cgp-39393 and Disease-Models--Animal

In an effort to evaluate pharmacologic agents for optimal anticoagulant prophylaxis in patients undergoing free tissue transfer, we evaluated the efficacy of desirudin (Canyon Pharmaceuticals, Hunt Valley, MD), a recombinant hirudin that acts as a direct thrombin inhibitor, using a rat model of microvenous thrombosis.. Randomized, blinded study using an in vivo rat model of microvenous failure.. Thirty-two rats received either desirudin or saline in a randomized, blinded fashion 30 minutes prior to performance of a standardized thrombogenic procedure on rat femoral veins. Bleeding time, vessel patency, and presence of clot within the anastomosis were subsequently assessed. Appropriate statistical analyses were then performed.. There was a significant increase in vessel patency in rats treated preoperatively with desirudin compared to controls receiving saline (96.9% vs. 53.1%, P < .001). In evaluating patent vessels for non-occluding clot, 41.2% of control rats had non-obstructive clot at the site of anastomosis, versus 3.2% of rats treated with desirudin (P = .002). Bleeding times were longer in desirudin-treated rats than those that received saline (7.17 +/- 3 minutes vs. 5.15 +/- 1.2 minutes, P = .027).. The use of preoperative desirudin increases the rate of microvascular anastomotic patency, decreases the occurrence of non-occluding clot, and increases bleeding time in an in vivo rat model, indicating potential efficacy in patients undergoing microvascular free tissue transfer.

Topics: Anastomosis, Surgical; Animals; Disease Models, Animal; Fibrinolytic Agents; Graft Survival; Hirudins; Male; Microcirculation; Microsurgery; Preoperative Care; Rats; Rats, Sprague-Dawley; Recombinant Proteins; Surgical Flaps; Thrombosis

1. We compared the direct thrombin inhibitor, desulfatohirudin (REVASC) and the indirect thrombin inhibitor, heparin, as adjuncts to thrombolytic therapy with reteplase in a canine model of coronary artery thrombosis. 2. Reteplase (BM 06.022) is a recombinant unglycosylated variant of human tissue-type plasminogen activator. Thrombus formation in anaesthetized open chest dogs was induced by electrical injury. Left circumflex coronary artery blood flow was monitored for 210 min with an electromagnetic flow probe. Twenty eight dogs were randomized to receive i.v. heparin (120 iu kg-1 bolus plus 80 iu kg-1 per h) or i.v. hirudin (2.0 mg kg-1 bolus plus 2.0 mg kg-1 per h) 10 min before thrombolysis preceded by i.v. acetylsalicyclic acid (20 mg kg-1) 5 min prior to anticoagulation. Every dog received an i.v. double bolus injection of 0.14 + 0.14 u kg-1 ( = 0.24 + 0.24 mg kg-1) reteplase, 30 min apart, 1 h after thrombus formation. 3. At comparable reperfusion rates (12 out of 12 vs. 15 out of 16 dogs), hirudin enhanced time to reperfusion (14.3 +/- 1.4 vs. 23.2 +/- 3.4 min; P < 0.05) and completely prevented reocclusion after reperfusion in contrast to heparin (0 out of 11 vs. 7 out of 11 dogs; P < 0.05). Coronary blood flow quality was improved by hirudin as shown by a higher maximum blood flow after reperfusion (130 +/- 14.3 vs. 83 +/- 9.3% of baseline; P < 0.05), a higher blood flow level at 20, 30, 40, and 50 min after onset of thrombolysis (P < 0.05) and a longer cumulative patency time (195 +/- 1.7 vs. 166 +/- 12 min; P < 0.05). Activated partial thromboplastin time and buccal mucosa bleeding time were prolonged (P < 0.05) by either anticoagulant, but did not differ significantly between groups. 4. The direct thrombin inhibitor, desulfatohirudin, enhanced thrombolysis, prevented reocclusion and increased blood flow as compared with the indirect thrombin inhibitor, heparin, when investigated at one dose level each and used in conjunction with reteplase.

