Procainamide

• Class IA antidysrhythmic agent

• Blocks cardiac sodium channels
• Decreases conduction velocity in the ventricles
• Delays myocardial repolarization
• Widening of QRS and prolonged QT interval

Antidysrhythmic medication for:

• Stable ventricular tachycardia

• Paroxysmal SVT uncontrolled by adenosine or vagal maneuvers
• Stable wide QRS tachycardia
• Atrial fibrillation with rapid ventricular rate in Wolff-Parkinson-White syndrome

• Onset: Immediately with IV push
• Peak: (oral) 1 hour
• Half-Life: 3 hours
• Metabolism:  Metabolized in liver and excreted by kidneys

• Dizziness, psychosis
• Hypotension, ventricular fibrillation, AV blocks, flushing
• Agranulocytosis with chronic use, thrombocytopenia
• (PO doses) bitter taste, nausea, vomiting, anorexia, diarrhea
• SLE Syndrome if used for prolonged periods > 1 year (inflammation of joints, fever, pericarditis, hepatomegaly, antinuclear antibodies = ANA's)
• Anticholinergic effects (tachycardia, mydriasis, constipation, urinary retention)–not as common as with quinidine

• Cardiotoxicity:  widening of QRS (> 50%) and prolonged QT interval
• Hypotension

• Myasthenia gravis or  SLE
• Hypersensitivity to procainamide or procaine
• Blood dyscrasias
• 2nd or 3rd degree AV block
• Use caution if renal, cardiac, or liver impairment is present.  Procainamide may precipitate hypotension in left ventricular failure or impaired function.
• May cause dysrhythmias in the presence of acute MI, hypokalemia, or hypomagnesemia.

• Intravenous: 20 mg/min slow IV bolus until: 1) maximum dose of 17 mg/kg (around 600 mg), 2) dysrhythmia is suppressed, 3) hypotension develops, 4) QRS widens > 50%
• IV Drip:  1 – 4 mg/min diluted in D₅W or NS

• Drug Interactions:  1) Other antidysrhythmic drugs may exacerbate prolonged QT interval; 2) Antihypertensive agents may compound hypotension effect; 3) Anticholinergic drugs may enhance anticholinergic symptoms; 4) Cimetidine may increase procainamide serum levels.
• Incompatibilities with intravenous infusion include bretylium, esmolol, ethacrynate, milrinone, and amrinone.
• Check apical pulse, BP, and cardiac monitor prior to administration of procainamide.
• Monitor blood pressure, QRS duration, and QT interval frequently for patients receiving procainamide.
• Serum procainamide levels should be between 3 – 10 mcg/ml
• Quinidine is preferred over procainamide for long term suppression of dysrhythmias due to probability of SLE syndrome and blood dyscrasias.
• Obtain baseline cardiac rhythm strip, CBC, lab tests for liver and renal functions, and blood pressure.
• When converting from IV infusion to oral doses, allow 3 hours after termination of infusion before administering first oral dose.
• During conversion of atrial fibrillation, patient may develop thromboembolism (sudden chest pain, dyspnea, or CVA).