N-Acetyl-procainamide kinetics in the elderly.

Area of Science:

• Pharmacokinetics
• Geriatric Medicine
• Analytical Chemistry

Background:

• N-acetyl-procainamide (NAPA) is a metabolite of procainamide.
• Understanding NAPA pharmacokinetics is crucial for therapeutic drug monitoring, especially in elderly populations.
• High-performance liquid chromatography (HPLC) is a standard analytical technique for drug concentration measurement.

Purpose of the Study:

• To characterize the plasma and saliva concentrations of N-acetyl-procainamide (NAPA) in elderly patients.
• To determine the pharmacokinetic parameters of NAPA following intravenous administration.
• To assess the utility of saliva as a matrix for monitoring NAPA levels in older individuals.

Main Methods:

• Intravenous infusion of 750 mg NAPA to 14 elderly patients (mean age 69 years).
• Plasma and saliva samples collected and analyzed using high-performance liquid chromatography (HPLC).
• Pharmacokinetic analysis using a two-compartment body model.

Main Results:

• Plasma NAPA disappearance followed a two-compartment model.
• Mean pharmacokinetic parameters: total body clearance 10.6 L/hr, Vdss 125.8 L, terminal half-life (t 1/2) 8.8 hr.
• Nonrenal clearance was 2.72 L/hr (19% of expected total body clearance).
• Saliva NAPA concentrations exhibited significant inter- and intraindividual variability.

Conclusions:

• NAPA disposition in elderly patients can be described by a two-compartment model.
• Nonrenal clearance contributes a notable portion to NAPA elimination in this population.
• Saliva is not a reliable matrix for monitoring NAPA in older patients due to high variability.