Procainamide

Mechanism of Action

• Class Ia
  • Binds to fast sodium channels in inactive state inhibiting recovery after repolarization
  • Prolongs action potential and reduces speed of impulse conduction
    • Depresses myocardial conduction
  • May act as negative inotrope, causing hypotension through peripheral vasodilation

Kinetics

• Onset of action: 5 - 10 minutes

Adult Dosing

• 20 - 50 mg/min intravenously over 25 - 30 minutes
• Give until:
  • arrhythmia is suppressed
  • patient develops hypotension
  • QRS segment prolongs by >50% of baseline
  • maximum dose of 17mg/kg is given
• If effective, start continuous infusion at 1-4 mg/min
  • Continuous infusion has fewer adverse effects than bolus

Indications

• Wide-complex tachycardia of unknown type (in patient with preserved left ventricular function)
• Stable ventricular tachycardia

Contraindications

• Not recommended for ventricular fibrillation or pulseless ventricular tachycardia, as it takes too long to dose
• 2nd or 3rd atrioventricular block
• Severe glycoside intoxication
• Prolonged QT segment
• Myasthenia gravis

Adverse Drug Reactions

• Myocardial depression
• Watch for QRS/QT segment prolongation, ventricular tachycardia, ventricular fibrillation, complete atrioventricular block, torsades de pointes

See Also

• Antiarrhythmics