Thiol isomerases in thrombus formation

Protein disulfide isomerase (PDI), ERp5, and ERp57, among perhaps other thiol isomerases, are important for the initiation of thrombus formation. Using the laser injury thrombosis model in mice to induce in vivo arterial thrombus formation, it was shown that thrombus formation is associated with PDI secretion by platelets, that inhibition of PDI blocked platelet thrombus formation and fibrin generation, and that endothelial cell activation leads to PDI secretion. Similar results using this and other thrombosis models in mice have demonstrated the importance of ERp5 and ERp57 in the initiation of thrombus formation. The integrins, αIIbβ3 and αVβ3, play a key role in this process and interact directly with PDI, ERp5, and ERp57. The mechanism by which thiol isomerases participate in thrombus generation is being evaluated using trapping mutant forms to identify substrates of thiol isomerases that participate in the network pathways linking thiol isomerases, platelet receptor activation, and fibrin generation. PDI as an antithrombotic target is being explored using isoquercetin and quercetin 3-rutinoside, inhibitors of PDI identified by high throughput screening. Regulation of thiol isomerase expression, analysis of the storage, and secretion of thiol isomerases and determination of the electron transfer pathway are key issues to understanding this newly discovered mechanism of regulation of the initiation of thrombus formation.

Targeting glycoprotein VI and the immunoreceptor tyrosine-based activation motif signaling pathway

Coronary artery thrombosis and ischemic stroke are often initiated by the disruption of an atherosclerotic plaque and consequent intravascular platelet activation. Thus, antiplatelet drugs are central in the treatment and prevention of the initial, and subsequent, vascular events. However, novel pharmacological targets for platelet inhibition remain an important goal of cardiovascular research because of the negative effect of existing antiplatelet drugs on primary hemostasis. One promising target is the platelet collagen receptor glycoprotein VI. Blockade or antibody-mediated depletion of this receptor in circulating platelets is beneficial in experimental models of thrombosis and thrombo-inflammatory diseases, such as stroke, without impairing hemostasis. In this review, we summarize the importance of glycoprotein VI and (hem)immunoreceptor tyrosine-based activation motif signaling in hemostasis, thrombosis, and thrombo-inflammatory processes and discuss the targeting strategies currently under development for inhibiting glycoprotein VI and its signaling.

Perioperative management of antiplatelet therapy

Worldwide, cardiovascular events represent the major cause of morbidity and mortality. A key role in the pathogenesis of these events is played by platelets. Interventional procedures, with placement of coronary and vascular stents, often represent the preferred therapeutic strategy. Antiplatelet medications are considered first-line therapy in preventing cardiovascular thrombotic events. A wide array of antiplatelet agents is available, each with different pharmacological properties. When patients on antiplatelet agents present for surgery, the perioperative team must design an optimal strategy to manage antiplatelet medications. Each patient is stratified according to risk of developing a cardiovascular thrombotic event and inherent risk of surgical bleeding. After risk stratification analysis, various therapeutic pathways include continuing or discontinuing all antiplatelet agents or maintaining one antiplatelet agent and discontinuing the other. This review focuses on the pharmacological and pharmacokinetic properties of both older and novel antiplatelet drugs, and reviews current literature and guidelines addressing options for perioperative antiplatelet management.

Combined therapeutic effect of probucol and cilostazol on endothelial function in patients with silent cerebral lacunar infarcts and hypercholesterolemia: a preliminary study

OBJECTIVE

This study evaluated the efficacy of combined therapy with probucol and cilostazol on endothelial function in silent lacunar cerebral infarcts (SLCI) and mild hypercholesterolemia.

SUBJECTS AND METHODS

Flow-mediated vasodilatation (FMD) and nitroglycerin-induced vasodilatation (NMD) were measured before and after 4 weeks of combined therapy with probucol (500 mg/day) and cilostazol (200 mg/day) in 34 patients with a mean age of 72 ± 7 years (range 57-80 years) with SLCI, mild hypercholesterolemia (low-density lipoprotein cholesterol >100 mg/dl) and impaired endothelial function (FMD <6%). Patients were randomly allocated to one of the following two treatment groups: (1) aspirin (100 mg/day) with behavioral modifications, such as diet and/or exercise therapy (A group or control group, n = 17), and (2) probucol and cilostazol treatment (PC group, n = 17), also with behavioral modifications.

