Antiplatelet therapy in the prevention of ischemic vascular events: Literature review and evidence-based guidelines for drug selection

Background: New antiplatelet drugs are being developed and many clinical tr ials evaluating the benefits of antiplatelet drugs for the secondary preven tion of ischemic events in patients with atherosclerotic vascular disease h ave been performed. Hypothesis: An updated systematic review and evidence-based guidelines for the appropriate selection of antiplatelet drugs may be beneficial to physic ians and healthcare organizations attempting to create or update current cl inical practice guidelines or clinical pathways aimed at caring for these p atients. Methods: (1) A systematic review of the recent literature on the relative e fficacy and safety of aspirin, ticlopidine, and clopidogrel was undertaken; (2) an evidence-based, expert panel approach using a modified Delphi techn ique to create explicit guidelines for prescribing antiplatelet therapy was instituted; and (3) the recommendations of an expert panel were summarized . Results: Consensus guidelines were developed for the utilization of aspirin , ticlopidine, or clopidogrel for the prevention of ischemic events in pati ents with manifestations of atherosclerotic vascular disease (prior myocard ial infarction, prior ischemic stroke, or established peripheral arterial d isease) who are at increased risk for recurrent ischemic events. Based on e fficacy and safety, clopidogrel was recommended as the drug of choice for p atients with established peripheral arterial disease; aspirin or clopidogre l should be considered in patients with prior myocardial infarction (with c lopidogrel favored for patients who have had a recurrent event while on asp irin or in whom aspirin is contraindicated); aspirin or clopidogrel should be considered as first-line treatment in patients with prior ischemic (nonh emorrhagic) stroke-however, clopidogrel is the favored drug in patients in whom other antiplatelet drugs are either contraindicated or who have had re current events while on therapy. Conclusions: Myocardial infarction, ischemic stroke, and peripheral arteria l disease are all clinical manifestations of the same underlying disease pr ocess (atherosclerosis), with thrombus formation on the disrupted atheroscl erotic plaque (atherothrombosis) being a common precipitating factor of isc hemic events in patients suffering from these disorders. An evidence-based approach was used to develop a practice guideline, based on available publi shed evidence, for the appropriate utilization of antiplatelet agents (aspi rin, ticlopidine, or clopidogrel). These guidelines may be of use to multid isciplinary teams wishing to create or update clinical guidelines or clinic al pathways which address the care of patients with atherosclerotic vascula r disease. New antiplatelet agents such as clopidogrel may be more effectiv e and associated with lower risk of selected adverse effects (such as gastr ointestinal distress, gastrointestinal hemorrhage, and neutropenia) than th ose previously used to prevent thrombus formation in the setting of atheros clerotic arterial disease. Combination antiplatelet therapy is being evalua ted as an option for those patients who experience recurrent events on a si ngle antiplatelet agent.