Classifications: antiarrhythmic, class ib;
Therapeutic: antiarrhythmic, class ib

Prototype: Lidocaine
Pregnancy Category: C


150 mg, 200 mg, 250 mg capsules


Analog of lidocaine with class IB electrophysiologic properties similar to those of procainamide. Shortens action potential refractory period duration and improves resting potential. Has little or no effect on atrial tissue and produces modest suppression of sinus node automatically and AV nodal conduction. Prolongs the His-to-ventricular interval (HQ) only if patient has preexisting conduction disturbance.

Therapeutic Effect

Has antiarrhythmic properties for ventricular disturbances.


Acute and chronic ventricular arrhythmias; prevention of recurrent cardiac arrests; suppression of PVCs due to ventricular tachyarrhythmias.

Unlabeled Uses

Wolff-Parkinson-White syndrome and supraventricular arrhythmias.


Severe left ventricular failure, cardiogenic shock, severe bradyarrhythmias. Preexisting second- or third-degree heart block; cardiogenic shock; pregnancy (category C); concurrent administration of drugs which alter urinary pH.

Cautious Use

Patients with sinus node conduction irregularities, intraventricular conduction abnormalities; hypotension; severe congestive heart failure; renal failure; liver dysfunction.

Route & Dosage

Ventricular Arrhythmias
Adult: PO 200–300 mg q8h (max: 1200 mg/d)
Child: PO 1.4–5 mg/kg q8h


  • Give with food or milk to reduce gastric distress.

Adverse Effects (≥1%)

CNS: Dizziness, tremor, nervousness, incoordination, headache, blurred vision, paresthesias, numbness. CV: Exacerbated arrhythmias, palpitations, chest pain, syncope, hypotension. GI: Nausea, vomiting, heartburn, diarrhea, constipation, dry mouth, abdominal pain. Skin: Rash. Body as a Whole: Dyspnea, edema, arthralgia, fever, malaise, hiccups. Urogenital: Impotence, urinary retention.


Drug: Phenytoin, phenobarbital, rifampin may decrease mexiletine levels; cimetidine, fluvoxamine may increase mexiletine levels; may increase theophylline levels; may increase proarrhythmic effects of dofetilide (separate administration by at least 1 wk).


Absorption: Readily from GI tract. Peak: 2–3 h. Distribution: Distributed into breast milk. Metabolism: In liver. Elimination: In urine; renal elimination increases with urinary acidification. Half-Life: 10–12 h.

Nursing Implications

Assessment & Drug Effects

  • Check pulse and BP before administration; make sure both are stabilized.
  • Effective serum concentration range is 0.5–2 mcg/mL.
  • Lab tests: Baseline and periodic liver function tests.
  • Supervise ambulation in the weak, debilitated patient or the older adult during drug stabilization period. CNS adverse reactions predominate (e.g., intention tremors, nystagmus, blurred vision, dizziness, ataxia, confusion, nausea).
  • Encourage drug compliance; affected particularly by the distressing adverse effects of tremor, ataxia, and eye symptoms.
  • Check frequently with patient about adherence to drug regimen. If adverse effects are increasing, consult physician. Dose adjustment or discontinuation may be needed.

Patient & Family Education

  • Learn about pulse parameters to be reported: Changes in rhythm and rate (bradycardia = pulse below 60); symptomatic bradycardia (light-headedness, syncope, dizziness), and postural hypotension.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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