine-iv
Drug Class: antiarrhythmic (Class IB)
Drug Family: antiarrhythmic
Subclass: oral sodium channel blocker
Organ Systems: cardiovascularcns
Mechanism of Action
Oral Class IB analog of lidocaine; blocks inactivated sodium channels; reduced automaticity in ischemic tissue.
voltage-gated sodium channels (inactivated state)
Indications
- ventricular arrhythmias (sustained)
- neuropathic pain (off-label)
- myotonic dystrophy (off-label)
Contraindications
- cardiogenic shock
- 2nd/3rd degree AV block
- severe structural heart disease (relative)
Adverse Effects
Common
- GI upset (nausea, vomiting — take with food)
- tremor
- dizziness
- ataxia
Serious
- proarrhythmia
- hepatotoxicity
- severe CNS effects
Pharmacokinetics (ADME)
| Absorption | 85-90% oral |
| Distribution | moderate lipophilicity |
| Metabolism | extensive hepatic CYP2D6, CYP1A2 |
| Excretion | renal 10% unchanged |
| Half-life | 10-12 hours |
| Onset | 1.5-3 hours |
| Peak | 2-3 hours |
| Duration | 8-12 hours |
| Protein Binding | 70% |
| Vd | 5-12 L/kg |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| CYP1A2 inducers (smoking) | reduces mexiletine levels | moderate |
| amiodarone | increases mexiletine levels | moderate |
Nursing Considerations
- Take with food or antacids to reduce GI side effects
- Smoking (CYP1A2 induction) significantly reduces mexiletine levels — warn patients against smoking
- Monitor hepatic enzymes
Clinical Pearls
- Oral lidocaine analog — same mechanism, different route
- Smoking dramatically reduces effectiveness via CYP1A2 induction
Safety Profile
Pregnancy use-with-caution
Lactation use-with-caution
Renal Adjustment Not required
Hepatic Adjustment Required
TDM Not required
Concordance Terms
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