CYP2D6 rs5758550: What Your Genotype Means
The rs5758550 variant is a single nucleotide polymorphism located downstream of the CYP2D6 gene. It is frequently studied for its potential role as an enhancer that may influence the expression and activity of the CYP2D6 enzyme, which is responsible for metabolizing many clinical medications.
What each genotype means
Enhanced CYP2D6 expression
This genotype is associated with increased full-length CYP2D6 protein expression in liver tissue. Research suggests this variant acts as an enhancer, though its effect on drug metabolism depends on the specific CYP2D6 star allele haplotype it is linked to. Please discuss any medication dosing concerns with your clinician or pharmacist.
Commonly observed in European and African ancestry populations.
Variable CYP2D6 expression
This genotype represents a heterozygous state where one copy of the gene carries the enhancer variant and the other does not. The overall impact on CYP2D6 enzyme activity is complex and varies based on the specific star alleles present on each chromosome. Please discuss any medication dosing concerns with your clinician or pharmacist.
Commonly observed in European and African ancestry populations.
Baseline CYP2D6 expression
This genotype lacks the enhancer variant associated with increased CYP2D6 protein expression. Your enzyme activity levels will be primarily determined by your inherited CYP2D6 star alleles rather than this specific enhancer site. Please discuss any medication dosing concerns with your clinician or pharmacist.
Commonly observed in European and African ancestry populations.
Understanding the Variant and Its Location
The rs5758550 variant is a genetic marker situated approximately 116 kilobases downstream of the CYP2D6 gene locus. Because of this significant physical distance, researchers often refer to it as a distal enhancer. In the context of genomics, an enhancer is a regulatory DNA sequence that can increase the transcription of a target gene. While many variants are located directly within the coding regions of a gene, rs5758550 sits in a non-coding region, making its functional relationship with the CYP2D6 gene complex to map. Scientists use computational phasing and large-scale population studies to determine how this variant links to specific CYP2D6 star alleles, which are the standard nomenclature used to describe different functional versions of the gene. Because it is not located within the gene itself, its influence on protein production is indirect and remains a subject of ongoing investigation in the field of pharmacogenomics.
The Role of the CYP2D6 Gene
The CYP2D6 gene provides instructions for making an enzyme that belongs to the cytochrome P450 family. This enzyme is primarily expressed in the liver and is responsible for the metabolism of approximately 25% of all clinically used drugs, including antidepressants, antipsychotics, and pain medications. Because the CYP2D6 gene is highly polymorphic, meaning it has many different variations, individuals can have vastly different capacities to process these medications. Some people are 'ultrarapid metabolizers' who break down drugs very quickly, while others are 'poor metabolizers' who process them very slowly. Understanding these variations is critical for clinicians, as it helps in predicting how a patient might respond to a specific drug or dose. When a patient's metabolism is either too fast or too slow, it can lead to therapeutic failure or an increased risk of adverse drug reactions, making the study of regulatory variants like rs5758550 essential for precision medicine.
Research Associations and Evidence Strength
Research into rs5758550 has yielded mixed results regarding its clinical utility. Some studies have suggested that the 'G' allele of this variant is associated with increased CYP2D6 expression and may help refine the prediction of enzyme activity when combined with other known markers. However, other investigations have found that the impact of this variant on drug clearance is modest or inconsistent across different substrates. A major challenge in this research is that rs5758550 is in high linkage disequilibrium with many other SNPs, meaning it is often inherited alongside other genetic changes, making it difficult to isolate its specific effect. Consequently, the evidence strength for using this variant in routine clinical testing is currently considered moderate. Many experts argue that there is not yet sufficient evidence to warrant its inclusion in standard clinical pharmacogenetic panels, as its contribution to predicting patient outcomes remains secondary to established star allele definitions.
Clinical Implications and Patient Guidance
It is important to understand that genetic variants like rs5758550 are tools for statistical research rather than diagnostic markers for individual health outcomes. While scientists study these markers to improve our understanding of drug metabolism, they do not provide a complete picture of how your body will respond to a specific medication. Factors such as age, liver function, diet, and other concurrent medications also play significant roles in drug processing. If you have received information about your CYP2D6 genotype, it is essential to discuss these results with your healthcare provider or a clinical pharmacist. They are the only ones qualified to interpret how your specific genetic profile might influence your treatment plan. Never make changes to your prescribed medications based on genetic test results without consulting your clinician, as they will consider your entire medical history to ensure your treatment is safe and effective.
How common is this variant?
The rs5758550 variant is commonly observed in both European and African ancestry populations, with the 'G' allele occurring at varying frequencies across different global groups.
Frequently asked questions
Is rs5758550 a diagnostic test for drug metabolism?
No, rs5758550 is a research-level genetic marker. It is not used as a standalone diagnostic test to determine how you will metabolize medications.
Should I change my medication based on this variant?
Absolutely not. You should never change your medication dosage or stop taking a prescribed drug based on genetic test results without consulting your doctor.
Why is this variant called an enhancer?
It is called an enhancer because some research suggests it may increase the expression of the CYP2D6 gene, though this effect is not fully confirmed in all clinical settings.
Where can I find more information on CYP2D6 testing?
You can speak with your primary care physician or a genetic counselor. They can provide context on whether pharmacogenetic testing is appropriate for your specific medical needs.
Sources & further reading
Educational information only, last refreshed 11/8/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Get my report — $29Related variants in CYP2D6
This missense variant (A237S) is a known marker used in the definition of specific CYP2D6 star alleles, which influence the metabolism of various drugs including antidepressants and opioids.
This stop-gain variant (R378X) results in a non-functional CYP2D6 enzyme, contributing to a poor metabolizer phenotype that necessitates dosage adjustments for affected medications.
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.