Warfarin is metabolized by multiple proteins in the liver, including CYP2C9, VKORC1, CYP4F2, and CYP2C Cluster. 

Across populations, CYP2C9, VKORC1, CYP4F2, and CYP2C Cluster protein alleles can have different genetic variants that impact their ability to metabolize warfarin. For details about this process, visit the Clinical Pharmacogenetics Implementation Consortium's (CPIC) warfarin guidelines here. 

 

 

The Clinical Pharmacogenetics Implementation Consortium (CPIC) is a group who evaluates the evidence for the use of pharmacogenetics and then develops clinical practice guidelines.  For warfarin, extensive guideline information can be found at: https://cpicpgx.org/guidelines/guideline-for-warfarin-and-cyp2c9-and-vkorc1/ a reference maintained by CPIC. 

Here is a video that reviews the CPIC guideline for warfarin: https://youtu.be/H1YSwhPUbbg 

 

At UCHealth the use of pharmacogenetics when prescribing warfarin will occur in patients who meet the following conditions:
1) Provided a blood or saliva sample to the CCPM biobank, consented for the return of their results, and this sample has undergone genotyping OR the patient is being seen in a clinic which is currently using pharmacogenetic testing as part of standard care (e.g., the UCHealth GI Oncology Clinic).  
2) Are prescribed warfarin.

For patients enrolled in the biobank, this process takes a minimum of 4-6 weeks but may take several years. Therefore, results will not be available at initial presentation if a patient has not previously enrolled in the biobank.

If you are a provider AND your patient has CYP2C9, VKORC1, CYP4F2, or CYP2C Cluster altered metabolizer phenotype(s), a best practice alert will warn you if you attempt to prescribe warfarin (for new starts only).  The BPA will provide dosing recommendations.  

There is patient education text available for UCHealth providers to use in discharge paperwork or the after visit summary (AVS).

 

Visit our Provider FAQs page here. For immediate questions, secure chat Groups: Pharmacogenomics Service in UCHealth's EHR.