ABCB1 rs1045485: Understanding Your Genetic Variant
The rs1045485 variant is a common genetic change located within the ABCB1 gene, which encodes a protein responsible for transporting various substances out of cells. This variant is frequently studied in pharmacogenomics due to its potential association with how different individuals respond to and metabolize specific medications.
What each genotype means
Higher transporter expression
This genotype is associated with higher levels of ABCB1 mRNA and protein compared to the T allele. Because ABCB1 acts as a drug efflux transporter, this may influence how your body processes certain medications. Please discuss your medication regimen and potential dosing adjustments with your clinician or pharmacist.
This is a common genotype found in many global populations, though frequencies vary significantly by ancestry.
Intermediate transporter expression
This genotype represents a mix of the C and T alleles, which are associated with different levels of ABCB1 transporter expression. Research suggests that the T allele may lead to lower mRNA levels than the C allele, potentially affecting drug transport. Please discuss your medication regimen and potential dosing adjustments with your clinician or pharmacist.
This heterozygous genotype is frequently observed across diverse populations worldwide.
Lower transporter expression
This genotype is associated with lower levels of ABCB1 mRNA and protein compared to the C allele. As this gene helps transport various substances out of cells, this variation may influence the efficacy or concentration of certain medications in your system. Please discuss your medication regimen and potential dosing adjustments with your clinician or pharmacist.
This genotype is common in many populations, though its prevalence varies by geographic and ethnic background.
What is rs1045485 and Where is it Located?
The rs1045485 variant, often referred to in scientific literature as the 3435C>T polymorphism, is a single nucleotide polymorphism (SNP) located within the ABCB1 gene. This gene is situated on chromosome 7 in humans. A SNP represents a variation at a single position in the DNA sequence, where one nucleotide is replaced by another. In the case of rs1045485, the substitution involves a cytosine (C) being replaced by a thymine (T). Because this variant is located within the coding region of the gene, researchers have long investigated whether this change alters the function or expression of the resulting protein. It is one of the most widely studied variants in the ABCB1 gene, serving as a focal point for understanding how subtle genetic differences can contribute to the variability observed in human drug responses across different populations.
The Role of the ABCB1 Gene
The ABCB1 gene provides instructions for making a protein known as P-glycoprotein, or multidrug resistance protein 1 (MDR1). This protein acts as an efflux pump, meaning it actively transports a wide variety of molecules, including many pharmaceutical drugs, out of cells. By pumping these substances out, P-glycoprotein plays a critical role in protecting tissues from toxins and regulating the absorption, distribution, and elimination of medications. Because it is expressed in many parts of the body, including the blood-brain barrier, the intestines, and the liver, the activity level of this protein can significantly impact the concentration of drugs in the bloodstream and their ability to reach target organs. Variations in the ABCB1 gene, such as rs1045485, are hypothesized to influence the stability of the gene's mRNA or the overall efficiency of the P-glycoprotein pump, potentially affecting how effectively a drug works or the likelihood of experiencing side effects.
Research Associations and Evidence Strength
Scientific research into rs1045485 has produced a complex body of evidence regarding its impact on drug response. Many studies have explored whether the T allele is associated with lower levels of P-glycoprotein expression compared to the C allele, which could theoretically lead to higher drug concentrations in the body. While some studies suggest links between this variant and altered responses to various medications—including certain antidepressants and cardiovascular drugs—the evidence is often described as moderate or inconsistent. Pharmacogenomic research frequently faces challenges, such as the influence of other genetic variants in linkage disequilibrium or environmental factors like diet and concurrent medication use. Consequently, while rs1045485 is a well-documented marker, it is rarely used in isolation to predict clinical outcomes. Current consensus emphasizes that while the variant is biologically relevant, its clinical utility remains an area of active investigation rather than a definitive diagnostic tool.
What You Can and Cannot Do With This Information
Understanding your genotype for rs1045485 provides insight into your genetic makeup, but it is important to interpret this information within the proper context. Genetic variants are only one piece of a much larger puzzle that determines how your body interacts with medications. Factors such as age, liver and kidney function, diet, and other medications you may be taking often play a more significant role in drug efficacy and safety than a single SNP. You cannot use this information to diagnose a condition or to make independent decisions about your prescription dosages. If you have concerns about how a medication is affecting you, or if you are interested in how your genetics might influence your treatment plan, the most appropriate step is to discuss these findings with your healthcare provider or a clinical pharmacist. They can evaluate your genetic data alongside your full medical history to provide personalized guidance.
How common is this variant?
The rs1045485 variant is common across global populations, though the frequency of the C and T alleles varies significantly depending on ancestral background.
Frequently asked questions
Is rs1045485 a diagnostic test for drug response?
No, rs1045485 is not a diagnostic test. While it is a marker of interest in pharmacogenomics, it does not provide a definitive prediction of how you will respond to a specific medication.
Should I change my medication based on my ABCB1 genotype?
You should never change your medication or dosage based on genetic information without consulting your doctor. Genetic results must be interpreted by a professional who understands your complete clinical picture.
Why do different studies show different results for this variant?
Pharmacogenomic studies often vary due to differences in study design, the specific drugs being tested, and the diverse genetic backgrounds of the participants. These factors can lead to conflicting or inconsistent findings.
Where can I find more information about my specific genetic results?
If you have received genetic testing results, you should contact the testing provider for documentation or consult with a genetic counselor. They can help explain the limitations and implications of your specific report.
Sources & further reading
Educational information only, last refreshed 10/4/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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This variant is studied for its influence on the pharmacokinetics of immunosuppressive drugs like cyclosporine and tacrolimus in transplant patients.
Synonymous variant (c.3435C>T) in ABCB1 linked to altered P-glycoprotein expression and multi-drug transporter pharmacokinetics.
Nonsynonymous variant in ABCB1 altering P-glycoprotein transporter kinetics.
A variant associated with potential differences in drug absorption and clinical outcomes in patients undergoing specific pharmacological therapies.
This SNP is linked to variations in the pharmacokinetics of drugs that are substrates for the ABCB1 transporter protein.
Synonymous exon 26 variant in ABCB1 linked to altered mRNA stability and variable response to multiple cardiovascular medications.