Mechanisms of variability in antiplatelet agents response

Inter-individual variability in the response to antiplatelet drugs has been reported. Suboptimal response to aspirin, as determined by specific tests, is rare and, in most instances, caused by poor compliance. In contrast, it is well established that the pharmacological response to clopidogrel is widely variable, with a significant proportion of subjects (about 1/3) being very poor responders. Inter-individual difference in the extent of metabolism of clopidogrel to its active metabolite is the most plausible mechanism for the observed inter-individual variability in platelet inhibition. Tailored treatment based on laboratory monitoring of platelet function has been proposed as a solution to poor responsiveness to clopidogrel. However, we still need to identify the ideal laboratory test and to answer basic questions on its clinical utility and cost-effectiveness, before monitoring clopidogrel therapy can be recommended in clinical practice.