Procainamide is a class 1a antiarrhythmic that is used to treat various ventricular and atrial arrhythmias. Procainamide and its breakdown product, N-acetylprocainamide (NAPA), are both powerful antiarrhythmics that necessitate careful monitoring.
The therapeutic concentration of procainamide is 4-8 µg/mL. The half-life is 3-5 hours. The toxic concentration is 16 µg/mL or greater, although symptoms may develop at 8-10 µg/mL.
The therapeutic concentration of NAPA is also 4-8 µg/mL, and its half-life is approximately 7 hours. As with procainamide, the toxic concentration of NAPA is 16 µg/mL or greater, although symptoms may develop at 8-10 µg/mL.
The therapeutic concentration of both procainamide and N-acetylprocainamide (combined) is 30 µg/mL or less. The toxic concentration is any level in excess of the therapeutic concentration (≥30 µg/mL).