Superiority of enoxaparin over heparin in combination with a GPIIb/IIIa receptor antagonist during coronary thrombolysis in dogs

It is known that a low-molecular-weight heparin (LMWH) is more effective th an unfractionated heparin in unstable angina/non-Q-wave myocardial infarcti on (UA/NQMI) and the platelet GPIIb/IIIa receptors play an important role i n acute myocardial infarction (AMI). Therefore, enoxaparin might have a sim ilar advantage over heparin when used with a GPIIb/IIIa antagonist (RPR1098 91) in coronary thrombolysis. After induction of coronary thrombosis in ane sthetized dogs, infusion of saline, enoxaparin, heparin, RPR109891, enoxapa rin + RPR109891, or heparin + RPR109891 was initiated followed 15 min later by recombinant tissue plasminogen activator (rt-PA). The incidence of repe rfusion in the enoxaparin + RPR109891- and the heparin + RPR109891-treated groups was similar, but time to reperfusion tended to be shorter for enoxap arin versus heparin. Only 43% of the vessels reoccluded in the enoxaparin RPR109891 group, compared to 100% vessels in the heparin + RPR109891 group . Enoxaparin + RPR109891 maintained flow for a significantly longer time co mpared to saline, enoxaparin, heparin, and heparin + RPR109891. Enoxaparin + RPR109891 and heparin + RPR109891 increased the template bleeding time by 2- and 3-fold and activated partial thromboplastin time (APTT) by 1.3- and 3-fold, respectively. These data suggest that enoxaparin is more effective and potentially safer than heparin when combined with a GPIIb/IIIa recepto r antagonist during rt-PA-induced coronary thrombolysis. (C) 2001 Elsevier Science Ltd. All rights reserved.