Cytochrome P450 2C9
CYP2C9 metabolizes warfarin, phenytoin, celecoxib, and some NSAIDs.[1] Variants that reduce its activity are most consequential for warfarin, where even small changes in drug clearance translate into very different doses (and a real bleeding risk if missed).[2]
Gene2Rx reports your CYP2C9 genotype across 61 named star alleles, built from 58 variants curated by PharmVar.
Star alleles (like *1, *2, *4) are standardized names for distinct versions of a pharmacogene. *1 is the reference; higher numbers identify variants discovered later that change the enzyme's activity.
You inherit one allele from each parent, so your genotype is a pair (e.g. *1/*4). The pair determines your predicted phenotype — for example, whether you metabolize a drug at a normal, decreased, or no-function rate.
PharmVar is the international registry that defines and curates these allele names. Gene2Rx tests the variants required to call every CYP2C9 allele in the PharmVar catalog.
Gene2Rx covers 16 medications with published pharmacogenetic guidance for CYP2C9, drawn from CPIC and FDA sources. Each drug links to its full pharmacogenetics page.
These branded medications include at least one active ingredient whose metabolism or action involves CYP2C9. Each links to its full pharmacogenetic breakdown.
This page lists drugs affected by CYP2C9. A Gene2Rx report tells you which metabolizer group you fall into, and what that means for every medication on this list.
Get your report Look up a medicationInformational only, not medical advice. The presence of a CYP2C9 pharmacogenetic guideline does not mean every patient needs to change their dose. Never start, stop, or change a medication without talking to your prescribing clinician.