Warfarin sensitivity: be aware of genetic influence

Age Ageing. 2003 Mar;32(2):226-7. doi: 10.1093/ageing/32.2.226.


Background: avoidance of over anticoagulation in response to warfarin therapy would reduce risk of associated bleeding.

Subjects: two elderly patients with venous thromboembolism exhibited extreme anticoagulant response to warfarin. Both were noted to have variant CYP2C9 alleles, which reduce the metabolic capacity of cytochrome P450 2C9.

Discussion: adverse outcomes with warfarin therapy could be explained and possibly avoided by identifying patients with variant alleles for CYP2C9 before initiation of therapy.

Publication types

  • Case Reports

MeSH terms

  • Aged
  • Aged, 80 and over
  • Alleles
  • Anticoagulants / adverse effects*
  • Aryl Hydrocarbon Hydroxylases / genetics
  • Cytochrome P-450 CYP2C9
  • Female
  • Genetic Predisposition to Disease
  • Humans
  • Thrombophlebitis / drug therapy
  • Warfarin / adverse effects*


  • Anticoagulants
  • Warfarin
  • CYP2C9 protein, human
  • Cytochrome P-450 CYP2C9
  • Aryl Hydrocarbon Hydroxylases