Defining the role of platelet glycoprotein receptor inhibitors in STEMI: focus on tirofiban.

Tirofiban is a small molecule, nonpeptide tyrosine derivative. Although similar to abciximab in that it has a high specificity and affinity for the glycoprotein (GP) IIb/IIIa receptor, tirofiban dissociates from the GP IIb/IIIa receptor more rapidly than abciximab. Additionally, the action of tirofiban is reversed within hours after completion of the infusion, whereas abciximab binds irreversibly resulting in a considerably longer effect. The efficacy of tirofiban in ST-segment elevation myocardial infarction (STEMI) has been demonstrated when administered in patients being managed with primary percutaneous coronary intervention (PCI). These trials primarily studied tirofiban utilizing the high-dose bolus regimen (25 microg/kg bolus followed by a maintenance infusion of 0.15 microg/kg/min for 18-24 hours). The On-TIME (Ongoing Tirofiban in Myocardial Infarction Evaluation) 2 trial assessed early administration of the high-dose bolus regimen of tirofiban either at the referral centre or in the ambulance, in patients being transferred to a primary PCI centre. Early use of tirofiban resulted in both a significant increase in the rate of complete resolution of ST-segment deviation pre- and post-PCI, and improvement in clinical outcomes at 30 days. Moreover, the multi-factorial MULTISTRATEGY (Multicentre Evaluation of Single High-Dose Bolus Tirofiban vs Abciximab With Sirolimus-Eluting Stent or Bare Metal Stent in Acute Myocardial Infarction) trial, which compared the high-dose bolus regimen of tirofiban with standard dose administration of abciximab administered immediately prior to PCI, revealed similar effects on myocardial perfusion, ST-segment elevation recovery and clinical outcomes between the two agents, and confirmed the safety of tirofiban when used in combination with drug-eluting stents in patients with STEMI undergoing primary PCI. These studies showed tirofiban to be a well tolerated and effective GP IIb/IIIa inhibitor. On the basis of the demonstrated benefits of the high-dose bolus regimen, tirofiban may be considered useful in the management of patients with STEMI.