Name: Procainamide (Pronestyl)
Class: Antidysrhythmic Agent (Class IA)
Mechanism: Binds to open and inactivated Na+ channels and prevents Na+ influx ® slowing of the rapid upstroke during phase 0. Also decreases the slope of phase 4 spontaneous depolarization. Prolongs repolarization. Inhibits arrhythmias due to normal automaticity. Intermed. speed of dissociation from Na+ channels.
Absorption: Oral. IV rarely used, as hypotension occurs w/too rapid infusion.
Dist.: Excretion, t½: Urine. 2-3 hr.
Metabolism.: Hepatic ® active Metabolismolite NAPA ( duration of action potential).
Toxicity/S.E.s: Proarrhythmic effects, negative inotropy, infranodal conduction block, DILQT. Hypotension (ganglion-blocking activity). Chronic use ® reversible SLE-like synd. Depression, hallucination, psychosis, giddiness. Less GI intolerance than quinidine. Hypersensitivity rxns—fever, agranulocytosis, Raynaud’s synd., myalgias, rashes, digital vasculitis.
Utility: Treat atrial, AV junctional, & ventricular tachyarrhythmias. Maintain sinus rhythm after direct current cardioversion of atrial flutter or fibrillation. Prevent frequent ventricular tachycardia.