Topics: Animals; Coronary Circulation; Coronary Thrombosis; Disease Models, Animal; Dogs; Drug Therapy, Combination; Female; Fibrinolytic Agents; Half-Life; Heparin; Hirudin Therapy; Hirudins; Humans; Male; Plasminogen Activators; Recombinant Proteins; Thrombolytic Therapy; Tissue Plasminogen Activator

The effects of heparin boluses comparable with those commonly used during angioplasty procedures were compared with equal gravimetric doses of recombinant desulfatohirudin (CGP 39393) in a rabbit model of microarterial thrombosis. Seven-millimeter segments of the central arteries of the ears were isolated between microvascular clamps and subjected to arteriotomy and deep vessel wall trauma. Arteriotomies were closed with continuous 10-0 sutures. Five minutes before vascular reperfusion (opening of vascular clamps), boluses of heparin (1.00 mg/kg), hirudin (1.00 mg/kg), hirudin (0.25 mg/kg), or vehicle (saline) were administered to groups of 10 rabbits in a blind, random fashion. Neither agent prolonged arteriotomy bleeding times relative to vehicle. All active agents significantly increased patency rates versus vehicle at 30 minutes after reperfusion, though reduced vessel patency was noted in a substantial portion of vessels in the groups receiving 0.25 mg hirudin or 1.00 mg/kg heparin. Patency rates at 120 minutes were only improved by the 1.00 mg/kg hirudin dose, and in accord, thrombus weights were significantly reduced only by the 1.00 mg/kg dose of hirudin. In contrast, the anticoagulant response (measured as the activated partial thromboplastin time and anti-IIa and anti-Xa activities) was considerably more pronounced and of longer duration after administration of heparin and hirudin. This is consistent with the hypothesis that the inactivation of clot-bound thrombin that is produced by specific thrombin inhibition (hirudin) but not by cofactor-mediated thrombin inhibition (heparin) is of pivotal importance in achieving a profound and sustained antithrombotic effect following vascular trauma. While heparin boluses seem to be of doubtful value, hirudin seems a promising strategy in context with angioplasty procedures.

Topics: Animals; Disease Models, Animal; Female; Heparin; Hirudin Therapy; Hirudins; Male; Rabbits; Random Allocation; Recombinant Proteins; Thrombin; Thrombosis

An existing arterio-venous shunt thrombosis model in the rat has been modified to increase its usefulness for the testing of anti-thrombotic agents and characterised using morphological and radiometric techniques. The thrombus formed on the cotton thread held in the shunt was found to be composed of platelet aggregates surrounded by red thrombus. After 30 min of blood flow there was a 15-fold increase in the platelet content of the thrombus and a 4-fold increase in the fibrin(ogen) content compared with an equivalent weight of whole blood. Use of the anticoagulants recombinant desulphatohirudin (CGP 39393, 4 mg/kg, s.c.) and unfractionated heparin (800 IU/kg, s.c.) showed that approx. 90% inhibition of thrombus weight and approx. 80% inhibition of fibrin(ogen) content could be achieved without significant effect on the platelet content. Conversely, using the platelet inhibitor Iloprost (1 microgram kg-1 min-1), a reduction in thrombus weight of 50% was associated with 75% inhibition of platelet content and only 20% inhibition of fibrin(ogen). These observations suggest that the growth of this type of thrombus is largely the result of continued fibrin formation rather than continued platelet recruitment and activation.

Topics: Animals; Arteriovenous Shunt, Surgical; Disease Models, Animal; Fibrinolytic Agents; Hematologic Tests; Heparin; Hirudin Therapy; Hirudins; Iloprost; Male; Radiometry; Rats; Rats, Inbred Strains; Recombinant Proteins; Thrombosis

Various reactions of disseminated intravascular coagulation (DIC) were experimentally induced by infusion of thrombokinase in rats, by administration of endotoxin in rabbits and pigs and by infusion of adrenaline and thrombin in dogs. Low plasma concentrations of recombinant hirudin (r-hirudin; 20-200 ng/ml) were sufficient for the inhibition of the different triggering mechanisms. The studies on the pharmacological profile of r-hirudin in DIC therapy confirm the efficacy of this specific tight-binding thrombin inhibitor.

Topics: Animals; Disease Models, Animal; Disseminated Intravascular Coagulation; Dogs; Endotoxins; Epinephrine; Factor Xa; Factor Xa Inhibitors; Female; Fibrinolytic Agents; Hemodynamics; Hirudin Therapy; Hirudins; Lipid A; Male; Platelet Count; Rabbits; Rats; Rats, Inbred Strains; Recombinant Proteins; Species Specificity; Swine; Thrombin; Thrombolytic Therapy; Thrombosis; Viscera