CYP2C19 rs72558184: Understanding the *35 Allele
The rs72558184 variant is a specific genetic marker within the CYP2C19 gene that defines the *35 allele. It is associated with decreased metabolic clearance of certain medications, such as clopidogrel and voriconazole, which are processed by the CYP2C19 enzyme.
What each genotype means
Normal enzyme activity
This genotype represents the most common form of the CYP2C19 gene, often referred to as the *1/*1 diplotype. Individuals with this profile typically exhibit normal metabolic clearance of CYP2C19 substrates like clopidogrel and voriconazole. Please discuss any medication dosing or treatment strategies with your clinician or pharmacist.
This is the most common genotype globally, found in the vast majority of the population.
Decreased enzyme activity
This genotype includes the *35 allele, which is associated with decreased metabolic clearance of certain medications. Research indicates that carriers may process drugs like clopidogrel or voriconazole differently than those without this variant. Because the clinical impact of this specific allele is considered limited, you should consult your healthcare provider to determine if this information is relevant to your current treatment plan.
This genotype is rare globally, with a frequency of less than 0.005, and is observed most frequently in African-American and Latino populations.
Reduced enzyme activity
Carrying two copies of this variant may result in further reduced metabolic capacity for CYP2C19 substrates compared to individuals without the variant. While the *35 allele is linked to decreased clearance, the overall clinical significance remains an area of ongoing study. Always discuss your genetic results and any potential impact on medication efficacy with your doctor or pharmacist.
This homozygous genotype is extremely rare in the general population.
What is rs72558184?
The rs72558184 variant is a single nucleotide polymorphism (SNP) located within the CYP2C19 gene on chromosome 10. In the context of pharmacogenomics, this specific variant is used to identify the CYP2C19*35 allele. Genetic variants like this are essentially "spelling differences" in the DNA sequence that can alter how an individual's body produces specific proteins. Because CYP2C19 is a critical enzyme for breaking down various drugs, changes in its genetic code can lead to differences in how quickly or effectively a person metabolizes those medications. Researchers track these variants to better understand why individuals may respond differently to the same standard dose of a prescribed drug.
The Role of the CYP2C19 Gene
The CYP2C19 gene provides instructions for making an enzyme that belongs to the cytochrome P450 family. These enzymes are primarily found in the liver and are responsible for the metabolism of a wide range of substances, including many common clinical drugs. By chemically modifying these drugs, the CYP2C19 enzyme helps the body clear them from the system. When a variant like *35 is present, it may result in a nonfunctional or reduced-function enzyme. This can lead to slower clearance of "substrate" drugs—medications that rely on this enzyme to be activated or deactivated. If a drug is not processed correctly, it may stay in the bloodstream longer than intended or fail to reach its therapeutic target.
Research and Clinical Evidence
The evidence linking rs72558184 to clinical outcomes is currently considered limited. While the *35 allele is characterized by decreased metabolic clearance of substrates like clopidogrel and voriconazole, it is not as widely studied as more common variants like *2 or *3. Research indicates that this is an intronic polymorphism, meaning it sits in a non-coding region of the gene, yet it still influences the enzyme's function. Because the clinical impact of this specific variant is still being defined, it is not always included in standard, high-throughput pharmacogenetic panels. Clinicians and researchers continue to investigate how this variant interacts with other genetic factors to influence drug response in diverse patient populations.
Population Frequency
The rs72558184 variant is considered rare on a global scale, with an overall population frequency of less than 0.005. However, genetic frequency can vary significantly based on ancestry. Current data suggests that this variant is observed most frequently in African-American and Latino populations. Because it is rare, many individuals will not carry this specific allele. Understanding the distribution of such variants is important for researchers who aim to ensure that pharmacogenetic studies and clinical guidelines are representative of the global population, rather than focusing solely on groups where a variant might be more common.
Navigating Your Genetic Information
If you have received information about your CYP2C19 genotype, it is important to remember that genetic testing is only one piece of the puzzle. Factors such as age, liver function, diet, and other medications you are taking also play a significant role in how your body processes drugs. You should never use genetic information to make decisions about your health or medication regimen on your own. If you are concerned about how a medication might affect you, or if you have questions about your genetic test results, please discuss them with your clinician or a pharmacist. They are the best resources to help you interpret these findings in the context of your overall medical history and current treatment plan.
How common is this variant?
The rs72558184 variant is rare globally, with a frequency of less than 0.005, though it is observed more frequently in African-American and Latino populations.
Frequently asked questions
What does it mean to be a CYP2C19 poor metabolizer?
A poor metabolizer has two non-functional copies of the CYP2C19 gene. This means they process certain drugs much slower than average, which may require a doctor to adjust the dosage or choose a different medication.
Is rs72558184 the same as the *2 allele?
No, rs72558184 defines the *35 allele, while the *2 allele is defined by a different genetic marker (rs4244285). Both are associated with reduced enzyme function, but they are distinct genetic variants.
Should I get tested for CYP2C19 variants?
Pharmacogenetic testing is usually recommended by a doctor if you are prescribed a medication known to be affected by these genes, such as clopidogrel. You should discuss the necessity of testing with your healthcare provider.
Can I change my CYP2C19 genotype?
No, your genotype is inherited from your parents and remains the same throughout your life. While you cannot change your genes, your doctor can adjust your medical treatment based on your genetic profile.
Sources & further reading
Educational information only, last refreshed 9/19/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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The CYP2C19*2 loss-of-function splicing defect results in impaired biotransformation of prodrugs including clopidogrel and altered clearance of proton pump inhibitors and select antidepressants.
Defines the CYP2C19*17 increased function allele, conferring rapid or ultrarapid metabolism for CPIC-actionable drugs including clopidogrel, PPIs, and SSRIs.
Variant in the CYP2C19 locus associated with altered metabolism of clopidogrel and proton-pump inhibitors.
Defines the CYP2C19*8 loss-of-function variant (c.358T>C, p.Trp120Arg) which results in no enzymatic activity and impaired metabolism of CYP2C19 substrates.
Defines the non-functional CYP2C19*3 null allele resulting from a premature stop codon, leading to poor metabolism of drugs such as clopidogrel, escitalopram, and proton pump inhibitors.
Defines the CYP2C19*4 allele caused by an ATG start codon alteration that abolishes translation, resulting in reduced or absent drug metabolism capacity.