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CYP2C19 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

CYP2C19 gene

The CYP2C19 gene produces an enzyme critical for metabolizing many common medications, including the antiplatelet drug clopidogrel.

Normal Function

The CYP2C19 gene is a member of the cytochrome P450 gene family, which is involved in the metabolism of various molecules within cells. The CYP2C19 enzyme is found primarily in the liver and is responsible for processing at least 10 percent of commonly prescribed drugs.

A key function of this enzyme is the conversion of clopidogrel (Plavix) into its active form. Active clopidogrel inhibits the P2RY12 receptor on the surface of platelets. By blocking this receptor, the drug prevents platelets from sticking together (aggregating) to form blood clots, which helps seal off damaged blood vessels.

Health Conditions Related to Genetic Changes

Clopidogrel resistance

Variations (polymorphisms) in the CYP2C19 gene can lead to clopidogrel resistance, where the drug is less effective than normal. These polymorphisms decrease the enzyme's ability to activate the drug.

  • Intermediate Metabolizers: Individuals with one copy of the normal CYP2C19*1 gene and one copy of a nonfunctional variant (CYP2C19*2 or CYP2C19*3) have a reduced ability to convert clopidogrel.
  • Poor Metabolizers: Individuals with two copies of the nonfunctional CYP2C19*2 or CYP2C19*3 variants can convert very little or none of the drug.

In these individuals, the P2RY12 receptor is not properly inhibited, allowing platelets to continue forming clots. This can increase the risk of heart attacks, strokes, and thromboses. However, individual response to the drug is also influenced by factors such as age, sex, weight, diet, and other medications.

Other disorders

Because the CYP2C19 enzyme metabolizes a wide range of drugs, genetic changes can affect the efficacy of other treatments, including proton pump inhibitors, antidepressants, anticonvulsants, hypnotics, sedatives, antimalarials, and antiretrovirals. While most changes lead to impaired metabolism, the CYP2C19*17 polymorphism increases the enzyme's activity, classifying individuals with two copies of this variant as ultra-rapid metabolizers.

Genomic Location

The CYP2C19 gene is found on chromosome 10.

Frequently Asked Questions

Clopidogrel can be replaced with ticagrelor or prasugrel, which do not rely on CYP2C19 for activation. These drugs are often preferred in patients with known poor metabolizer status or when clopidogrel resistance is suspected.
Individuals with two nonfunctional CYP2C19 alleles (*2 or *3) produce little or no active clopidogrel metabolite, leading to reduced platelet inhibition. This increases the risk of stent thrombosis, heart attack, or stroke after coronary procedures.
Testing is recommended before initiating clopidogrel in patients undergoing percutaneous coronary intervention, those with a history of clopidogrel resistance, or patients with risk factors for poor drug response (e.g., age >65, diabetes, or concurrent medications that inhibit CYP2C19).
Yes. Drugs that inhibit CYP2C19 (e.g., omeprazole, fluoxetine) can reduce clopidogrel activation, while inducers (e.g., rifampin) can increase it. Lifestyle factors such as smoking may also affect enzyme activity. Discuss all medications and supplements with your clinician to avoid interactions.===
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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