College of Pharmacy
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HelixTalk Episode #125 - Let’s Get Personal: Talking Warfarin Pharmacogenomics
Date posted: January 26, 2021, 6:00 am
In this episode, we will briefly review the clotting cascade and warfarin's mechanism of action, and then discuss warfarin pharmacogenetics implications and what clinical recommendations and tools are available in order to calculate warfarin dose.
- Many patient specific factors such as drug interactions, food interactions, genetic polymorphisms, and lifestyle habits are considered in successfully dosing and managing warfarin.
- Genetic polymorphisms found in either metabolizing enzyme CYP2C9, target protein VKORC1, or vitamin K oxidase CYP4F2 can alter warfarin phenotype in certain patients.
- When genetic test results for polymorphisms are available, they should be utilized for algorithm-based dosing in most patients. Such algorithms have outcomes for better TTR (time in therapeutic range), less out-of-range INRs, and shorter time to therapeutic dose.
- Certain polymorphisms are specific to different ancestry and not all commercially available tests check for these pertinent polymorphisms. CPIC guidelines provide further insight into how to use test results to derive a warfarin dose.
- Johnson JA, Caudle KE, Gong L. at el. Clinical Pharmacogenetics Implementation Consortium (CPIC) Guideline for Pharmacogenetics-Guided Warfarin Dosing: 2017 Update. Clinical Pharmacology and Therapeutics. 2017;(102)3:397-404. doi:10.1002/cpt.668 https://cpicpgx.org/content/guideline/publication/warfarin/2017/28198005.pdf
- IWPC calculator: https://cpicpgx.org/content/guideline/publication/warfarin/2011/IWPC_dose_calculator.xls
- WarfarinDosing.org: http://warfarindosing.org/Source/Home.aspx