{{Rsnum
|rsid=2235040
|Gene=ABCB1
|Chromosome=7
|position=87536434
|Orientation=plus
|GMAF=0.1267
|Assembly=GRCh38
|GenomeBuild=38.1
|dbSNPBuild=141
|geno1=(A;A)
|geno2=(A;G)
|geno3=(G;G)
|Gene_s=ABCB1
}}{{ population diversity
| geno1=(A;A)
| geno2=(A;G)
| geno3=(G;G)
| CEU | 0.9 | 27.4 | 71.7
| HCB | 0.0 | 9.5 | 90.5
| JPT | 1.8 | 15.9 | 82.3
| YRI | 7.5 | 33.3 | 59.2
| ASW | 3.5 | 29.8 | 66.7
| CHB | 0.0 | 9.5 | 90.5
| CHD | 0.0 | 6.4 | 93.6
| GIH | 2.0 | 32.7 | 65.3
| LWK | 4.6 | 32.1 | 63.3
| MEX | 0.0 | 20.7 | 79.3
| MKK | 5.8 | 28.4 | 65.8
| TSI | 2.0 | 27.5 | 70.6
| HapMapRevision=28
}}[[rs2235040]] is a SNP in the [[ABCB1]] gene (also known as the MDR1 gene), which encodes a protein that transports certain molecules across the blood-brain barrier. SNPs in [[ABCB1]] may thus influence the intracerebral concentrations of certain drugs and thus their efficacy or potential for adverse side effects. [[rs2235040]] is one of 9 SNPs found within a tight linkage block (r<sup>2</sup> >= 0.8 ) such that the minor allele at any one of them predicts (with ~80%+ accuracy) that the other SNPs will also be the minor allele. The list of the 9 SNPs is shown below.

When treated for [[depression]] with substrates of the protein encoded by [[ABCB1]], carriers of one or two minor alleles at these [[ABCB1]] SNPs have been reported to respond better than non-carriers. The [[antidepressant]] drugs that are known to be substrates include [[citalopram]], [[paroxetine]], [[amitriptyline]], and [[venlafaxine]]. The relative odds of better response for [[rs2235040]](G) carriers is 7.72 (CI: 2.8-21.3, p=0.000065) based on a study of ~400 primarily Caucasian patients.{{doi|10.1016/j.neuron.2007.11.017}}

The 9 SNPs in the linkage block identified are {{doi|10.1016/j.neuron.2007.11.017}}:
* [[rs2235067]]
* [[rs4148740]]
* [[rs2032583]]
* [[rs4148739]]
* [[rs11983225]]
* [[rs2235040]]
* [[rs12720067]]
* [[rs7787082]]
* [[rs10248420]]

{{ neighbor
| rsid = 10248420
| distance = 764
}}

{{PharmGKB
|RSID=rs2235040
|Name_s=
|Gene_s=ABCB1
|Feature=Intron
|Evidence=PubMed ID:18215618
|Annotation=This variant is associated with differences in clinical efficacy of antidepressants, most likely by influencing their access to the brain.
|Drugs=amitriptyline; citalopram; paroxetine; venlafaxine
|Drug Classes=
|Diseases=Depression
|Curation Level=Curated
|PharmGKB Accession ID=PA161615699
}}

{{PMID Auto
|PMID=18382661
|Title=Pharmacokinetic genes do not influence response or tolerance to citalopram in the STAR*D sample.
|OA=1
}}

{{PMID Auto
|PMID=22641028
|Title=ABCB1 gene variants influence tolerance to selective serotonin reuptake inhibitors in a large sample of Dutch cases with major depressive disorder.
}}

{{GET Evidence
|impact=pharmacogenetic
|qualified_impact=Insufficiently evaluated pharmacogenetic
|inheritance=unknown
|quality_scores=Array
|dbsnp_id=rs2235040
|overall_frequency_n=1496
|overall_frequency_d=10758
|overall_frequency=0.139059
|n_genomes=13
|n_genomes_annotated=0
|n_haplomes=16
|n_articles=1
|n_articles_annotated=0
|in_pharmgkb=Y
|autoscore=2
|webscore=N
|n_web_uneval=10
}}

{{on chip | 23andMe v1}}
{{on chip | 23andMe v2}}
{{on chip | 23andMe v3}}
{{on chip | 23andMe v4}}
{{on chip | Affy GenomeWide 6}}
{{on chip | FTDNA2}}
{{on chip | HumanOmni1Quad}}
{{on chip | Illumina Human 1M}}