CYP2D6 rs28371725: Understanding the *41 Allele
The rs28371725 variant is a specific single nucleotide polymorphism located within the CYP2D6 gene. It is a defining component of the CYP2D6*41 allele, which is associated with reduced metabolic capacity for various medications.
What each genotype means
Typical metabolic capacity
This genotype represents the most common form of the CYP2D6 promoter region. Individuals with this profile typically exhibit standard enzyme activity levels for the metabolism of various neuropsychiatric medications. Please discuss any medication dosing or treatment plans with your clinician or pharmacist.
This is the most common genotype observed in most global populations.
Reduced metabolic capacity
This genotype includes one copy of the variant associated with the CYP2D6*41 allele, which can lead to alternative splicing and reduced enzyme function. You may process certain medications more slowly than individuals without this variant, which could influence drug levels in your body. Please consult your healthcare provider or pharmacist regarding how this may affect your specific medication regimen.
Carried by roughly 8-10% of people of European and Middle Eastern ancestry; it is significantly less common in East Asian populations.
Decreased metabolic capacity
This genotype indicates the presence of two copies of the variant associated with the CYP2D6*41 allele, which is linked to reduced metabolic capacity for several neuropsychiatric drugs. Because your enzyme activity may be lower than average, your body might process certain medications differently. Always discuss your genetic results and medication dosing with your clinician or pharmacist.
This genotype is relatively uncommon, occurring in a small fraction of European and Middle Eastern populations and is rare in East Asian populations.
What is rs28371725?
The rs28371725 variant is a genetic change located in the CYP2D6 gene, which provides instructions for making an enzyme essential for processing many drugs. This specific SNP is a key marker used to identify the CYP2D6*41 allele. In genetics, an allele is a variant form of a gene. When this specific change is present, it can lead to alternative splicing of the gene's instructions, which often results in the production of an enzyme with lower functional activity compared to the standard, fully active version. Because the CYP2D6 enzyme is responsible for breaking down a significant portion of commonly prescribed medications, variations that alter its function are of great interest in the field of pharmacogenomics, which studies how genes influence an individual's response to drugs.
The Role of the CYP2D6 Gene
The CYP2D6 gene belongs to the cytochrome P450 family, a group of enzymes primarily found in the liver that act as the body's chemical processing plant. These enzymes are responsible for metabolizing, or breaking down, a wide array of substances, including many neuropsychiatric drugs, antidepressants, and pain medications. Because the gene is highly polymorphic—meaning it has many different variations across the human population—individuals can have vastly different abilities to process these medications. Some people are 'ultrarapid' metabolizers, while others are 'poor' or 'intermediate' metabolizers. The *41 allele, defined in part by rs28371725, is categorized as a decreased-function allele. This means that individuals carrying this variant may process certain drugs more slowly than those with fully functional versions of the gene, potentially leading to higher concentrations of the drug in their system.
Research and Clinical Evidence
Research into rs28371725 and the *41 allele is ongoing, with evidence currently considered limited regarding its precise clinical impact across all drug classes. Studies have shown that the *41 allele contributes to an intermediate metabolizer phenotype. In clinical settings, researchers use an 'activity score' to predict how a patient might respond to a drug based on their CYP2D6 genotype. The *41 allele is often assigned a reduced activity value in these calculations. However, because drug metabolism is complex and influenced by many factors—including other genetic variants, drug-drug interactions, and environmental factors—the presence of this SNP does not guarantee a specific clinical outcome. The evidence is strongest in the context of pharmacogenetic research, where it helps explain why some patients experience different side effects or therapeutic responses than others when taking the same medication.
Population Frequency
The frequency of the CYP2D6*41 allele varies significantly across different global populations. It is relatively common in European and Middle Eastern populations, where it has been observed at frequencies of approximately 8% to 11%. In contrast, this variant is quite rare in East Asian populations, often appearing at frequencies of less than 1%. Understanding these population-specific differences is a major focus of global pharmacogenetic studies, as it helps clinicians anticipate which genetic variations might be more prevalent in specific patient groups.
Managing Your Genetic Information
If you have received information about your CYP2D6 status, it is important to understand that this is only one piece of a much larger puzzle. Genetic testing for pharmacogenomics is a tool to help clinicians make more informed decisions, but it should never be used to self-diagnose or alter medication regimens. If you are concerned about how your body processes a specific medication, or if you have experienced unexpected side effects, you should discuss these findings with your doctor or a pharmacist. They can interpret your results in the context of your overall health, current medications, and medical history. Never stop or change the dosage of a prescribed medication without professional medical guidance, as doing so can be dangerous. Genetic data provides insights into potential risks, but clinical decisions must always be made by a qualified healthcare provider.
How common is this variant?
The CYP2D6*41 allele is common in European and Middle Eastern populations at approximately 8-11%, but is rare in East Asian populations at less than 1%.
Frequently asked questions
What does it mean to be an intermediate metabolizer?
An intermediate metabolizer has a reduced ability to process certain drugs compared to the average person. This may result in the drug staying in the body longer, which could increase the risk of side effects.
Does having the rs28371725 variant mean I cannot take certain medications?
Not necessarily. This variant is just one factor that influences how you process drugs. Your doctor will consider your entire genetic profile, medical history, and other medications before determining the best treatment plan.
Should I get tested for CYP2D6 variants?
Pharmacogenetic testing is usually recommended by a doctor if you are having trouble finding the right medication or dosage. You should discuss the necessity and potential benefits of such testing with your healthcare provider.
Is rs28371725 the same as the *41 allele?
The rs28371725 SNP is a defining marker for the CYP2D6*41 allele. While they are closely linked, the *41 allele is a specific combination of genetic changes that includes this SNP.
Sources & further reading
Educational information only, last refreshed 9/28/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Get my report — $29Related variants in CYP2D6
This variant is a key marker for the CYP2D6*10 allele, which results in reduced enzymatic activity and altered metabolism of various psychiatric and analgesic medications.
This variant defines the CYP2D6*4 non-functional allele, which causes impaired metabolism of numerous clinically prescribed medications including antidepressants, tamoxifen, and codeine.
Defines the CYP2D6*17 allele (p.Thr107Ile), which exhibits reduced enzyme activity towards substrates like codeine and certain antidepressants.
Defines the CYP2D6*29 variant (p.Val338Met) conferring decreased metabolic capacity, primarily observed in populations of African descent.
Defines the non-functional CYP2D6*41 splice defect associated with intermediate metabolizer phenotype affecting codeine, tamoxifen, and SSRI metabolism.
Defines the CYP2D6*6 deletion variant (1707delT) leading to a premature stop codon and loss of enzyme function.