The effects of doxazosin on platelet aggregation, platelet adhesion and blood coagulation in cynomolgus monkeys

Intraarterial reteplase and intravenous abciximab for treatment of acute ischemic stroke

We performed a preliminary feasibility and safety study using intravenous (IV) administration of a platelet glycoprotein IIb/IIIa inhibitor (abciximab) in conjunction with intraarterial (IA) administration of a thrombolytic agent (reteplase) in a primate model of intracranial thrombosis. We introduced thrombus through superselective catheterization of the intracranial segment of the internal carotid artery in 16 primates. The animals were randomly assigned to receive IA reteplase and IV abciximab ( n =4), IA reteplase and IV placebo ( n =4), IA placebo and IV abciximab ( n =4) or IA and IV placebo ( n =4). Recanalization was assessed by serial angiography during the 6-h period after initiation of treatment. Postmortem magnetic resonance (MR) imaging was performed to determine the presence of cerebral infarction or intracranial hemorrhage. Partial or complete recanalization at 6 h after initiation of treatment (decrease of two or more points in pre-treatment angiographic occlusion grade) was observed in two animals treated with IA reteplase and IV abciximab, three animals treated with IA reteplase alone and one animal treated with IV abciximab alone. No improvement in perfusion was observed in animals that received IV and IA placebo. Cerebral infarction was demonstrated on postmortem MR imaging in three animals that received IA and IV placebo and in one animal each from the groups that received IA reteplase and IV abciximab or IV abciximab alone. One animal that received IV abciximab alone had a small intracerebral hemorrhage on MR imaging. IA reteplase with or without abciximab appeared to be the most effective regimen for achieving recanalization in our model of intracranial thrombosis. Further studies are required in experimental models to determine the optimal dose, method of administration and efficacy of these medications in acute ischemic stroke.

BLOOD COAGULATION TESTS IN TOXICOLOGICAL STUDIES-REVIEW OF METHODS AND THEIR SIGNIFICANCE FOR DRUG SAFETY ASSESSMENT-

In general toxicological studies, prothrombin time and activated partial thromboplastin time are routinely measured to assess blood coagulation. Special (problem-driven) tests for blood coagulation are of significance to detect abnormalities and investigate the mechanism of toxicity in detail. In this review, we compiled widely scattered information on blood coagulation testing from different fields in the biological area, and reviewed the methods available and their significance in toxicological studies. The relevant literature cited here reports large species differences in platelet aggregation, coagulation factors or fibrinolysis, and technical limitations. However, the following tests are basically applicable to laboratory animals; (1) assays for individual coagulation factors and protein induced by vitamin K absence or antagonists (PIVKA) to investigate coagulation factor abnormalities; (2) platelet aggregation-, platelet adhesion-, platelet release-tests and von Willebrand factor assay to screen and/or investigate platelet dysfunction; (3) fibrin/fibrinogen degradation products (FDP), D-dimer and thromboelastogram to detect fibrinolitic abnormalities, and assays for plasminogen, plasmin and their activator/inhibitor to investigate fibrinolysis in detail; and (4) bleeding-time to grossly evaluate blood coagulation capability in vivo. An appropriate battery of these tests provides significant information for risk assessment of drugs.

Doxazosin, an alpha-1 antagonist, prevents further progression of the advanced atherosclerotic lesion in hypercholesterolemic hamsters

The aim of this study was to examine the effect of doxazosin (DOX) on the further progression and regression of the advanced atherosclerotic lesion in the hypercholesterolemic hamster. Thirty-six, male F(1)B Golden Syrian hamsters, 10 weeks of age, were divided into 3 groups of 12 and fed a nonpurified hypercholesterolemic diet (HCD) containing 10% coconut oil and 0.1% cholesterol (wt/wt) for 9 months (HCD 9). One group of hamsters was euthanized at 9 months and their aortas were collected, fixed, and stored until analysis. The remaining hamsters were either maintained on the HCD for an additional 6 months (HCD 15) or fed the HCD plus 20 mg/kg/d DOX for the 6 months. At the end of the study (15 months), the DOX-treated hamsters had significantly lower plasma total cholesterol (TC) (-68%), low-density lipoprotein-cholesterol (LDL-C) (-73%), and triglycerides (TG) (-74%) compared with the HCD 15. The lumenal narrowing and intimal thickening atherosclerotic lesions were significantly less in the DOX-treated hamsters compared with the HCD 15 (-66% and -70%, respectively). These data suggest that DOX treatment prevents further progression of the advanced atherosclerotic lesion possibly by lowering plasma TC, LDL-C, and TG in hypercholesterolemic hamsters.