Procainamide 

1. INTRODUCTION

Procainamide is a Class IA antiarrhythmic (Vaughan-Williams classification) used for:

• Atrial arrhythmias
• Ventricular arrhythmias
• Particularly useful in wide-complex tachycardia of uncertain origin

 Acts by blocking fast sodium channels + prolonging repolarization

 2. MECHANISM OF ACTION

Primary action:

• Blocks fast Na⁺ channels → slows phase 0 depolarization
• ↓ Conduction velocity in atria, ventricles, His-Purkinje system

Secondary actions:

• Blocks K⁺ channels → prolongs repolarization
• ↑ Action potential duration (APD)
• ↑ Effective refractory period (ERP)

 Electrophysiological Effects

 Key risk: QT prolongation → torsades de pointes

 3. PHARMACOKINETICS 

Clinical Implication:

• Renal failure → accumulation of NAPA → torsades risk
• Slow acetylators → more procainamide toxicity

 4. INDICATIONS 

 1. Stable Wide-Complex Tachycardia

• Monomorphic VT
• Unknown origin (VT vs SVT with aberrancy)

 Recommended in American Heart Association ACLS guidelines

 2. Atrial Arrhythmias

• Atrial fibrillation (especially with accessory pathway)
• Atrial flutter

 3. WPW Syndrome 

• AF with Wolff-Parkinson-White syndrome
• Preferred drug (along with ibutilide)

 Avoid AV nodal blockers (adenosine, beta-blockers)

 4. Ventricular Arrhythmias

• Sustained VT (hemodynamically stable)
• Alternative to amiodarone

 5. CONTRAINDICATIONS

Absolute:

• Prolonged QT interval
• Torsades de pointes history
• Complete heart block (without pacing)
• Systemic lupus erythematosus (SLE)

Relative:

• Heart failure
• Renal failure
• Electrolyte imbalance (↓K⁺, ↓Mg²⁺)

 6. DOSING IN ICU

 IV Loading Dose:

• 15–18 mg/kg IV infusion
• Rate: 20–50 mg/min

 Stop if:

• QRS ↑ by 50%
• Hypotension develops
• Arrhythmia suppressed
• Max dose reached

 Maintenance Infusion:

• 1–4 mg/min IV infusion

Dose Adjustments:

7. ADVERSE EFFECTS

 Cardiac:

• QT prolongation → torsades de pointes
• Hypotension (dose-dependent)
• AV block

 Non-cardiac:

1. Drug-induced lupus 

• Arthralgia
• Fever
• Serositis
• Anti-histone antibodies

2. CNS:

• Confusion
• Psychosis (rare)

3. Hematological:

• Agranulocytosis (rare but severe)

 8. TOXICITY & MANAGEMENT

Features:

• QRS widening
• QT prolongation
• Ventricular arrhythmias

Management:

9. SPECIAL ICU SCENARIOS

1. Wide Complex Tachycardia (Stable)

• Procainamide preferred over amiodarone (less hypotension in some studies)

 2. WPW + AF

• Drug of choice
• Avoid AV nodal blockers → risk of VF

 3. Structural Heart Disease

• Use cautiously
• Amiodarone often preferred

10. GUIDELINE PEARLS 

• From American Heart Association ACLS:
• Stable monomorphic VT → procainamide infusion is recommended
• Avoid if:
• Prolonged QT
• CHF with low EF
• WPW with AF → procainamide first-line