CYP2D6 rs28371717: Understanding This Genetic Variant
The rs28371717 variant is a specific genetic change located within the CYP2D6 gene, which plays a critical role in how the body processes many medications. Current research associates this variant with normal enzyme function, though its impact can vary depending on an individual's overall genetic profile.
What each genotype means
Normal enzyme function
This genotype represents the most common form of the CYP2D6 gene at this position. Research indicates this variant is associated with normal enzyme function and typical drug metabolism. Please discuss any medication dosing or concerns with your clinician or pharmacist.
This is the most common genotype observed across most global populations.
Normal enzyme function
Carrying one copy of the T allele at this position is generally associated with normal CYP2D6 enzyme activity. Current evidence suggests this missense variant (A237S) does not significantly alter drug metabolism. Please discuss any medication dosing or concerns with your clinician or pharmacist.
This genotype is found at a low frequency in the general population.
Normal enzyme function
Carrying two copies of the T allele is associated with normal CYP2D6 enzyme function. While this variant is a known missense change, it is not considered to cause a significant loss or gain of metabolic activity. Please discuss any medication dosing or concerns with your clinician or pharmacist.
This genotype is rare in most populations.
What is rs28371717 and Where is it Located?
The variant rs28371717 is a single nucleotide polymorphism (SNP) situated on chromosome 22 within the CYP2D6 gene. In genetic terms, this variant represents a missense mutation, specifically identified as A237S, where a single amino acid change occurs in the resulting protein structure. Because the CYP2D6 gene is highly polymorphic—meaning it contains many different variations across the human population—researchers track specific SNPs like rs28371717 to better understand how these small changes influence the gene's overall performance. This particular variant is cataloged in major genomic databases, including dbSNP and gnomAD, which allow scientists to map its precise location and frequency across diverse ancestral groups. Understanding its position helps researchers determine if this specific change alters the enzyme's ability to interact with various chemical substrates, such as pharmaceutical drugs.
The Role of the CYP2D6 Gene
The CYP2D6 gene provides instructions for creating an enzyme that is a member of the cytochrome P450 family. This enzyme is primarily active in the liver and is responsible for the metabolism of approximately 20% to 25% of all clinically used medications. These include common drugs used for pain management, mental health conditions, and cancer treatment. Because CYP2D6 is so influential in drug processing, variations in this gene can lead to significant differences in how individuals respond to medication. Some people may metabolize drugs very quickly, while others may process them slowly, potentially leading to side effects or reduced therapeutic efficacy. The gene is known for its extreme diversity, with dozens of known alleles that can result in no function, decreased function, or normal function, making it a central focus of the field of pharmacogenomics.
Research Associations and Evidence Strength
Current evidence regarding rs28371717 suggests that it is associated with normal enzyme function. Unlike some other variants in the CYP2D6 gene that are classified as non-functional or having significantly reduced activity, rs28371717 is generally considered to maintain the enzyme's ability to metabolize its target substrates effectively. The evidence strength for this association is currently categorized as moderate. While many studies have investigated the broader landscape of CYP2D6, specific data on rs28371717 is often analyzed in the context of larger genotyping panels used to predict drug response. It is important to note that because CYP2D6 is so complex, the effect of any single variant can be masked or enhanced by other variations present on the same chromosome. Therefore, researchers emphasize that this variant should be viewed as one piece of a much larger, complex genetic puzzle.
Population Frequency and Variability
The frequency of the rs28371717 variant is known to be variable across different global populations. Genomic databases indicate that while the variant is present, its prevalence is not uniform, reflecting the diverse evolutionary history of the CYP2D6 gene. In some populations, the variant may be relatively rare, while in others, it may appear more frequently. This variability is a hallmark of the CYP2D6 gene, which has undergone significant selective pressure over time. Because of these differences, findings regarding the variant's frequency in one ancestral group cannot always be generalized to another. Researchers continue to collect data from diverse cohorts to better map these frequencies, which is essential for developing equitable pharmacogenomic tools that work accurately for people of all backgrounds.
What You Can and Cannot Do With This Information
Information about your genetic variants, such as rs28371717, is for educational purposes and should not be used to make personal medical decisions. While pharmacogenomic research is advancing, the clinical interpretation of a single SNP is rarely straightforward. Because drug metabolism is influenced by many factors—including other genetic variants, age, liver function, and other medications you may be taking—you should never change your medication dosage or stop taking a prescribed drug based on genetic test results. If you are curious about how your genetics might influence your response to a specific medication, the best course of action is to discuss this with your clinician or a pharmacist. They can interpret your results in the context of your full medical history and provide guidance on whether further testing or dosage adjustments are appropriate for your specific health needs.
How common is this variant?
The frequency of the rs28371717 variant is variable across different ancestral populations, with a global minor allele frequency reported at approximately 0.003 in major databases.
Frequently asked questions
Does rs28371717 mean I am a poor metabolizer?
No, current research associates the rs28371717 variant with normal enzyme function. It is not typically linked to the poor metabolizer phenotype.
Should I change my medication based on this result?
Absolutely not. You should never alter your medication regimen based on genetic information without consulting your doctor or pharmacist, as many factors influence drug response.
Is CYP2D6 testing standard for all drugs?
No, testing for CYP2D6 is only recommended for specific medications where genetic variation is known to significantly impact safety or efficacy. Your doctor will determine if such testing is necessary.
Where can I find more information about my CYP2D6 status?
You can discuss your genetic results with a healthcare provider or a genetic counselor. They can help you understand what your specific results mean for your health.
Sources & further reading
Educational information only, last refreshed 9/18/2026. 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.