RESULTS

Although the baseline FMD was not different between the two treatment arms (2.7 ± 1.5 vs. 2.6 ± 1.5%, n.s.), the posttreatment FMD was significantly improved in the PC group (from 2.7 ± 1.5 to 3.5 ± 1.7%, p < 0.05) but not in the A group (from 2.6 ± 1.5 to 2.9 ± 1.4%, n.s.). No differences were observed between baseline and posttreatment NMD in either group. The effects of treatments on lipid profiles were more profound in the PC group.

CONCLUSION

Combined treatment with probucol and cilostazol resulted in subacute improvement in FMD/endothelial function in patients with SLCI with mild hypercholesterolemia. This combination therapy has the potential to reduce the risk of cardiovascular events via improvements in endothelial function and lipid profiles.

Impact of smoking on long-term outcomes in patients with atherosclerotic vascular disease treated with aspirin or clopidogrel: insights from the CAPRIE trial (Clopidogrel Versus Aspirin in Patients at Risk of Ischemic Events)

OBJECTIVES

The goal of this study was to investigate the differential efficacy of clopidogrel or aspirin monotherapy according to smoking status in patients with atherosclerotic vascular disease.

BACKGROUND

Smoking enhances clopidogrel-induced platelet inhibition, which may explain the higher relative benefit among smokers observed in trials evaluating dual antiplatelet therapy. Whether smoking has an impact on clinical outcomes in patients requiring a single antiplatelet agent remains unknown.

METHODS

This was a post-hoc analysis of the CAPRIE (Clopidogrel Versus Aspirin in Patients at Risk of Ischemic Events) trial that compared clopidogrel and aspirin monotherapy in patients (N = 19,184) with atherosclerotic vascular disease.

RESULTS

Current smokers (n = 5,688) had an increased risk of ischemic events compared with never smokers (n = 4,135; hazard ratio [HR]: 1.24 [95% confidence interval (CI): 1.08 to 1.42]) and ex-smokers (n = 9,381; HR: 1.32 [95% CI: 1.18 to 1.47]) (p < 0.001). Clopidogrel was associated with a reduction in ischemic events among current smokers (8.3% vs. 10.8%; HR: 0.76 [95% CI: 0.64 to 0.90]), whereas no benefit over aspirin was seen in the combined group of ex-smokers/never-smoked patients (10.4% vs. 10.6%; HR: 0.99 [95% CI: 0.89 to 1.10]; p = 0.01 for interaction). Among current smokers, clopidogrel also reduced myocardial infarction, vascular death, and death from any cause compared with aspirin. No interaction between smoking status and study treatment was observed for bleeding events.

CONCLUSIONS

In a post-hoc analysis of the CAPRIE population, current smokers appeared to have enhanced benefit with clopidogrel therapy for secondary prevention compared with aspirin. These results should be considered hypothesis generating for future prospective studies assessing the impact of specific platelet-inhibiting strategies according to smoking status.

Impact of CYP2C19 genetic testing on provider prescribing patterns for antiplatelet therapy after acute coronary syndromes and percutaneous coronary intervention

BACKGROUND

Patients treated with clopidogrel who have ≥1 loss of function alleles for CYP2C19 have an increased risk for adverse cardiovascular events. In 2010, the US Food and Drug Administration issued a boxed warning cautioning against the use of clopidogrel in such patients. We sought to assess the impact of CYP2C19 genetic testing on prescribing patterns for antiplatelet therapy among patients with acute coronary syndrome or percutaneous coronary intervention.

METHODS AND RESULTS

Patients with recent acute coronary syndrome or percutaneous coronary intervention prescribed clopidogrel were offered CYP2C19 testing. Genotype and phenotype results were provided to patients and their physicians, but no specific treatment recommendations were suggested. Patients were categorized based on their genotype (carriers versus noncarriers) and phenotype (extensive, intermediate, and poor metabolizers). The primary outcome was intensification in antiplatelet therapy defined as either dose escalation of clopidogrel or replacement of clopidogrel with prasugrel. Between July 2010 and April 2012, 6032 patients were identified, and 499 (8.3%) underwent CYP2C19 genotyping, of whom 146 (30%) were found to have ≥1 reduced function allele, including 15 (3%) with 2 reduced function alleles. Although reduced function allele carriers were significantly more likely than noncarriers to have an intensification of their antiplatelet therapy, only 20% of poor metabolizers of clopidogrel had their antiplatelet therapy intensified.

