Glycoprotein IIb/IIIa inhibitors: an update on the mechanism of action and use of functional testing methods to assess antiplatelet efficacy

The human glycoprotein (GP)IIb/IIIa belongs to a large family of cation-dependent adhesion molecules known as integrins, which share a common heterodimeric structure. The primary function of GPIIb/IIIa is to aid platelet aggregation by transmitting bidirectional signals across the plasma membrane. Since the GPIIb/IIIa receptor is among the key integrins involved in platelet aggregation and, therefore, thrombus formation, the development of GPIlb/Illa antagonists (e.g., abciximab, eptifibatide and tirofiban) has become an attractive strategy for antiplatelet therapy with an expected strong and specific effect. All three drugs are administered intravenously, and large-scale clinical trials have demonstrated a clear clinical benefit and good safety profile in high-risk patients, especially those undergoing percutaneous coronary intervention. However, the adverse events related to thrombosis or bleeding are still reported in patients undergoing therapy with GPIlb/Illa antagonists and reflect a variable interindividual responsiveness. Therefore, some form of laboratory monitoring is required to optimize the effects of a drug or to indicate that it needs replacing with other antithrombotic agents, as well as for identifying and enhancing the platelet inhibition in this subgroup of patients to improve the clinical outcome and reduce bleeding complications. As such, the aim of this article is to provide an update on the mechanism of action and use of functional testing methods to assess antiplatelet efficacy in patients undergoing therapy with GPIIb/IIIa antagonists.