Procainamide

Aka: Procainamide, Pronestyl

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II. Mechanism

  1. See Class Ia Antiarrhythmic
  2. Suppresses ventricular ectopy
    1. Suppresses Phase 4 diastolic depolarization
    2. Reduces automaticity of all Pacemakers
  3. Slows intraventricular conduction
    1. May terminate reentrant Arrhythmias

III. Indications

  1. Ventricular Tachycardia (refractory to Lidocaine)
  2. Ventricular Fibrillation
  3. Atrial Fibrillation with accessory pathway (preexcitation, WPW) rate control and cardioversion
    1. Time to Cardioversion: 1 hour
    2. Conversion Rate: 20%
    3. Chronic Efficacy: 50%

IV. Contraindications

  1. Structural Heart Disease (e.g. Acute Myocardial Infarction, LV Dysfunction)
    1. Risk for lethal ventricular Arrhythmias and increased mortality
  2. Hypokalemia
  3. Hypomagnesemia
  4. Systemic Lupus Erythematosus
    1. Risk of blood dyscrasias

V. Precautions

  1. Proarrhythmic
    1. Risk for ventricular Arrhythmias and mortality in structural heart disease (Acute Myocardial Infarction, LV Dysfunction)
  2. Monitoring
    1. Blood Pressure Monitoring
    2. Electrocardiogram Monitoring
    3. Complete Blood Count (esp. White Blood Cells and Platelet Count)
    4. Toxic metabolite N-acetylprocainamide (NAPA)

VI. Dosing

  1. Preparation of Procainamide Infusion
    1. Dilute 2 g in 250 ml D5W (8 mg/ml)
  2. Endpoints to Dosing
    1. Arrhythmia is suppressed
    2. Hypotension
    3. QRS Complex widening over 50% of original width
    4. PR Interval or QT Interval lengthening over 50%
    5. Maximum total dose reached: 17 mg/kg or 1000 mg administered
  3. Child
    1. Load
      1. Start 2 to 6 mg/kg (up to 100 mg) IV infused over 5 minutes
      2. Repeat dose every 5 to 10 min as needed up to cummulative maximum of 15 mg/kg
    2. Maintenance
      1. Infuse 20 to 80 mcg/kg/minute
      2. Maximum 2 grams/day
  4. Adult
    1. Load
      1. Infuse 20 mg/min (or 100 mg IV every 10 minutes) until any above endpoint reached
      2. Max Total Dose: 17 mg/kg or 1000 mg administered
    2. Maintenance: 1-4 mg/min (up to 6 mg/min)
      1. Start after effect is achieved with loading dose
  5. Liver Disease
    1. Decrease dose or decrease dosing frequency
  6. Renal Insufficiency
    1. GFR 35 to 59 ml/min
      1. Decrease initial maintenance dose by 30%
    2. GFR 15 to 34 ml/min
      1. Decrease initial maintenance dose by 40 to 60%
    3. GFR <15 ml/min
      1. Reduce dose, Exercise caution and monitor closely

VII. Adverse Effects

  1. Common
    1. Electrocardiogram changes
      1. QRS Complex widening
      2. PR Interval lengthening
      3. QTc Prolongation
  2. Serious
    1. Hypotension
    2. Atrioventricular conduction disturbance
      1. AV Block
      2. Cardiac Arrest
    3. Malignant Ventricular Arrhythmia
      1. Torsades de Pointes
      2. May parodoxically increase the ventricular response to atrial tachyarrhythmia
    4. Blood Dyscrasias (esp. in Systemic Lupus Erythematosus)

VIII. Pharmacokinetics

  1. Low Protein Binding
  2. Hepatic metabolism with renal excretion
  3. Metabolized to the active, and toxic metabolite N-acetylprocainamide (NAPA)

IX. Safety

  1. Pregnancy Category C
  2. Unknown safety in Lactation

X. References

  1. Procainamide Injection Solution (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=17e47845-daad-434c-a784-6d3875b0d704

XI. References

  1. Olson (2020) Clinical Pharmacology, Medmaster Miami, p. 78-9
  2. Hamilton (2020) Tarascon Pocket Pharmacopoeia

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