CYP2B6 rs56113826: What Your Genotype Means
The rs56113826 variant is a well-studied genetic change in the CYP2B6 gene that is associated with reduced enzyme activity. This variant, often referred to as the *6 allele, can influence how an individual metabolizes certain medications, including antidepressants and HIV treatments.
What each genotype means
Normal enzyme activity
This genotype is typically associated with normal metabolism of drugs processed by the CYP2B6 enzyme, such as bupropion and efavirenz. Individuals with this profile generally exhibit standard drug clearance rates. Please discuss any medication dosing or concerns with your clinician or pharmacist.
This is the most common genotype in many populations, though frequencies vary significantly by ancestry.
Reduced enzyme activity
This genotype, often associated with the CYP2B6*6 or *9 alleles, is linked to reduced metabolism of certain medications like efavirenz and bupropion. Research indicates that carriers may experience altered drug concentrations, which can influence both efficacy and the risk of side effects. Please consult your healthcare provider or pharmacist regarding how this may affect your specific medication regimen.
This genotype is common globally, with carrier frequencies ranging from approximately 15% to 40% depending on ethnic background.
Significantly reduced enzyme activity
This genotype is associated with a marked reduction in the activity of the CYP2B6 enzyme, which can lead to higher plasma concentrations of drugs like efavirenz. Clinical studies suggest this may increase the risk of neuropsychiatric side effects for certain medications. It is important to discuss this genetic finding with your clinician or pharmacist to ensure appropriate medication selection and dosing.
This genotype is less common than the heterozygous state, with the highest prevalence observed in populations of African and Papua New Guinean descent.
Understanding the rs56113826 Variant
The rs56113826 variant is a specific change in the DNA sequence of the CYP2B6 gene. In the context of pharmacogenomics, this variant is frequently identified as part of the *6 allele, which is a combination of two specific genetic changes that result in a less functional enzyme. Because this variant is common across many global populations, it has been the subject of extensive research to understand how it alters the body's ability to break down drugs. When a person carries this variant, the CYP2B6 enzyme may work less efficiently than the standard version, potentially leading to differences in how medications are processed in the bloodstream. It is important to note that genetic variants are just one of many factors, including age, diet, and other medications, that influence how a person responds to a drug.
The Role of the CYP2B6 Gene
The CYP2B6 gene provides instructions for making an enzyme that belongs to the cytochrome P450 family. These enzymes are primarily located in the liver and are responsible for metabolizing a wide range of substances, including toxins and therapeutic drugs. By breaking down these compounds, the CYP2B6 enzyme helps the body clear medications from the system. When the gene contains variants like rs56113826, the resulting enzyme may have reduced activity or stability. This can lead to slower metabolism of drugs that rely on this specific pathway. For example, research has shown that individuals with reduced-function CYP2B6 variants may have different concentrations of drugs like bupropion or efavirenz in their blood compared to those with the most common, fully functional version of the gene.
Research and Clinical Associations
Scientific research has established a strong association between the rs56113826 variant and altered drug metabolism. Studies have consistently shown that carriers of this variant often exhibit reduced formation of active metabolites for drugs such as bupropion, an antidepressant. Similarly, in the context of HIV treatment, this variant has been linked to variations in plasma concentrations of efavirenz. The evidence for these associations is considered strong within the field of pharmacogenomics. However, the clinical impact can vary significantly between individuals. While some people may experience different drug levels, this does not always translate to a noticeable difference in clinical outcomes or side effects. Because of this complexity, researchers emphasize that genetic testing is a tool to help clinicians make informed decisions rather than a definitive predictor of how a patient will respond to a specific medication.
Population Frequency
The rs56113826 variant is relatively common, with frequencies varying significantly across different ancestral groups. Research indicates that the *6 allele, which includes this variant, is present in 15% to 40% of individuals depending on their ethnicity. It is found across most major ethnogeographic groups, though the specific prevalence rates differ, with some populations showing higher frequencies of reduced-function alleles than others.
What This Information Means for You
Knowing your genotype for rs56113826 provides insight into your genetic predisposition for drug metabolism, but it is not a medical diagnosis. Genetic information is only one piece of a larger puzzle that your healthcare provider uses to determine the best treatment plan. If you have concerns about how a medication is affecting you, or if you are curious about how your genetics might influence your response to a drug, the most important step is to have a conversation with your doctor or pharmacist. They can interpret your results in the context of your overall health, current medications, and medical history. Never make changes to your prescribed medication regimen based on genetic test results without consulting a qualified medical professional, as they are best equipped to balance the risks and benefits of your treatment.
How common is this variant?
The rs56113826 variant is common, with the associated *6 allele appearing in 15-40% of individuals depending on their ancestral background.
Frequently asked questions
Does having the rs56113826 variant mean I cannot take certain medications?
No, having this variant does not mean you cannot take a medication. It simply means your body might process that drug differently, which your doctor can account for when determining the appropriate dosage or selecting an alternative treatment.
Is a genetic test for CYP2B6 required before starting antidepressants?
Routine genetic testing is not required for everyone starting antidepressants. However, if a patient experiences unexpected side effects or a lack of response to a standard dose, a clinician may consider pharmacogenetic testing to see if genetic factors are contributing to the issue.
Can I change my CYP2B6 genotype?
No, your genotype is determined by the DNA you inherited from your parents and cannot be changed. It is a permanent part of your genetic makeup.
Where can I get tested for this variant?
Pharmacogenetic testing is typically ordered by a healthcare provider if they believe it will help guide your treatment. You should discuss the necessity and potential benefits of such testing with your doctor or a genetic counselor.
Sources & further reading
Educational information only, last refreshed 9/30/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Defines the non-functional CYP2B6*18 allele (c.983T>C; p.Ile328Thr) leading to impaired metabolism of efavirenz.
Core coding variant c.1459C>T (p.Arg487Cys) defining CYP2B6*5, associated with reduced clearance of substrates.
Key variant defining the CYP2B6*6 reduced-function allele influencing efavirenz, methadone, and bupropion clearance.
Missense alteration defining the CYP2B6*18 allele, causing profound enzymatic deficiency and impaired clearance of efavirenz and methadone.
A coding variant that defines the decreased-function CYP2B6*4 allele, influencing plasma concentrations of efavirenz, methadone, and bupropion.
Missense alteration defining the nonfunctional CYP2B6*18 allele common in African populations that slows clearance of efavirenz.