Clopidogrel Test

Clopidogrel is used to prevent strokes and heart attacks by preventing clot formation in the blood. Up to 30% of people do not respond to clopidogrel treatment and are regarded as being resistant to it. This drug has to be activated by conversion to another substance (prodrug ).  There are a number of enzymes known to be involved including CYP2C19, CYP2C9, CYP3A4, MDR1 and CYP3A5.

Several recent  clinical studies have shown that the only important enzyme  to test is CYP2C19. Testing CYP2C19 can identify those people where the drug does not work as well and they are at greater risk of heart attack and stroke. Ultrarapid metabolisers of CYP2C19 are likely to have higher blood concentrations of the active metabolite and may be more prone to bleeding events.

Co-medication is cautioned with drugs that interact with any of the pathways involved in the processing. Several drug-drug interactions have been published including severe ones involving the class of medications known as proton pump inhibitors.

A genetic test for CYP2C19 is recommended.