Altered pharmacokinetics of R- and S-acenocoumarol in a subject heterozygous for CYP2C9*3

Clin Pharmacol Ther. 2001 Sep;70(3):292-8. doi: 10.1067/mcp.2001.117936.


Objective: Our objective was to study the pharmacokinetics of R - and S -acenocoumarol in a subject who was highly sensitive to the anticoagulant effect of acenocoumarol. The subject was found to be heterozygous for CYP2C9*3.

Methods: The plasma pharmacokinetics of the acenocoumarol enantiomers was established after an oral dose of 8 mg of racemic acenocoumarol. Urine was collected to establish the formation clearance of the 6- and 7-hydroxy metabolites of R - and S -acenocoumarol.

Results: The pharmacokinetics of S -acenocoumarol in this subject differed greatly (oral clearance, 6%-10%; half-life of elimination, 400%-500%) from the values of a [wt/wt] control and from population values. R -acenocoumarol clearance was at the lower level of population values. The apparent formation clearances of the metabolites were low-approximately 10% of control activity for the hydroxylations (6- and 7-) of S -acenocoumarol and for the 7-hydroxylation of R -acenocoumarol. The rate of the 6-hydroxylation of R -acenocoumarol was about 50% of control values.

Conclusion: The presence of even one copy of CYP2C9*3 reduces profoundly the metabolic clearance of S -acenocoumarol. As a result the first-pass effect of elimination is abolished and the maintenance time is increased. S -Acenocoumarol, which is normally clinically inactive, will now exert main anticoagulant activity.

Publication types

  • Comparative Study

MeSH terms

  • Acenocoumarol / pharmacokinetics*
  • Adolescent
  • Alleles
  • Anticoagulants / pharmacokinetics*
  • Aryl Hydrocarbon Hydroxylases*
  • Chromatography, High Pressure Liquid
  • Cytochrome P-450 CYP2C9
  • Cytochrome P-450 Enzyme System / genetics
  • Cytochrome P-450 Enzyme System / metabolism*
  • Drug Hypersensitivity / physiopathology
  • Exons / genetics
  • Genotype
  • Heterozygote
  • Humans
  • Male
  • Stereoisomerism
  • Steroid 16-alpha-Hydroxylase*
  • Steroid Hydroxylases / genetics
  • Steroid Hydroxylases / metabolism*


  • Anticoagulants
  • Cytochrome P-450 Enzyme System
  • Steroid Hydroxylases
  • CYP2C9 protein, human
  • Cytochrome P-450 CYP2C9
  • Aryl Hydrocarbon Hydroxylases
  • Steroid 16-alpha-Hydroxylase
  • Acenocoumarol