Clopidogrel resistance

Clopidogrel resistance

Some patients may be poor metabolizers of clopidogrel in that they do not effectively convert it into active form because of low CYP2C19 activity causing a reduced effectiveness (clopidogrel resistance). This can be checked by evaluating the CYP2C19 status of the individual. Alternative dosing regimens or another antiplatelet agent may be used if clopidogrel resistance is present due to poor metabolism of the drug. Even though a higher dose regimen (600 mg loading dose followed by 150 mg once daily) improves the antiplatelet effect in poor metabolizers an ideal dose regimen for such individuals is yet to be established based on clinical outcomes trial. It may be noted that the CYP2C19*1 allele has fully functional metabolism of clopidogrel while CYP2C19*2 and *3 alleles have no functional metabolism of the drug. These two contribute to the majority of the poor clopidogrel metabolizers. CYP2C19*4, *5, *6, *7, and *8 may also be associated with absent or reduced clopidogrel metabolism, though they are less frequent than the CYP2C19*2 and *3 alleles .

Reference

  1. http://www.fda.gov/Drugs/DrugSafety/PostmarketDrugSafetyInformationforPatientsandProviders/ucm203888.htm