{{Rsnum
|rsid=28371685
|Gene=CYP2C9
|Chromosome=10
|position=96740981
|Orientation=plus
|ReferenceAllele=C
|MissenseAllele=T
|GMAF=0.006428
|Assembly=GRCh37
|GenomeBuild=37.1
|dbSNPBuild=131
|Summary=Warfarin (Coumadin®)
|geno1=(C;C)
|geno2=(C;T)
|geno3=(T;T)
}}
{{ population diversity
| geno1=(C;C)
| geno2=(C;T)
| geno3=(T;T)
| CEU | 0.0 | 0.0 | 0.0
| HCB | 0.0 | 0.0 | 0.0
| JPT | 99.1 | 0.9 | 0.0
| YRI | 0.0 | 0.0 | 0.0
| ASW | 96.4 | 3.6 | 0.0
| CHB | 0.0 | 0.0 | 0.0
| CHD | 0.0 | 0.0 | 0.0
| GIH | 99.0 | 1.0 | 0.0
| LWK | 96.2 | 3.8 | 0.0
| MEX | 0.0 | 0.0 | 0.0
| MKK | 54.3 | 45.7 | 0.0
| TSI | 0.0 | 0.0 | 0.0
| HapMapRevision=28
}}{{CPMC SNP
|link=https://cpmc.coriell.org/Sections/Results/Warfarin.aspx?PgId=222
}}[[rs28371685]], also known as 1003C>T, 42542C>T or R335W is a SNP in the [[CYP2C9]] gene.

The [[rs28371685]](T) allele defines the CYP2C9*11 variant, which has decreased activity.

According to [https://www.23andme.com/you/community/thread/1144/ a 23andMe discussion] This is one of the SNPs which were re-analyzed April 2009. Customers with older data may wish to redownload. SNPs effected [[rs4420638]], [[rs34276300]], [[rs3091244]], [[rs34601266]], [[rs2033003]], [[rs7900194]], [[rs9332239]], [[rs28371685]], [[rs1229984]], and [[rs28399504]].

{{PMID Auto
|PMID=20214591
|Title=Pharmacogenomics in aspirin intolerance
}}

{{PharmGKB
|RSID=rs28371685
|Name_s=CYP2C9*11;CYP2C9:R335W
|Gene_s=CYP2C9
|Feature=Exon/NonSyn
|Evidence=PubMed ID:20072124
|Annotation=Phenotype: In African Americans patients, weekly warfarin dose requirements were lower in those with the CYP2C9*8 allele (34 (30-47) mg; P = 0.023) and the CYP2C9 *2, *3, *5, *6, or *11 allele (33(28-40 mg); P < 0.001) as compared with those with the CYP2C9*1/*1 genotype (43 (35-56) mg). Adding the *5,*6,*8 and *11 alleles to a model containing the *2 and *3 alleles plus the VKORC1 -1639 G>A allele (along with clinical variables) explained 36% vs. 30% of the variability in dose requirements. Study size: 226 . Study population/ethnicity: African-American . Type of association: PD;GN;CO
|Drugs=warfarin
|Drug Classes=
|Diseases=Atrial Fibrillation; Pulmonary Embolism; Stroke; Venous Thrombosis
|Curation Level=Curated
|PharmGKB Accession ID=PA165260364
}}

{{PMID Auto
|PMID=18466099
|Title=Influence of CYP2C9 and VKORC1 on warfarin dose, anticoagulation attainment and maintenance among European-Americans and African-Americans.
|OA=1
}}

{{PMID Auto
|PMID=18752379
|Title=Warfarin pharmacogenetics.
|OA=1
}}

{{PMID Auto
|PMID=23133420
|Title=Pharmacogenomic Diversity among Brazilians: Influence of Ancestry, Self-Reported Color, and Geographical Origin.
|OA=1
}}

{{on chip | 23andMe v1}}
{{on chip | 23andMe v2}}
{{on chip | 23andMe v3}}
{{on chip | 23andMe v4}}
{{on chip | FTDNA2}}
{{on chip | HumanOmni1Quad}}
{{on chip | Illumina Human 1M}}