A randomized two-by-two comparison of high-dose bolus tirofiban versus abciximab and unfractionated heparin versus bivalirudin during percutaneous coronary revascularization and stent placement: the tirofiban evaluation of novel dosing versus abciximab with clopidogrel and inhibition of thrombin (TENACITY) study trial.

BACKGROUND: In the absence of high-dose thienopyridines, placebo-controlled trials have demonstrated a reduction in ischemic events with intravenous glycoprotein IIb/IIIa antagonists during percutaneous coronary intervention (PCI). One head-to-head trial comparing abciximab and tirofiban among PCI patients found tirofiban to be inferior, and laboratory evidence confirmed that the bolus dose of tirofiban tested in that trial to be less effective than abciximab. Whether a higher bolus dose of tirofiban would be as efficacious as abciximab during PCI is uncertain. METHODS AND RESULTS: Patients undergoing PCI were randomized equally to abciximab or to tirofiban, given as high-dose bolus (25 µg/kg) plus 12-hr infusion (0.15 µg/kg/min). All patients received aspirin and clopidogrel and were additionally randomized to unfractionated heparin or bivalirudin. Approximately 8,000 patients were to be studied, but after 383 were enrolled, the study sponsor discontinued the trial for financial reasons. The primary endpoint of 30-day death, myocardial infarction, or urgent target vessel revascularization occurred in 8.8% of patients randomized to abciximab and 6.9% of those randomized to tirofiban. The respective rates of major bleeding were 1.5 and 1.6%. Additionally, the primary endpoint occurred in 8.1% of patients randomized to unfractionated heparin and 7.6% of those randomized to bivalirudin. The respective rates of major bleeding were 2.5% and 0.5%. CONCLUSION: With limited assessment, this direct comparison of high-dose bolus tirofiban versus abciximab produced encouraging results and suggests that further study of this tirofiban dose regimen is warranted. The limited assessments comparing heparin and bivalirudin are consistent with prior observations.

Tirofiban as adjunctive therapy for acute coronary syndromes and percutaneous coronary intervention: a meta-analysis of randomized trials.

AIMS: To perform a thorough and updated systematic review of randomized clinical trials comparing tirofiban vs. placebo or vs. abciximab. METHODS AND RESULTS: We searched for randomized trials comparing tirofiban vs. placebo or any active control. Odds ratios (OR) were computed from individual studies and pooled with random-effect methods. Thirty-one studies were identified involving 20,006 patients (12 874 comparing tirofiban vs. heparin plus placebo or bivalirudin alone, and 7132 vs. abciximab). When compared with placebo, tirofiban was associated at 30 days with a significant reduction in mortality [OR = 0.68 (0.54-0.86); P = 0.001] and death or myocardial infarction (MI) [OR = 0.69 (0.58-0.81); P < 0.001]. The treatment benefit persisted at follow-up but came at an increased risk of minor bleedings [OR = 1.42 (1.13, 1.79), P = 0.002] or thrombocytopenia. When compared with abciximab, mortality at 30 days did not differ [OR = 0.90 (0.53, 1.54); P = 0.70], but in the overall group tirofiban trended to increase the composite of death or MI [OR = 1.18 (0.96, 1.45); P = 0.11]. No such trend persisted at medium-term follow-up or when appraising studies testing tirofiban at 25 microg/kg bolus regimen. CONCLUSION: Tirofiban administration reduces mortality, the composite of death or MI and increases minor bleedings when compared with placebo. An early ischaemic hazard disfavouring tirofiban was noted when compared with abciximab in studies based on 10 but not 25 microg/kg tirofiban bolus regimen.

Optimal platelet inhibition in patients undergoing PCI: data from the Multicenter Registry of High-Risk Percutaneous Coronary Intervention and Adequate Platelet Inhibition (MR PCI) study.

BACKGROUND: Optimal inhibition of platelet aggregation (IPA) may afford greater protection against ischemic events during percutaneous coronary intervention (PCI). The objective of this study was to test several antiplatelet regimens in elective high-risk PCI patients by comparing different combinations of glycoprotein IIb/IIIa inhibitors and clopidogrel. METHODS: The study was a randomized open-label study at 3 heart centers in India. One hundred twenty patients were enrolled between July 2006 and September 2006. Patients were randomized to 1 of the 4 groups: group A--tirofiban, group B--eptifibatide, group C--tirofiban + clopidogrel 600-mg loading dose, and group D--eptifibatide + clopidogrel 600-mg loading dose. All patients received a clopidogrel maintenance dose after PCI. The primary outcome measure was the IPA assessed at 10 minutes, at 6 to 8 hours, and at 24 hours. RESULTS: The IPA was higher with high-dose tirofiban compared with eptifibatide at 10 minutes (95.88 +/- 5.85% vs 91.22 +/- 7.52%, P = .003) and at 6 to 8 hours (93.11 +/- 7.6% vs 85.45 +/- 11.03, P < .001). Significantly more patients achieved >95% IPA with the high-dose tirofiban regimen. CONCLUSIONS: This head-to-head study comparing high-dose tirofiban with double-bolus eptifibatide demonstrated higher degree of platelet inhibition with high-dose tirofiban at 10 minutes and at 6 to 8 hours in patients undergoing elective high-risk PCI. The addition of clopidogrel did not acutely extend the IPA from intravenous glycoprotein IIb/IIIa inhibitors, but did so at 24 hours.

Glycoprotein IIb/IIIa antagonism and fibrinolytic therapy for acute myocardial infarction.

Fibrinolytic therapy for the treatment of ST-segment elevation myocardial infarction unquestionably reduces mortality when administered within 12 hours of symptom onset. By promptly restoring antegrade perfusion, infarct size is limited, ventricular function is less compromised, and mortality rates are lowered. Although fibrinolytic therapy initially restores antegrade flow in the infarct vessel in the majority of patients, sustained, tissue-level reperfusion occurs in only approximately one fourth of patients. Thrombin and platelets associated with a coronary thrombus are not specifically targeted by fibrinolytic agents, but rather have paradoxically increased activity. These components contribute to the tendency for vessel reocclusion after initially successful reperfusion. Thus, adjunctive therapy with antithrombins and antiplatelet agents are essential in the successful treatment of a coronary thrombus. Although aspirin has been shown to reduce mortality in acute myocardial infarction, it is a weak antiplatelet agent that is pathway specific. Glycoprotein IIb/IIIa inhibitors are potent antiplatelet agents that block the final common pathway for platelet aggregation. Thus, the growing evidence of platelet preeminence in the pathophysiology of failed thrombolysis has lead to the study of combination drug therapy with glycoprotein IIb/IIIa inhibition and reduced dose fibrinolytic agents in the treatment of acute ST-segment elevation myocardial infarction. This article reviews the rationale, results, and clinical implications of the major trials of combination drug therapy in acute myocardial infarction.