CONCLUSIONS

Providers were significantly more likely to intensify antiplatelet therapy in CYP2C19 allele carriers, but only 20% of poor metabolizers of clopidogrel had an escalation in the dose of clopidogrel or were switched to prasugrel. These prescribing patterns likely reflect the unclear impact and evolving evidence for clopidogrel pharmacogenomics.

Differentiating haemostasis from thrombosis for therapeutic benefit

The central role of platelets in the formation of the primary haemostatic plug as well as in the development of arterial thrombosis is well defined. In general, the molecular events underpinning these processes are broadly similar. Whilst it has long been known that disturbances in blood flow, changes in platelet reactivity and enhanced coagulation reactions facilitate pathological thrombus formation, the precise details underlying these events remain incompletely understood. Intravital microscopy studies have highlighted the dynamic and heterogeneous nature of thrombus development and demonstrated that there are considerable spatiotemporal differences in the activation states of platelets within a forming thrombus. In this review we will consider the factors regulating the activation state of platelets in a developing thrombus and discuss how specific prothrombotic factors may influence this process, leading to excessive thrombus propagation. We will also discuss some potentially novel therapeutic approaches that may reduce excess thrombus development whilst minimising bleeding risk.

Tumor vascular disrupting agent 5,6-dimethylxanthenone-4-acetic acid inhibits platelet activation and thrombosis via inhibition of thromboxane A2 signaling and phosphodiesterase

BACKGROUND

5,6-Dimethylxanthenone-4-acetic acid (DMXAA) is a tumor vascular disrupting agent under clinical trials as an adjacent antitumor agent. DMXAA is structurally similar to flavone-8-acetic acid (FAA), an old tumor vascular disrupting agent with antiplatelet and antithrombotic effects. In contrast to FAA, which causes bleeding in tumor patients, no bleeding has been reported in patients receiving DMXAA. Whether DMXAA also affects platelet function is not clear.

OBJECTIVES

To determine the effects of DMXAA on platelet function and explore the underlying mechanisms.

METHODS AND RESULTS

DMXAA concentration-dependently inhibited human platelet aggregation and ATP release induced by U46619, arachidonic acid, ADP, collagen, or ristocetin. Furthermore, DMXAA inhibited phosphorylation of Erk1/2 and Akt downstream of thromboxane A2 signaling inhibition. DMXAA also inhibited human platelet phosphodiesterase. The antiplatelet effects were further confirmed using mice administered DMXAA intravenously. DMXAA dramatically inhibited thrombus formation in FeCl3 -injured mouse mesenteric arterial thrombus model and laser-injured mouse cremaster arteriole thrombus model. Notably, at a dose exhibiting antithrombotic effects similar to those of clopidogrel in mice, DMXAA did not significantly increase bleeding.

CONCLUSIONS

For the first time, we found that tumor vascular disrupting agent DMXAA has potent antiplatelet and antithrombotic effects without any bleeding diathesis. As DMXAA inhibits platelet activity with safe profile, DMXAA could be used as an efficacious and safe antiplatelet drug.

Predictors of 1-year outcomes in the Taiwan Acute Coronary Syndrome Full Spectrum Registry

BACKGROUND/PURPOSE

Evidence-based guidelines have been formulated for optimal management of acute coronary syndrome (ACS). The Taiwan ACS Full Spectrum Registry aimed to evaluate the ACS management and identify the predictors of clinical outcomes of death/myocardial infarction/stroke 1 year post hospital discharge.

METHODS

Three thousand and eighty confirmed ACS patients enrolled in this registry were followed up for 1 year at 3-month intervals. Patient data on medical interventions as well as clinical events were recorded and analyzed by descriptive statistics.

RESULTS

One-year mortality among patients with ST-segment elevation myocardial infarction (STEMI), non-STEMI (NSTEMI) and unstable angina was 6.1%, 10.1%, and 6.2%, respectively. Use of secondary preventive therapies was suboptimal throughout the follow-up phase, especially dual antiplatelet therapy, which fell from 74.8% patients at discharge to 24.9% patients at 1-year follow-up. The odds of an adverse incidence of death/myocardial infarction/stroke 1 year after discharge was significantly reduced in patients receiving aspirin and clopidogrel for ≥9 months and was consequently higher in patients in whom dual antiplatelet therapy was discontinued or prescribed for <9 months. Chronic renal failure, in-hospital bleeding, a diagnosis of NSTEMI, and antiplatelet therapy discontinuation had a negative association with 1-year outcomes, whereas the use of drug-eluting stents and antiplatelet agents, clopidogrel and aspirin, were predictors of positive outcomes.

