Procainamide is a medication used in the management and treatment of ventricular arrhythmias, supraventricular arrhythmias, atrial flutter, atrial fibrillation, AV nodal re-entrant tachycardia, and Wolf-Parkinson-White syndrome. It is a Class 1A antiarrhythmic agent. This activity reviews the literature, indications, action, and contraindications for procainamide as a valuable agent in the treatment of arrhythmias.
Procainamide was initially approved by the US FDA in 1950 and fell out of favor due to its side effect profile and the development of newer antiarrhythmics. Procainamide usage has increased in recent years, and it is now seen as a viable option for several arrhythmias.
Procainamide has been used for chemical cardioversion in atrial flutter and atrial fibrillation. These are common arrhythmias seen in emergency department patients, but there is no consensus for their optimal management. Stiell et al. looked at the usage of IV procainamide in 341 patients over five years. Adverse events were infrequent and included hypotension, bradycardia, atrioventricular block, and ventricular tachycardia. There were no cases of torsades de pointes, cerebrovascular accident, or death. Most patients (94.4%) received a discharge to home. IV procainamide had a 52% conversion rate of atrial fibrillation to normal sinus and a 28% conversion rate from atrial flutter to normal sinus.
One recent major study looked at the difference between amiodarone and procainamide in stable ventricular tachycardia. The PROCAMIO study has concluded that in patients with stable ventricular tachycardia, procainamide should be considered over the traditionally used amiodarone due to faster resolution of the arrhythmia, less major cardiac events and is more efficacious in a subgroup of patients with structural heart disease.
Researchers have also studied the utility of procainamide in comparison to lidocaine in terminating sustained ventricular tachycardia in patients with structural heart defects. In this retrospective study, from Circulation Journal, procainamide was found to be more effective than lidocaine in termination of the arrhythmia.
Procainamide is indicated in patients with Wolf-Parkinson-White syndrome as it is important for acute termination of antidromic AV re-entrant tachycardia in stable patients. In particular, because the use of an AV nodal blocking agent in this patient population may enhance conduction down the accessory pathway and therefore induce ventricular tachycardia or ventricular fibrillation.
Procainamide has also historically seen use in diagnostic testing for Brugada syndrome; this was known as the “procainamide challenge,” which produces the standard Brugada-like pattern on ECG, which may have been otherwise unnoticed and thus identifying patients at risk for sudden cardiac death. However, this usage has fallen out of favor, as it has low sensitivity for detecting Brugada like patterns and may also put the patient at risk of going into ventricular arrhythmia.
Procainamide is a class 1A anti-arrhythmic that binds to fast sodium channels inhibiting recovery after repolarization. It also prolongs the action potential and reduces the speed of impulse conduction. This action results in decreased myocardial excitability, slowed conduction velocity, and reduced myocardial contractility. It is possible that it acts as a negative inotrope as well and may cause peripheral vasodilation and hypotension, which may require cardioversion.
Procainamide is given IV or PO with the onset of action in 10 to 30 minutes. The loading dose is of IV procainamide is 10 to 17 mg/kg and administered at a rate of 20 to 50 mg/min. Alternatively, this may be dosed at 100 mg every 5 minutes in adult patients. The administration of this maintenance dose is from 1 to 4 mg/minute; however, the manufacturer labeling recommends 2 to 6 mg/minute.
Administration of oral procainamide dosing for supraventricular arrhythmia is at 50 mg/kg/24 hours divided into doses every 6 hours.
In the pediatric population, dosing divides into those less than 12 months in which a bolus dose of 7 to 10 mg/kg given over 15 to 30 minutes and those older than 12 months in which a bolus dose of 10 to 15 mg/kg is the regimen. An infusion rate of 20 to 50 mcg/kg/min follows the initial bolus.
Procainamide is metabolized hepatically via acetylation to form N-acetyl procainamide (NAPA) via a substrate of CYP2D6. This compound is then excreted as NAPA. The half-life of procainamide is 2.5 to 5 hrs, and the maximum dose in current recommendations is 17 mg/kg.
The adverse effects of procainamide include cardiac toxicity, bradycardia, hypotension, drug-induced lupus erythematosus like syndrome, and blood dyscrasias. QRS, QTc, and PR prolongation are the most potentially harmful cardiac side effects of procainamide and may become worse when levels of procainamide rise. Serial electrocardiograms are useful for monitoring these toxic effects during treatment with procainamide. Procainamide infusion may also increase the number of premature ventricular contractions in patients.
Another side effect of procainamide is hypotension, more commonly seen at doses of 20 mg/min. Drug-induced lupus erythematosus-like syndrome is rare, and due to the creation of positive ANA titers when taking the medication chronically. The symptoms of chronic use may include arthritis, arthralgias, and pleuritis and commonly resolve when usage stops.
Lastly, procainamide is known to cause certain blood dyscrasias. Procainamide as been known to cause bone marrow toxicity, leading to pancytopenia or agranulocytosis; this is usually due to hypersensitivity or varied immunologic mechanisms.
Use with caution in patients with heart failure, electrolyte imbalances, particularly hypokalemia and hypomagnesemia, myasthenia gravis patients, and in hepatic or renal impairment. Procainamide also crosses the placenta and may be present in the milk of breastfeeding mothers, and as such, chronic use requires caution in this population.
Procainamide monitoring during therapy of an acute arrhythmia should involve monitoring QRS duration via cardiac monitoring, and the clinician should stop therapy QRS increases by 50% of its original width. Also, blood pressure should be monitored frequently during treatment.
Toxicity from procainamide overdose is rare as it is usually given IV in a monitored setting. However, it is plausible to administer a toxic dose accidentally, or a patient with renal impairment receives an inaccurate dose. Consultation of a medical toxicologist and regional poison control center is necessary in cases of oral procainamide overdose. Treatment would theoretically be similar to an overdose of other Class 1A antiarrhythmics, including quinidine and disopyramide, in which the patient receives hypertonic sodium bicarbonate to blockade of sodium channels.
There have been several high-quality studies as well as recommendations from the American Heart Association in utilizing procainamide as a viable option to terminate a number of arrhythmias. However, procainamide should be used carefully in inpatient settings as it has several side effects that require monitoring. An interprofessional team that includes the treating physician, nurse, and pharmacist can help achieve the best possible outcomes. Care should be coordinated between the medical personnel to ensure that during therapy with procainamide, the interprofessional team takes appropriate measures. Cardiovascular monitoring, serial electrocardiograms, and frequent reassessments of the patient’s clinical status will ensure safety during usage. Instruction should be given for possible cardioversion if hypotension, bradycardia, or clinical deterioration occurs. [Level 1]
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