title: Combination of platelet fibrinogen receptor antagonist and direct thrombin inhibitor at low doses markedly improves thrombolysis.
abstract: BACKGROUND
  We evaluated the effects of a novel platelet fibrinogen receptor antagonist, Integrelin, and a direct thrombin inhibitor, recombinant hirudin, given together with recombinant tissue plasminogen activator (rTPA) in a canine experimental model of intracoronary thrombosis. We tested the hypothesis that combination of both agents at low doses would have an additive antithrombotic effect, resulting in a significant improvement in the efficacy of rTPA.
  
  
  RESULTS
  Thirty-two dogs with an electrically induced coronary thrombus were treated with rTPA (1 mg/kg over 20 minutes) together with one of the following adjunctive treatments in a random fashion. Eight dogs received saline for 90 minutes; Integrelin (5 micrograms.kg-1.min-1 for 90 minutes) was given to 8 dogs; 8 dogs received recombinant hirudin (20 micrograms.kg-1.min-1 for 90 minutes); and 8 dogs were treated with a low-dose combination of Integrelin (2.5 micrograms.kg-1.min-1) plus recombinant hirudin (10 micrograms.kg-1.min-1) for 90 minutes. Integrelin or recombinant hirudin, when given as single adjunct to rTPA, enhanced the lysis of the occlusive thrombus, causing full restoration of coronary blood flow (100% of its baseline value) for 29 +/- 16 and 26 +/- 5 minutes, respectively, whereas coronary blood flow was fully restored for only 5 +/- 1 minutes in dogs receiving rTPA plus saline (both P < .05). However, either Integrelin or recombinant hirudin failed to modify the reocclusion rate (57% and 63%, respectively) compared with saline (83%; all P = NS). Conversely, the low-dose combination therapy led to complete restoration of coronary blood flow for 92 +/- 19 minutes (P < .01 versus all treatments) and significantly reduced the reocclusion rate (25%; P < .05 versus saline).
  
  
  CONCLUSIONS
  These data show that inhibition of specific pathways of platelet and thrombin activity improves the extent and duration of rTPA-induced thrombolysis in the electrolytic canine model. Furthermore, our findings suggest that low doses of platelet IIb/IIIa and direct thrombin antagonists in combination may be used successfully during thrombolysis.
authors.affiliation: Department of Cardiology, Cleveland Clinic Foundation, OH 44195.
authors.forename: F A
authors.initials: FA
authors.lastname: Nicolini
authors.forename: P
authors.initials: P
authors.lastname: Lee
authors.forename: G
authors.initials: G
authors.lastname: Rios
authors.forename: K
authors.initials: K
authors.lastname: Kottke-Marchant
authors.forename: E J
authors.initials: EJ
authors.lastname: Topol
mesh_terms: D000818:Animals; D001777:Blood Coagulation / Q000187:drug effects; D003326:Coronary Circulation / Q000187:drug effects; D003328:Coronary Thrombosis / Q000188:drug therapy*; D004285:Dogs; D004359:Drug Therapy, Combination; D000077542:Eptifibatide; D005260:Female; D024764:Hirudin Therapy; D006629:Hirudins / Q000008:administration & dosage; D008297:Male; D010455:Peptides / Q000008:administration & dosage / Q000627:therapeutic use*; D010974:Platelet Aggregation / Q000187:drug effects; D010980:Platelet Membrane Glycoproteins / Q000037:antagonists & inhibitors*; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000627:therapeutic use; D015912:Thrombolytic Therapy / Q000379:methods*; D010959:Tissue Plasminogen Activator / Q000008:administration & dosage / Q000627:therapeutic use*
chemical_list: D006629:Hirudins; D010455:Peptides; D010980:Platelet Membrane Glycoproteins; D011994:Recombinant Proteins; D010959:Tissue Plasminogen Activator; D000077542:Eptifibatide