Body and biology
What Is CYP2C19? The Clopidogrel Gene Enzyme Explained
CYP2C19 · say it: sip-TOO-see-nine-TEENAlso written: cytochrome P450 2C19, CYP2C19 enzyme, CYP2C19 genotype
Short answer
CYP2C19 is a liver enzyme that processes several medicines, including clopidogrel; how active it is depends partly on your genes.
What it means
CYP2C19 is one of the cytochrome P450 enzymes in the liver. It processes several commonly used medicines, including clopidogrel, many proton pump inhibitors (such as omeprazole), some antidepressants (such as citalopram) and the antifungal voriconazole. People inherit different versions of the CYP2C19 gene, so the enzyme works faster in some people and slower in others.
Clopidogrel labels carry a boxed warning about CYP2C19. Clopidogrel is a prodrug that needs CYP2C19 to be turned into its active form, so people who are poor metabolizers may get less protection from clots. Labels also warn that some medicines that block CYP2C19, such as omeprazole, can reduce clopidogrel's effect. Doctors may consider a gene test or a different antiplatelet.
CYP2C19 is separate from CYP3A4 and CYP2D6. A medicine can be affected by one, several or none of these enzymes.
Where you may see it
- Boxed warnings on clopidogrel labels
- Pharmacogenetic test reports
- The 'Drug interactions' section of PPI and antidepressant labels
📄 How it looks on a report
CYP2C19 genotype: *2/*2. Predicted phenotype: Poor metabolizer.
🙅 What it does not mean
- A CYP2C19 result is not a disease; it describes how you process some medicines.
- Being a poor metabolizer does not mean all medicines work less well for you; it depends on the medicine.
- Your result does not change over time, so keep a copy for future prescriptions.
🗒️ Questions to ask your doctor
💊 Medicines whose labels mention “CYP2C19”
Plain-English explanations of each medicine, from its official FDA label.
- Citalopram
a selective serotonin reuptake inhibitor (SSRI), a type of antidepressant medicine
- Clopidogrel
A platelet inhibitor of the P2Y12 type (a thienopyridine). It is a blood thinner that keeps platelets from sticking together.
🔗 Read more from trusted sources
- “CYP2C19” on MedlinePlus ↗
US National Library of Medicine
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