CYP2D6 rs601715: Understanding the *41 Reduced-Function Allele
The rs601715 variant is a specific genetic marker used to identify the CYP2D6*41 allele, which is associated with reduced enzyme activity. This variation can influence how an individual's body metabolizes certain medications, potentially impacting drug efficacy and safety.
What each genotype means
Normal enzyme activity
This genotype represents the most common form of the CYP2D6 gene at this position, typically associated with normal metabolic function. Individuals with this profile generally process medications metabolized by the CYP2D6 enzyme at an expected rate. Please discuss any medication dosing concerns with your clinician or pharmacist.
This is the most common genotype globally, carried by the vast majority of individuals across all major ancestral populations.
Reduced enzyme activity
This genotype includes one copy of the variant associated with the CYP2D6*41 allele, which is known to result in reduced enzyme function. You may metabolize certain medications more slowly than average, 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 approximately 1 in 6 to 1 in 10 people of European ancestry, but is significantly less common in African and Asian populations.
Decreased enzyme activity
This genotype consists of two copies of the variant associated with the CYP2D6*41 allele, which is linked to decreased CYP2D6 enzyme activity. This may lead to slower metabolism of specific drugs, potentially resulting in higher plasma concentrations of those medications. Always discuss your genetic profile and any medication dosing with your clinician or pharmacist.
This genotype is relatively rare, occurring in a small percentage of the population, primarily observed in individuals of European descent.
What is rs601715?
The rs601715 variant is a single-nucleotide polymorphism (SNP) located within the CYP2D6 gene. In the context of pharmacogenomics, this specific SNP serves as a defining marker for the CYP2D6*41 allele. The CYP2D6 gene provides instructions for creating an enzyme that plays a critical role in breaking down, or metabolizing, a wide array of substances, including many commonly prescribed medications. When a person carries the *41 allele, the resulting enzyme may function less efficiently than the standard version. Because this variant is a key component of the *41 haplotype, identifying it through genetic testing helps researchers and clinicians categorize an individual's potential metabolic profile. It is important to note that rs601715 is just one piece of a complex genetic puzzle, as the CYP2D6 gene is highly polymorphic, meaning it contains many different variations that can collectively influence how a person processes drugs.
The Role of the CYP2D6 Gene
The CYP2D6 gene encodes the cytochrome P450 2D6 enzyme, which is primarily expressed in the liver. This enzyme is responsible for the metabolism of approximately 25% of all clinically used drugs, including antidepressants, antipsychotics, beta-blockers, and certain pain medications. Because of its broad influence, variations in this gene can lead to significant differences in how patients respond to treatment. Individuals are typically classified into metabolic phenotypes—such as poor, intermediate, normal, or ultrarapid metabolizers—based on the combined activity of their two inherited gene copies. The *41 allele, marked by rs601715, is classified as a reduced-function allele. This means that individuals carrying this variant may process certain medications more slowly than those with fully functional alleles. Understanding these metabolic differences is the foundation of pharmacogenomics, a field dedicated to tailoring medical treatments to an individual's unique genetic makeup to optimize therapeutic outcomes and minimize adverse drug reactions.
Research and Clinical Evidence
Research into rs601715 and the *41 allele has evolved significantly over the last decade. While the association between this variant and reduced enzyme activity is well-documented, the clinical evidence regarding its exact impact on specific drug dosing remains nuanced. Expert consensus groups, such as the Clinical Pharmacogenetics Implementation Consortium (CPIC), have historically assigned activity scores to these alleles to help guide clinical decisions. Recent studies have suggested that the actual impact of the *41 allele on enzyme activity might be even lower than previously estimated, leading to updates in how these variants are categorized. Because the evidence strength for this specific variant is considered limited in some clinical contexts, it is rarely used in isolation to make major medical decisions. Instead, it is viewed as part of a broader assessment of a patient's total CYP2D6 genotype. If you are concerned about how your genetics might affect your medication, it is essential to discuss these results with your healthcare provider or a clinical pharmacist who can interpret them in the context of your specific health history.
Population Frequency
The frequency of the rs601715 variant varies significantly across different global populations. In European populations, the minor allele frequency is typically observed between 0.08 and 0.12. This makes the *41 allele a relatively common contributor to reduced CYP2D6 function in these groups. Conversely, the frequency of this specific variant is generally lower in populations of African and Asian ancestry, where other CYP2D6 variants, such as *10 or *17, may be more prevalent. These differences highlight the importance of considering ancestral background when interpreting genetic data. Because genetic diversity is high, the presence of the *41 allele does not guarantee a specific clinical outcome, as other genetic and environmental factors—such as diet, age, and other medications—also play a major role in how the body processes drugs. Genetic testing provides a snapshot of potential metabolic capacity, but it is only one tool among many used by clinicians to ensure safe and effective patient care.
What You Can and Cannot Do
If you have received genetic testing results indicating the presence of rs601715, it is important to understand the limitations of this information. You cannot use this data to diagnose a medical condition or to independently adjust your medication dosages. Self-adjusting medication based on genetic reports can be dangerous and may lead to ineffective treatment or serious side effects. What you can do is use this information as a starting point for a conversation with your doctor. Bring your report to your next appointment and ask how your genetic profile might influence the medications you are currently taking or may need in the future. A healthcare professional can evaluate your entire genetic profile, your current health status, and your medication list to determine if any adjustments are necessary. Remember that pharmacogenomic testing is a supportive tool, not a replacement for professional medical judgment. Always consult with a qualified clinician before making any changes to your prescribed treatment plan.
How common is this variant?
The rs601715 variant has a minor allele frequency of approximately 0.08 to 0.12 in European populations, with lower frequencies observed in African and Asian ancestries.
Frequently asked questions
Does having the rs601715 variant mean I am a poor metabolizer?
Not necessarily. The rs601715 variant is associated with reduced function, but your overall metabolic status depends on the combination of both copies of your CYP2D6 gene. A clinician must look at your full diplotype to determine if you are a poor, intermediate, or normal metabolizer.
Can I use this genetic information to change my medication dose?
No. You should never change your medication dosage based on genetic test results without consulting your doctor. Genetic data is only one factor in determining the right dose, and changing it yourself could lead to serious health risks.
Is rs601715 the only variant that affects CYP2D6?
No, the CYP2D6 gene is highly complex with many different variants. There are dozens of known alleles, and rs601715 is just one specific marker used to identify the *41 allele.
Where can I find more information about my specific genotype?
You should discuss your specific genetic report with your primary care physician or a clinical pharmacist. They can provide context based on your medical history and current medications.
Sources & further reading
Educational information only, last refreshed 9/17/2026. 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.
Promoter variant defining the CYP2D6*41 allele, associated with reduced enzyme expression and decreased metabolic capacity for various drugs.
Defines the non-functional CYP2D6*41 splice defect associated with intermediate metabolizer phenotype affecting codeine, tamoxifen, and SSRI metabolism.