A prodrug: it does nothing until an enzyme switches it on. People whose enzyme works poorly get less of the drug they were prescribed, and this is one of the few places where a guideline says to use a different medicine.
One of the few gene-drug pairs where a guideline names a different medicine. Clopidogrel is a prodrug — it does nothing until CYP2C19 converts it into the molecule that actually keeps platelets from clumping. People carrying no-function alleles (CYP2C19*2 and *3 are the common ones) make less of that active metabolite, and CPIC reports that intermediate and poor metabolisers on clopidogrel have reduced platelet inhibition and a higher risk of major adverse cardiovascular and cerebrovascular events. Where an alternative antiplatelet is not contraindicated, CPIC recommends using one. The 2022 update strengthened the recommendation for intermediate metabolisers and widened the indications it covers. This is a conversation for the cardiologist who prescribed it, not a reason to stop taking anything: stopping an antiplatelet after a stent is dangerous in a way this genotype is not.
CPIC Guideline for CYP2C19 Genotype and Clopidogrel Therapy: 2022 Update, Clinical Pharmacology & Therapeutics (PMID 35034351)
These are the positions in your own file that carry the genes above. Not every gene in a guideline is one we report — where that is the case the gene appears above without a variant here, and the note says so.
CYP2C19 · rs35013847
Read more →CYP2C19 · rs4244285
Read more →CYP2C19 · rs4986893
Read more →CYP2C19 · rs12248560
Read more →