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Ethanol-induced increase in procainamide acetylation in man

H Olsen, J Mørland

British Journal of Clinical Pharmacology

|February 1, 1982

Summary

Ethanol significantly alters procainamide pharmacokinetics, reducing its half-life and increasing clearance. This study also highlights differences in procainamide metabolism between slow and rapid acetylators.

Area of Science:

Pharmacology
Drug Metabolism
Clinical Pharmacokinetics

Background:

Procainamide is an antiarrhythmic drug.
Ethanol is known to affect drug metabolism.
Individual variability in drug response exists, particularly related to acetylation status.

Purpose of the Study:

To investigate the impact of ethanol consumption on the pharmacokinetic profile of procainamide in humans.
To determine if ethanol influences procainamide's elimination half-life, clearance, and volume of distribution.
To assess the effect of ethanol on the formation and excretion of N-acetylprocainamide (NAPA) and explore differences based on acetylation phenotype.

Main Methods:

Two experimental designs were employed to administer ethanol relative to procainamide intake.

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Pharmacokinetic parameters including half-life (T1/2), total clearance, and volume of distribution were analyzed.

Levels of procainamide and N-acetylprocainamide in blood and urine were quantified.

Participants were categorized based on their acetylator phenotype (slow vs. rapid).

Main Results:

Ethanol significantly reduced procainamide's half-life and increased its total clearance.
The apparent volume of distribution and renal clearance of procainamide and NAPA remained unaffected by ethanol.
Ethanol increased the proportion of NAPA in blood and urine, and the NAPA/procainamide AUC ratio.
Significant differences in procainamide's T1/2 and total clearance were observed between slow and rapid acetylators.

Conclusions:

Ethanol administration alters procainamide pharmacokinetics, primarily by accelerating its elimination.
Ethanol enhances the metabolic conversion of procainamide to N-acetylprocainamide.
Individual acetylator status plays a role in procainamide pharmacokinetics, independent of ethanol's direct effects.