Electrophysiological effects are similar to quinidine.

By contrast to quinidine, procainamide does not exhibit either vagolytic or alpha-adrenergic blocking activity.

Useful in acute management of supraventricular and ventricular arrhythmias.

Long term use is associated with side effects, including a drug-induced lupus syndrome which occurs at a frequency of 25% to 50%.

• In slow acetylators the procainamide-induced lupus syndrome occurs more frequently and earlier in therapy than in rapid acetylators.