CONCLUSION

There is a significant deviation from evidence-based guidelines in ACS management in Taiwan as reported in other countries. Policy adherence, especially with regard to dual antiplatelet therapy may hold the key to long-term favorable outcomes and improved survival rates in ACS patients in Taiwan.

Risk of lower and upper gastrointestinal bleeding, transfusions, and hospitalizations with complex antithrombotic therapy in elderly patients

BACKGROUND

Complex antithrombotic therapy (CAT) prescribed to elderly patients increases the risk of gastrointestinal bleeding. We quantified upper (UGIE) and lower gastrointestinal (LGIE) events, transfusions, and hospitalizations in a national cohort of elderly veterans prescribed CAT.

METHODS AND RESULTS

Veterans ≥60 years of age prescribed anticoagulant-antiplatelet, aspirin (ASA)-antiplatelet, ASA-anticoagulant, or triple therapy (ie, TRIP, anticoagulant-antiplatelet-ASA) were identified from the national pharmacy database (October 1, 2002 to September 30, 2008). Prescription-fill data were linked to Veteran Affairs and Medicare encounter files, each person-day of follow-up was assessed for CAT exposure, and outcomes were defined by using diagnostic code algorithms derived following chart abstraction. Incidence density ratios (compared with the reference category of no CAT) and survival analysis was conducted. Among 78,133 veterans (98.6% white; mean age, 72.3 [standard deviation 7.7]), 64% were prescribed ASA-antiplatelet and anticoagulant-antiplatelet and 6% were prescribed TRIP. The incidence of UGIE was 20.1/1000 patient-years, and the incidence of LGIE was 70.1/1000 patient-years. ASA-anticoagulant and TRIP were associated with the highest incidence of transfusion and hospitalization. A 40% to 60% increased risk of UGIE was observed with all strategies. LGIE was 30% higher with anticoagulant-antiplatelet, and transfusion increased with ASA-anticoagulant (hazard ratio, 6.1; 95% confidence interval, 5.2-7.1) and TRIP (hazard ratio, 5.0; 95% confidence interval, 4.2-5.8). Increased risk of hospitalization was noted with all strategies. The number needed to harm for UGIE or LGIE ranged from 52 to 65 and 15 to 23, respectively. The number needed to harm for hospitalization was 39 (anticoagulant-antiplatelet), 34 (ASA-anticoagulant), 67 (ASA-antiplatelet), and 45 (TRIP) patients.

CONCLUSIONS

Among elderly patients, CAT-related LGIE and UGIE are clinically relevant risks resulting in increased hospitalizations and transfusions.

The role of oral vitamin K antagonists in the outcome of infrainguinal bypass procedures

We investigated the role of oral vitamin K antagonists (VKAs) in graft patency, limb salvage, major and minor bleeding rates in patients undergoing infrainguinal bypass surgery. Five randomized-controlled trials (RCTs; n = 3746 patients) comparing VKA versus non-VKA treatment outcomes in patients undergoing infrainguinal bypass surgery were analyzed. The VKA treatment was associated with improved graft patency rates when a vein graft was used (risk ratio [RR]: 0.74; P = .0004), while there was no difference with prosthetic grafts (RR: 1.07; P = .39). The VKA treatment was also associated with improved limb salvage rates (RR: 0.33; P = .0008). Major and minor bleeding complications were higher in the VKA group. In conclusion, VKA treatment is associated with improved graft patency and limb salvage rates when a vein graft is used at the price of an increased risk of bleeding. Due to the inconsistent results, further well-designed RCTs are needed.

Effects of endothelial dysfunction on residual platelet aggregability after dual antiplatelet therapy with aspirin and clopidogrel in patients with stable coronary artery disease

BACKGROUND

Dual antiplatelet therapy with aspirin and clopidogrel is widely used in patients with coronary stents. High residual platelet reactivity (high RPR) after dual antiplatelet therapy is associated with increased cardiovascular events. Endothelial function could affect platelet reactivity in vivo. We hypothesized that endothelial dysfunction could be associated with high RPR after dual antiplatelet therapy in patients with stable coronary artery disease.

