ANTITHROMBOTIC AGENTS IN CEREBRAL-ISCHEMIA

The choice of antithrombotic agent in cerebral ischemia depends on the pathogenesis: thrombo sis, embolism, or hemorrhage, Antiplatelet agents are considered most beneficial in thrombotic stroke, anticoagulants are most effective in cardioembolic stroke; antithrombotic agents are generally contraindicated in hemorrhagic stroke, A meta-analysis of 18 trials documented a 23% reduction in stroke risk with antiplatelet agents; aspirin is typically the antiplatelet agent of choice for stroke prevention, There are no definitive data regarding the optimal aspirin dose for stroke prevention and this issue remains controversial. Ticlopidine is the most effective antiplatelet agent, but its adverse effect profile restricts its use, Anticoagulants are highly effective for preventing cardioembolic stroke, but their effectiveness in non-cardioembolic stroke is uncertain because of lack of trial data. Results of the ongoing Warfarin/Aspirin Recurrent Stroke Study (warfarin [INR 1.8-2.8] vs aspirin [325 mg/day]) may clarify this issue, There is renewed interest in thrombolytics because recent data indicate that reperfusion within a few hours of stroke onset appears to be effective in preventing in neuronal damage. In addition, when given within 6 hours of stroke onset, thrombolytics appear to be relatively safe, Several direct thrombin Inhibitors are being evaluated, Experimentally, hirudin, hirulog, D-Phe-L-Pro-L-Arg-CH2Cl (PPACK), and argatroban are clearly more effective than heparin In inhibiting platelet deposition and thrombus formation, and also show promise in preventing reocclusion after thrombolysis for both experimental thrombotic and embolic stroke, However, the risk of hemorrhage in patients with cerebrovascular disease is unknown for these agents. New antiplatelet agents, most of which inhibit the platelet IIb/IIIa receptor, have also shown a significant reduction in ischemic complications in experimental thrombosis models.