ABCB1 rs1045644: What Your Genotype Means
The rs1045644 variant is a common genetic change located within the ABCB1 gene, which encodes a critical drug-transporting protein. Research has investigated its potential role in influencing how the body processes various cardiovascular medications, though evidence regarding its clinical impact remains limited.
What each genotype means
Common genetic variant
This is the most frequently observed genotype for this variant in many populations. Research into this specific ABCB1 variant has shown limited and inconsistent evidence regarding its impact on medication response or clinical outcomes. Please discuss any concerns about your medication efficacy or dosing with your clinician or pharmacist.
This is the most common genotype found across most major continental ancestries.
Common genetic variant
You carry one copy of each allele for this variant. Current scientific literature indicates that the association between this ABCB1 variant and clinical traits remains limited and requires further study. Always consult with your healthcare provider or pharmacist regarding your specific medication management.
This heterozygous genotype is observed frequently in diverse populations worldwide.
Common genetic variant
You carry two copies of the G allele for this variant. While some studies investigate ABCB1 variants in relation to drug response or health traits, the evidence for this specific variant is currently considered limited and inconclusive. Please speak with your doctor or pharmacist if you have questions about how your genetics might relate to your health or medications.
This genotype is present at a moderate frequency across major continental ancestries.
Understanding the rs1045644 Variant
The rs1045644 variant is a single nucleotide polymorphism (SNP) found within the ABCB1 gene, also historically known as the MDR1 gene. This specific variant is classified as a synonymous exon 26 variant, meaning that while it changes the DNA sequence, it does not alter the primary amino acid sequence of the resulting protein. Despite this, researchers have long hypothesized that such variants might influence the stability of the messenger RNA (mRNA) or the efficiency of protein folding. Located on chromosome 7, this SNP is one of several variations within the ABCB1 gene that scientists study to understand why individuals may respond differently to the same pharmaceutical treatments. Because it does not change the protein's structure directly, its functional consequences are often subtle and difficult to isolate from other genetic and environmental factors.
The Role of the ABCB1 Gene
The ABCB1 gene provides instructions for creating a protein called P-glycoprotein, which acts as an ATP-dependent efflux pump. This protein is essential for protecting the body by transporting various substances, including toxins and drugs, out of cells. P-glycoprotein is highly active in the blood-brain barrier, the liver, the kidneys, and the intestines, where it regulates the absorption and distribution of many medications. By pumping drugs back into the bloodstream or out of the body, P-glycoprotein can significantly influence the concentration of a drug at its target site. When the activity of this pump is altered—whether by genetic variation, drug interactions, or disease states—it can lead to differences in how effectively a medication works or how likely a patient is to experience side effects.
Research and Clinical Evidence
Scientific interest in rs1045644 stems from its potential to affect the pharmacokinetics of cardiovascular drugs, such as antiplatelet agents or statins. While some studies have suggested that this variant might be linked to variable drug responses, the overall evidence remains limited and often inconsistent across different populations. Many studies have failed to find a statistically significant association between this specific SNP and clinical outcomes, such as the efficacy of clopidogrel or other common heart medications. Because drug response is a complex trait influenced by multiple genes, age, diet, and other medications, it is difficult to attribute clinical outcomes to a single SNP. Consequently, current medical guidelines do not typically recommend routine testing for this variant to guide dosing decisions. Patients should always consult their healthcare provider or pharmacist regarding any concerns about their medication regimen.
What You Can Do With This Information
Genetic information regarding variants like rs1045644 is primarily used for research purposes to better understand human biology and drug metabolism. It is important to recognize that having a particular genotype for this variant does not serve as a diagnostic tool or a definitive predictor of how you will respond to a specific medication. If you have received genetic testing results that mention this variant, it is best to view them as one small piece of a much larger puzzle. You should never make changes to your prescribed medications based on genetic reports without first speaking to your doctor. Your clinician can integrate your genetic information with your clinical history, current health status, and other relevant factors to ensure your treatment plan is safe and appropriate for your individual needs.
How common is this variant?
The rs1045644 variant is common, with a minor allele frequency typically ranging between 0.20 and 0.35 across major continental ancestries.
Frequently asked questions
Does rs1045644 mean I am resistant to my heart medication?
No. Current research does not support using this variant to predict medication resistance. Drug response is influenced by many factors, and this SNP alone is not a reliable indicator of how a drug will work for you.
Should I get tested for ABCB1 variants?
Routine testing for this variant is not currently recommended by clinical guidelines. If you have questions about your medication, discuss them with your doctor or pharmacist rather than seeking independent genetic testing.
Is rs1045644 the same as the C3435T polymorphism?
Yes, rs1045644 is the official rsID for the commonly studied C3435T polymorphism in the ABCB1 gene. Both terms refer to the same genetic location.
Can I change my dose if I have the TT genotype?
Absolutely not. Never adjust your medication dosage based on genetic test results. Only a qualified healthcare professional can determine if a dosage adjustment is necessary based on your full clinical profile.
Sources & further reading
Educational information only, last refreshed 10/16/2026. 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 polymorphism in the ABCB1 (MDR1) transporter gene influencing substrate drug efflux and systemic drug exposure.