Pharmacokinetic studies of procainamide (PA) and N-acetylprocainamide (NAPA) in healthy subjects.

Pharmacokinetic studies after a single oral dose of 750 mg of PA in 10 normal subjects were performed. In 6 of them, pharmacokinetics of NAPA were also determined after a single oral dose of 900 mg of NAPA. Substantial differences in pharmacokinetic parameters of PA depending on acetylation phenotype were found. In fast acetylators (sulphadimidine phenotyping), half-life was shorter (2.4 +/- 0.7 hr) and 24 hr urine NAPA excretion was larger (22.5 +/- 5.8% of dose) than in slow acetylators (3.6 +/- 1.0 hr and 8.8 +/- 5.4% respectively). NAPA was characterized by different pharmacokinetic parameters (t 1/2 7.0 +/- 1.0 hr, 24 hr urine elimination - 58.5% of dose). Clinical implications of these findings are discussed.