Pharmacology

Procainamide

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Procainamide is a type IA antiarrhythmic which prolongs repolarization via sodium channel blockade. This is achieved by slowing conduction through the ventricular His-Purkinje system thereby widening the QRS complex (and ultimately the QT interval).

As a cardiac anesthesiologist, I most often use procainamide when coming off cardiopulmonary bypass if patients are in a stable atrial fibrillation/flutter (often times I can see the right atrium fibrillating in the operative field) since procainamide slows the atrial rate and has a direct vagolytic effect on the AV node. The net effect is that more atrial impulses are actually conducted through the AV node resulting in normal A-V firing.

As far as “board questions”, procainamide is associated with bone marrow toxicity and drug-induced lupus (as are medications like isoniazid and hydralazine). Furthermore, in patients with atrioventricular accessory pathways as seen in Wolff-Parkinson-White (WPW) syndrome, atrial arrhythmias should be treated with procainamide or cardioversion rather than traditional rate control meds like beta-blockers or calcium channel blockers as these may promote conduction through the accessory pathway.

Drop me a comment with questions! 🙂

4 Comments

  1. Shahad Smaisem Reply

    You are presenting the topic in such a logic way, and in a systematic style that organize our ideas.
    Thank you sooo much
    Your topics are very helpful

  2. Sam Sahota Reply

    Great post! I did not know about the drug induced lupus part. Just mind blown right now

    • Thanks Sam! Haha, yeah it’s one of those tidbits that pops up on board exams all the time!

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