Case report: Dose adjustment of warfarin using genetic information and plasma concentration monitoring

Tohru Aomori, Y. Fujita, K. Obayashi, H. Sato, K. Kiyotani, K. Nakamura, Tomonori Nakamura, K. Yamamoto

Research output: Contribution to journalArticle

Abstract

What is known and objective Carbamazepine is known to interact with warfarin. We report on a case of this interaction and on its management using the patient's genetic information. Case summary The case concerns a 74-year-old Japanese woman with a mood disorder and a central retinal vein occlusion. She was on therapy that included carbamazepine and had started to take warfarin. However, the patient's prothrombin time expressed as the international normalized ratio (PT-INR) was 1·40 despite taking a dose three times higher than the average. The patient's S-warfarin concentration was 0·15 μg/mL and R-warfarin was 0·52 μg/mL. Her cytochrome P450 2C9 (CYP2C9) and vitamin K epoxide reductase complex, subunit 1 (VKORC1), genotypes were1/1 and -1639GA, respectively. The VKORC1 genotype indicated that she would require an even higher dose. We proposed a further increase in dose and the patient's PT-INR rose to 1·99. What is new and conclusion The patient required a high warfarin dose because of the VKORC1 genotype, and induction of CYP2C9 by carbamazepine. We improved the patient's pharmacotherapy based on her genetic information.

Original languageEnglish
Pages (from-to)319-321
Number of pages3
JournalJournal of Clinical Pharmacy and Therapeutics
Volume39
Issue number3
DOIs
Publication statusPublished - 2014

Fingerprint

Social Adjustment
Warfarin
Vitamin K Epoxide Reductases
International Normalized Ratio
Carbamazepine
Genotype
Cytochrome P-450 Enzyme System
Retinal Vein
Retinal Vein Occlusion
Prothrombin Time
Mood Disorders
Drug Therapy

Keywords

  • carbamazepine
  • cytochrome P450 2C9
  • Japanese patient
  • pharmacogenetics
  • pharmacy practice
  • therapeutic drug monitoring
  • vitamin K epoxide reductase complex, subunit 1
  • warfarin

ASJC Scopus subject areas

  • Pharmacology (medical)
  • Pharmacology
  • Medicine(all)

Cite this

Case report : Dose adjustment of warfarin using genetic information and plasma concentration monitoring. / Aomori, Tohru; Fujita, Y.; Obayashi, K.; Sato, H.; Kiyotani, K.; Nakamura, K.; Nakamura, Tomonori; Yamamoto, K.

In: Journal of Clinical Pharmacy and Therapeutics, Vol. 39, No. 3, 2014, p. 319-321.

Research output: Contribution to journalArticle

Aomori, Tohru ; Fujita, Y. ; Obayashi, K. ; Sato, H. ; Kiyotani, K. ; Nakamura, K. ; Nakamura, Tomonori ; Yamamoto, K. / Case report : Dose adjustment of warfarin using genetic information and plasma concentration monitoring. In: Journal of Clinical Pharmacy and Therapeutics. 2014 ; Vol. 39, No. 3. pp. 319-321.
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