Platelet Monitoring and Interaction of Glycoprotein IIb/IIIa Antagonists with Other Antiplatelet Agents

Unlike other available antiplatelet agents, a clear dose-effect relationship for the platelet glycoprotein (GP) IIb/IIIa antagonists was well established in animal models prior to study in humans. Based on these early studies, a specific level of blockade of platelet GPIIb/IIIa receptors was identified as that necessary to prevent intraarterial thrombus formation, and this target level was carried forward into clinical trials. Subsequently, the efficacy of these agents in preventing thrombotic events has been confirmed in placebocontrolled trials involving nearly 50,000 patients (1,2). Despite these overall positive findings with GPIIb/IIIa receptor-blocker therapy, several large individual studies, in specific patient populations or with suboptimal dosing regimens, have found a lack of effect in preventing thrombotic complications (3,4). These results raise the question as to whether a specific dose of a GPIIb/IIIa antagonist, adjusted only by patient weight, can provide the same level of platelet inhibition across all clinical syndromes and across all individuals. If there is interindividual variability in response to standard dosing of GPIIb/IIIa antagonists, monitoring of platelet inhibition would allow for individualization of therapy and might improve the efficacy and safety of these agents.