N-Acetylprocainamide kinetics after single and repeated oral doses

Area of Science:

• Pharmacokinetics
• Clinical Pharmacology
• Cardiology

Background:

• N-acetylprocainamide (NAPA) is a metabolite of procainamide with potential therapeutic applications.
• Understanding NAPA's pharmacokinetic profile is crucial for optimizing its use, especially in patient populations with altered physiological functions.

Purpose of the Study:

• To investigate the kinetic behavior of N-acetylprocainamide (NAPA) following single and repeated oral doses.
• To compare NAPA's renal clearance and steady-state concentrations in healthy subjects versus patients with cardiomyopathy.
• To assess the relationship between NAPA clearance and creatinine clearance in both groups.

Main Methods:

• Single and repeated oral doses of NAPA were administered to healthy volunteers and patients with cardiomyopathy.
• Renal clearance (CLR) and creatinine clearance (ClCR) were measured.
• NAPA serum concentrations were monitored to determine steady-state levels and oral clearance.
• A published regression formula was used to predict the NAPA CLR to ClCR ratio (R).

Main Results:

• Patients with cardiomyopathy exhibited significantly lower NAPA renal clearance compared to healthy subjects, independent of creatinine clearance.
• The ratio of NAPA CLR to ClCR was lower in patients, and a published formula inaccurately predicted this ratio for them.
• Mean steady-state NAPA concentrations were higher in patients, and oral clearance decreased slightly after repeated dosing.
• NAPA serum concentrations were generally proportional to the administered dose across the studied range.

Conclusions:

• Cardiomyopathy is associated with impaired renal clearance of N-acetylprocainamide.
• Dosage adjustments may be necessary for NAPA in patients with cardiomyopathy to avoid potential accumulation.
• The deacetylation of NAPA to procainamide is minimal, suggesting NAPA's pharmacokinetic profile is primarily influenced by clearance mechanisms.