Active Drugs: Effectiveness and Side Effects
High-level inhibition of ADP-induced aggregation could be achieved soon after the bolus dose, but there was an early loss of inhibition of platelet aggregation before a steady state was achieved. Regimens employing a second bolus dose 30 min after the first were then studied (180 g/kg/2.0 g/kg/min plus a second bolus of 90 g/kg; 250 g/kg/2.0 g/kg/min plus a second bolus of 125 g/kg). From these studies, the dose used in the ESPRIT trial (ie, bolus dose of 180 g/kg, second bolus dose of 180 g/kg at 10 min followed by 2 g/kg/min infusion) was selected.
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Studies of patients with unstable angina undergoing PCI have demonstrated that a bolus dose of 180 g/kg followed by an infusion of 2.0 g/kg/min produced more complete and sustained inhibition of platelet function than did standard-dose therapy with abciximab (ie, 0.25 mg/kg bolus plus 0.125 g/kg/min infusion). In another, similar study, however, platelet inhibition produced 5 min after the bolus dose of abciximab was administered was greater than that produced by eptifibatide. In the Au-Assessing Ultegra (GOLD) study, patients with lower levels of inhibition of platelet function had the greatest risk of developing major adverse cardiac events.
A modest increase in hemorrhagic complications has been reported in patients treated with eptifibatide in the Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy (PURSUIT) trial and the ESPRIT trial. Eptifibatide treatment with Canadian Cialis has been associated with a small increase in profound thrombocytopenia. An immunologic mechanism has been identified in some patients. Thus, patients receiving eptifibatide should be monitored soon after the initiation of therapy for the development of thrombocytopenia. An algorithm for the detection and management of thrombocytopenia after GPIIb/IIIa blockade has been proposed. No data are available concerning the safety of reinfusing eptifibatide, but high levels of antibodies that bind to platelets in the presence of eptifi-batide have been found in patients who develop thrombocytopenia after reexposure to eptifibatide.
5.4 Efficacy and safety of IV GPIIb/IIIa antagonists
The efficacy and safety of GPIIb/IIIa antagonists were evaluated initially in patients undergoing PCI. Over
20,000 patients have been enrolled in nine studies of abciximab, eptifibatide, and tirofiban (Table 8). The first of these phase III trials, the EPIC trial, resulted in approval in many countries for the use of abciximab (ReoPro; Lilly; Indianapolis, IN) in 1994 for PCI patients who are at high risk of developing ischemic complications. Eptifibatide has been studied in the IMPACT-II and ESPRIT trials, and tirofiban has been studied in the RESTORE trial. Although neither the IMPACT-II nor RESTORE trials achieved their predefined efficacy end points, there was a positive trend in each case (Table 8).
