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