rs3745274

A SNP in the CYP2B6 gene on chromosome 19. Its most notable genotype is T;T: If efavirenz is ever prescribed for you, lower doses may be advisable

Gene
CYP2B6
Location
Chr 1941,006,936 (GRCh38)
Highest magnitude
2.0Worth knowing
Tested on
23andMe, AncestryDNA
Minor allele frequency
27%

Genotypes

As shown in 23andMe and AncestryDNA files.

  1. G;GGoodcommon in clinvarTypical · 0.051% of people
  2. T;TMost notableBadIf efavirenz is ever prescribed for you, lower doses may be advisableWorth knowing · 2.09% of people

On SNPedia: (G;G), (T;T). Magnitude rates how notable a genotype is from 0 to 10, not how risky it is.

Frequency

Share of each genotype in 11 HapMap populations.

  • AverageG;G 51% T;T 9%
  • European ancestry (Utah)G;G 53% T;T 7%
  • Han Chinese (Beijing)G;G 66% T;T 4%
  • Japanese (Tokyo)G;G 66% T;T 6%
  • Yoruba (Nigeria)G;G 34% T;T 18%
  • African ancestry (Southwest US)G;G 47% T;T 7%
  • Chinese (Denver)G;G 69% T;T 3%
  • Gujarati IndianG;G 36% T;T 20%
  • Luhya (Kenya)G;G 47% T;T 13%
  • Mexican ancestry (Los Angeles)G;G 47% T;T 3%
  • Maasai (Kenya)G;G 40% T;T 13%
  • TuscanG;G 52% T;T 9%

Conditions, medicines and genes

Other CYP2B6 SNPs

All CYP2B6 SNPs

Notes

From SNPedia

Show notes, about 320 words

aka c.516G>T, p.Gln172His, Q172H associated with response to efavirenz Pharmacokinetics of efavirenz when co-administered with rifampin in TB/HIV co-infected patients: pharmacogenetic effect of CYP2B6 variation. The pharmacokinetics and pharmacogenomics of efavirenz and lopinavir/ritonavir in HIV-infected persons requiring hemodialysis. Polymorphisms of drug-metabolizing enzymes (GST, CYP2B6 and CYP3A) affect the pharmacokinetics of thiotepa and tepa. The impact of cytokines on the expression of drug transporters, cytochrome P450 enzymes and chemokine receptors in human PBMC. Associations between CYP2B6 polymorphisms and pharmacokinetics after a single dose of nevirapine or efavirenz in African americans. CYP2B6 (c.516G-->T) and CYP2A6 (*9B and/or *17) polymorphisms are independent predictors of efavirenz plasma concentrations in HIV-infected patients. CYP2B6 variants and plasma efavirenz concentrations during antiretroviral therapy in Port-au-Prince, Haiti. Cyclophosphamide-metabolizing enzyme polymorphisms and survival outcomes after adjuvant chemotherapy for node-positive breast cancer: a retrospective cohort study. Presence of the CYP2B6 516G> T polymorphism, increased plasma Efavirenz concentrations and early neuropsychiatric side effects in South African HIV-infected patients. Pharmacogenetics of antidepressant response. CYP2B6 polymorphisms influence the plasma concentration and clearance of the methadone S-enantiomer. Distribution of polymorphisms in cytochrome P450 2B6, histocompatibility complex P5, chemokine coreceptor 5, and interleukin 28B genes in inhabitants from the central area of Argentina. Integration of absorption, distribution, metabolism, and elimination genotyping data into a population pharmacokinetic analysis of nevirapine.

T;T

see rs3745274; poor metabolizer of efavirenz may cause CNS toxicity if given normal doses as part of HIV treatment regimen

Source and license

Adapted from rs3745274 on SNPedia, using a snapshot taken October 16, 2026. SNPedia content is shared under CC BY-NC-SA 3.0 US, and this page is shared under the same license.

SNPedia is a community-edited wiki. Its entries can be incomplete, out of date or wrong, and nothing here is a diagnosis or medical advice. Magnitude is a community rating of how interesting a genotype is, not a risk score.