CYP2D6 rs3892097: Understanding the *4 Loss-of-Function Variant
The rs3892097 variant is a well-studied genetic change in the CYP2D6 gene that significantly reduces the activity of a critical drug-metabolizing enzyme. It is the defining marker for the CYP2D6*4 allele, which is associated with a decreased ability to process various medications, potentially impacting drug efficacy and safety.
What each genotype means
Normal enzyme activity
This genotype is associated with normal function of the CYP2D6 enzyme, which is responsible for metabolizing many common medications. Individuals with this profile typically process drugs at an expected rate, though other genetic factors can still influence metabolism. Please discuss any medication concerns or side effects with your healthcare provider or pharmacist.
This is the most common genotype in most global populations, though frequencies vary significantly by ancestry.
Reduced enzyme activity
This genotype indicates you carry one copy of the variant associated with the CYP2D6*4 allele, which can lead to reduced enzyme activity. Research suggests this may affect how your body processes certain antidepressants or other medications, potentially altering their efficacy or side effect profile. Always consult your clinician before making changes to your prescribed medication regimen.
Carried by a significant portion of individuals of European ancestry, where the T allele frequency is approximately 15-20%.
Deficient enzyme activity
This genotype means you carry two copies of the variant associated with the CYP2D6*4 allele, which is linked to a significant loss of enzyme function. Studies have shown that individuals with this profile may experience an increased risk of side effects or reduced therapeutic response when taking certain medications, such as specific tricyclic antidepressants. It is important to discuss this genetic information with your doctor or pharmacist to ensure your treatment plan is appropriate for your metabolism.
This genotype is less common than the heterozygous form, occurring in a smaller percentage of the population, primarily within European groups.
What is rs3892097?
The rs3892097 variant is a single nucleotide polymorphism (SNP) located within the CYP2D6 gene on chromosome 22. In scientific literature, this specific change is often referred to as 1846G>A. This genetic variation is the primary defining feature of the CYP2D6*4 allele, which is widely recognized in pharmacogenomics as a 'no-function' allele. When this variant is present, it disrupts the normal splicing process of the gene's messenger RNA, leading to the production of a non-functional or unstable enzyme. Because the CYP2D6 enzyme is responsible for breaking down a vast array of therapeutic drugs, the presence of this variant can significantly alter how an individual processes these substances. Understanding this variant is a cornerstone of personalized medicine, as it helps researchers and clinicians identify why some people may experience different responses to standard medication dosages compared to others.
The Role of the CYP2D6 Gene
The CYP2D6 gene provides instructions for making an enzyme that belongs to the cytochrome P450 family. These enzymes are primarily found in the liver and are essential for the metabolism of approximately 25% of all clinically used drugs. CYP2D6 is particularly important because it processes a wide variety of medications, including antidepressants, antipsychotics, opioids like codeine, and the breast cancer treatment tamoxifen. Because the gene is highly polymorphic—meaning it has many different versions or alleles—individuals can have varying levels of enzyme activity. Some people are 'extensive' or 'normal' metabolizers, while others may be 'poor' metabolizers if they carry two non-functional alleles like *4. In the case of prodrugs, such as codeine, the enzyme is required to convert the medication into its active form. Consequently, individuals with reduced CYP2D6 activity may not receive the intended therapeutic benefit from these specific types of drugs.
Research and Clinical Associations
Extensive research has linked the rs3892097 variant to significant changes in drug metabolism. Clinical annotations from databases like PharmGKB and ClinVar highlight its role in the poor metabolism of drugs such as debrisoquine, various tricyclic antidepressants, and tamoxifen. The evidence for this association is considered strong, as the *4 allele is one of the most frequently studied markers in pharmacogenomics. Studies have shown that patients carrying this variant may require dosage adjustments to avoid toxicity or to ensure the drug reaches effective levels in the bloodstream. However, it is important to note that drug response is complex and can be influenced by other factors, including drug-drug interactions, age, and overall health. Because of this, genetic testing results should always be interpreted by a qualified healthcare professional who can integrate this information into a broader clinical context.
What You Can Do With This Information
If you have information about your CYP2D6 genotype, it is essential to use it as a tool for conversation with your doctor or pharmacist. This data is not a diagnosis and does not predict your health outcomes in isolation. Instead, it provides a piece of the puzzle that can help your clinician make more informed decisions about medication selection and dosing. You should never change or stop taking a prescribed medication based on genetic test results without consulting your healthcare provider. If you are concerned about how your body processes a specific drug, ask your doctor if pharmacogenomic testing is appropriate for your situation. They can help determine if your genetic profile warrants a change in therapy or a different dosage strategy. Always prioritize professional medical advice over self-interpretation of genetic data.
How common is this variant?
The rs3892097 variant is common in European populations, where the *4 allele frequency is approximately 15-20%.
Frequently asked questions
Does having the rs3892097 variant mean I am allergic to my medication?
No, this variant is not an allergy. It relates to how quickly or efficiently your liver enzymes break down a drug, which can affect whether the medication is effective or if it builds up to levels that cause side effects.
Can I change my CYP2D6 genotype?
No, your genotype is inherited from your parents and remains the same throughout your life. However, your 'phenotype'—or how you actually metabolize drugs—can sometimes be affected by other medications you take, a process known as phenoconversion.
Should I get tested for this variant before taking antidepressants?
Pharmacogenomic testing is becoming more common, but it is not required for everyone. You should discuss with your psychiatrist or primary care physician whether testing is appropriate based on your medical history and the specific medications being considered.
Is rs3892097 the only variant that affects CYP2D6?
No, the CYP2D6 gene is highly polymorphic, meaning there are many different variants that can affect enzyme activity. The *4 allele is just one of many, and clinical labs often test for a panel of common variants to get a complete picture.
Sources & further reading
Educational information only, last refreshed 9/16/2026. 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.
This variant defines the CYP2D6*29 star allele, contributing to the complex phenotype of drug metabolism for substrates like antidepressants and opioids.
This variant is associated with altered metabolism of various medications, including antidepressants and antipsychotics.
This SNP is a well-established marker for reduced enzyme activity, impacting drug clearance rates.
This variant is associated with altered metabolism of various medications, including antidepressants and antipsychotics.