The pharmacokinetics of procainamide in normal subjects using a specific gas chromatographic assay

Previous procainamide pharmacokinetic studies have involved the use of colorimetric and fluorimetric methods for the determination of drug concentrations in plasma and urine. However, recent evidence shows that N-acetyl procainamide, the major metabolite in humans, is hydrolyzed during these assay procedures. As a result, a specific gas chromatographic method has been developed for the determination of procainamide in biological fluids. Using this assay procedure, the pharmacokinetics of procainamide were studied in 7 normal subjects following intravenous administration of the drug. The values of half-life (2.08 +/- 0.52 hr), volume of distribution (4.3 +/- 0.6 1/Kg) and total body clearance (1344 +/- 238 ml/min) found in this study differed from those previously reported. These discrepancies could be understood in terms of differences in assay specificity.