[Clopidogrel--clinical use and potential therapeutic problems]

Platelet activation is a major component in the pathogenesis of coronary thrombosis and myocardial infarction. Therefore, antiplatelet therapy has become the cornerstone in the therapy of ischemic heart disease. Thienopyridines, especially clopidogrel, have a highly significant effect on treated patients with regard to reduction of stent thrombosis and functional inhibition of adenosine diphosphate-(ADP-)induced platelet activation. Clopidogrel, a specific inhibitor of the P2Y(12) ADP receptor, is a prodrug which releases the active compound after metabolization. Actual ACC/AHA/SCAI guidelines recommend the use of 75 mg clopidogrel once daily after stent implantation. Nevertheless, there is a high incidence of impaired clopidogrel responsiveness in patients potentially leading to subacute stent thrombosis and other adverse cardiovascular events following coronary interventions (incidence of about 1% within the first 4 weeks). Therefore, individual risk testing and adjusted antiplatelet therapy might be recommendable under certain circumstances, e.g., high-risk interventions such as last patent vessel, dominant vessel, or planned drug-eluting stent implantation. Furthermore, identification of a nonresponder requires increased clinical attention. Newly developed antiplatelet substances might overcome the nonresponse problem and allow sufficient platelet inhibition in all patients. Further prospective studies are needed to determine the risk reduction by an individually adjusted antiplatelet therapy.