METHODS AND RESULTS

We screened patients with stable coronary artery disease for cytochrome P450 (CYP) 2C19 genotypes and enrolled 103 patients who lacked CYP2C19*2 or *3 loss-of-function allele to minimize the effect of this gene on high RPR. All patients received aspirin (100 mg/d) and clopidogrel (75 mg/d for long-term treatment or a loading dose of 300 mg) before the following tests. Platelet aggregability was assessed as P2Y12 reaction unit using the VerifyNow System. High RPR was defined as P2Y12 reaction unit ≥ 230. Peripheral endothelial function was expressed as reactive hyperemia index using reactive hyperemia peripheral arterial tonometry. Fifty-three patients exhibited high RPR. High RPR patients were significantly older, had higher levels of B-type natriuretic peptide, and were predominantly hypertensive compared with non-high RPR patients. Reactive hyperemia index was significantly lower in high RPR patients (0.46 ± 0.15) compared with non-high RPR patients (0.61 ± 0.18; P<0.001). Linear regression analysis demonstrated significant negative correlation between reactive hyperemia index and P2Y12 reaction unit (r=-0.32; P=0.001). Multivariable logistic regression analysis identified reactive hyperemia index as an independent and significant determinant of high RPR (odds ratio, 0.55; 95% confidence interval, 0.39-0.78; P=0.001).

CONCLUSIONS

In patients with stable coronary artery disease, endothelial function was significantly impaired in high RPR patients. Endothelial dysfunction is independently correlated with high RPR after dual antiplatelet therapy.

CLINICAL TRIAL REGISTRATION URL

http://www.umin.ac.jp/ctr. Unique identifier: UMIN000008239.

Antiplatelet and antithrombin strategies in acute coronary syndrome: state-of-the-art review

Antiplatelet and antithrombotic agents significantly alter the clinical course of patients with acute coronary syndrome (ACS) and hence form the bedrock of the management pathway of this closely related continuum of coronary pathologies. The contemporary therapeutic armamentarium for the treatment of ACS now reflects the many technical and pharmacological advances that took place over the last two decades. In the original 1996 American College of Cardiology/ American Heart Association (ACC/AHA) guidelines for the management of acute myocardial infarction, only one antiplatelet agent (Aspirin) and one anticoagulant (unfractionated heparin) were recommended as class I therapies. Since then many newer agents have been developed and approved for routine clinical use in ACS patients. Recent research has focussed on improving efficacy on one hand and reducing bleeding complications on the other. This review focuses on the mechanism, efficacy, safety profile and clinical trial evidence of P2 Y12 receptor antagonist antiplatelet agents, glycoprotein IIb/IIIa receptor inhibitors (GPI), protease-activated receptor-1 (PAR-1) inhibitors, thrombin inhibitor bivalirudin and Factor Xa inhibitors fondaparinaux and rivaroxaban.

Prevention of the renarrowing of coronary arteries using drug-eluting stents in the perioperative period: an update

The management of patients scheduled for surgery with a coronary stent, and receiving 1 or more antiplatelet drugs, has many controversies. The premature discontinuation of antiplatelet drugs substantially increases the risk of stent thrombosis (ST), myocardial infarction, and cardiac death, and surgery under an altered platelet function could also lead to an increased risk of bleeding in the perioperative period. Because of the conflict in the recommendations, this article reviews the current antiplatelet protocols after positioning a coronary stent, the evidence of increased risk of ST associated with the withdrawal of antiplatelet drugs and increased bleeding risk associated with its maintenance, the different perioperative antiplatelet protocols when patients are scheduled for surgery or need an urgent operation, and the therapeutic options if excessive bleeding occurs.

Emerging antiplatelet agents, differential pharmacology, and clinical utility

The aspirin–clopidogrel combination is the current gold standard antiplatelet regimen following percutaneous coronary intervention and for the treatment of acute coronary syndrome. Despite the clinical benefit of this combination, patients continue to have vascular events. Another purinergic (P2Y₁₂) receptor antagonist, prasugrel, became available last year. Although prasugrel is superior to clopidogrel in reducing clinical endpoints, a higher bleeding rate has been identified particularly in high-risk patients. Ticagrelor, a reversible P2Y₁₂ receptor antagonist currently being evaluated for approval, is also more potent than clopidogrel but has a similar bleeding risk. Two additional P2Y₁₂ antagonists are being investigated that will be available as an intravenous formulation. Apart from the P2Y₁₂ receptor antagonists, multiple other agents are being developed with unique mechanisms of platelet inhibition. These agents are being studied as an alternative to or in combination with clopidogrel. The antiplatelet agents currently under development include: thrombin receptor antagonists, phosphodiesterase inhibitors, a thromboxane–prostaglandin receptor antagonist, a serotonin receptor blocker, a platelet adhesion antagonist, nitric oxide-releasing aspirin, a glycoprotein VI antagonist, and a cyclooxygenase inhibitor. The purpose of this review is to describe the efficacy and safety profiles of the emerging antiplatelet agents and their role in the treatment of atherosclerotic cardiovascular diseases.

