治療心律不整 Prevention and treatment of ventricular arrhythmia.

Class Ib Antiarrhythmic Agent
Mexiletine hydrochloride can reduce VPCs, paired VPCs, and nonsustained ventricular tachycardia and can suppress the recurrence of ventricular tachycardia and/or fibrillation in patients with ventricular tachycardia and/or fibrillation.

Absorption:
1. Well absorbed
2. Bioavailability: 90%
3. Onset of action: 30 to 120 minutes (with loading regimen)
4. Time to peak, serum: 2 to 3 hours
Distribution:
1. Vd: 5 to 7 L/kg
2. Protein binding: 50% to 60%
Metabolism:
1. Hepatic via CYP2D6 metabolism to inactive metabolites (~90%) and major metabolites p-hydroxymexiletine, hydroxy-methylmexiletine, and N-hydroxy-mexiletine (minimal antiarrhythmic activity)
2. Low first-pass effect
Excretion:
Urine (10% as unchanged drug); urinary acidification increases excretion, alkalinization decreases excretion
Half-life elimination:
1. General: ~10 to 12 hours
2. Severe renal impairment (CrCl <10ml/min): ~ 15 hours
3. Moderate to severe hepatic impairment: ~ 25 hours

1. Sinus node dysfunction
2. Conduction defect
3. Bradycardia, hypotension
4. Cardiac, renal or hepatic failure

C

Safe; milk/plasma ratio varied form 0.78 to 2.0. One case found difficult feeding in nursing infant.

Nausea, vomiting, indigestion, unpleasant taste, hiccups, lightheadedness, drowsiness, confusion, dizziness, diplopia, blurred vision, nystagmus, dysarthria, ataxia, tremor, paraesthesia, convulsions, sinus bradycardia, hypotension, atrial fibrillation, palpitations.

Initial dose: 150-200 mg every 8 to 12 hours (may load with 400 mg if necessary)
Maintenance dose: 400-800 mg/day in divided dose, starting 2-6 hrs after the loading dose

No dosage adjustment necessary.

There are no dosage adjustments provided in the manufacturer's labeling.
Patients with hepatic impairment or hepatic congestion secondary to heart failure may require dose reduction (half-life is approximately doubled in patients with hepatic impairment).