Procainamide (PCA)

Procainamide is a pharmaceutical antiarrhythmic agent used for the medical treatment of cardiac arrhythmias, classified by the Vaughan Williams classification system as class Ia. It is a sodium channel blocker which blocks open sodium channels and prolongs the cardiac action potential. This results in slowed conduction, and ultimately the decreased rate of rise of the action potential, which may result in widening of QRS on electrocardiogram. Procainamide is administered intravenously or orally. When administered intravenously, a loading dose should first be given, though care should be taken not to cause hypotension. Procainamide's major active metabolite is N-acetylprocainamide (NAPA), which is approximately equipotent with the parent drug as an antiarrhythmic agent. NAPA has an elimination half-life about twice that of procainamide, and it can reach somewhat higher plasma levels during chronic procainamide administration.