Modern role for clopidogrel in management of atrial fibrillation and stroke reduction

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia. The prevalence of AF increases sharply in old age (prevalence approximately 10% among persons 80 years of age and older). The expected risk for ischemic stroke is increased five-fold by the presence of AF, primarily as a result of cardiogenic embolism. Multiple large-scale, randomized trials have been completed or are still underway to find optimal, efficacious, and relatively safe ways to reduce the risk of ischemic stroke and other systemic thromboembolic events related to AF. Antithrombotic strategies are accompanied by serious bleeding complications that threaten patients in need of medical stroke prevention. Treatment regimens for preventing thromboembolism in AF patients range from vitamin K antagonists such as warfarin or coumadins, antiplatelet drugs like aspirin or clopidogrel, to newly developed orally available antithrombotics like the direct thrombin inhibitor dabigatran, or the Factor Xa-inhibitor rivaroxaban. The available anticoagulant and antiplatelet drugs have different advantages and disadvantages. This review attempts to delineate the specific role of clopidogrel in patients with AF and at risk of stroke, taking into consideration new and ongoing trials in this important field of medical practice.

Use of clopidogrel in the reduction of myocardial damage during percutaneous coronary intervention

It is estimated that approximately a quarter of patients undergoing coronary intervention may have significant post-procedural creatinine (CK)/creatinine kinase myocardial band (CK-MB) elevations and approximately half may have post-procedural troponin elevations. Current data suggest that periprocedural infarction is associated with short-, intermediate-, and long-term adverse outcomes, most notably mortality. This review examines the role of clopidogrel in decreasing periprocedural myonecrosis following percutaneous coronary intervention (PCI). Clopidogrel is an important pharmacologic agent used to reduce myocardial infarction post-coronary intervention as assessed directly by the evaluation of cardiac biomarkers and indirectly by the evaluation of short-term ischemic events. The optimal dose of clopidogrel is considered to be at least 300 mg given 6 to 15 hours prior to PCI but there is considerable evidence to suggest that a loading dose of 600 mg given 2 to 6 hours prior to PCI may be more efficacious in limiting post-coronary intervention events. The benefit obtained from clopidogrel appears independent of and incremental to that of other antiplatelet and antithrombotic agents used during and after coronary intervention.

Clopidogrel-induced spontaneous spinal epidural hematoma

The hemorrhagic side effects associated with the use of clopidogrel are within the acceptable range and occur mainly at skin or gastrointestinal sites. We report a case of spontaneous spinal epidural hematoma (SSEH) in a 60-yr-old woman who was treated with clopidogrel for frequent transient ischemic attacks. To our knowledge, this is the second reported case of clopidogrel-induced SSEH. The patient's symptoms and past history of clopidogrel use suggested the diagnosis and made the procedure proceed quickly to operate SSEH 9 hr after the onset of paraplegia. The outcome was excellent. Therefore, with the popularity of antiplatelet prescription, physicians should keep in mind and urgently treat this unusual but critical side effect.

Value of antiplatelet therapy in preventing thrombotic events in generalized vascular disease

Atherothrombosis is the major underlying cause of acute coronary syndromes, ischemic stroke, and peripheral artery disease, and thus is the leading cause of death and disability in Western countries. Platelet inhibitors play a major role in preventing these ischemic complications. There is strong evidence from the Antiplatelet Trialists' Collaboration meta-analysis that aspirin reduces the combined risk of stroke, myocardial infarction (MI), or vascular death in atherosclerotic patients. The Ticlopidine Aspirin Stroke Study (TASS) compared aspirin and ticlopidine in the secondary prevention of high-risk patients after ischemic stroke and demonstrated a significant advantage for ticlopidine over aspirin. In peripheral arterial disease, the Swedish Ticlopidine Multicentre Study (STIMS) showed that ticlopidine was very effective against placebo. Intravenous antiplatelet agents, such as abciximab, tirofiban, and eptifibitide were also proven effective in acute coronary syndromes and unstable angina. In the Clopidogrel versus Aspirin in Patients at Risk of Ischaemic Events (CAPRIE) trial, clopidogrel was compared with aspirin in patients with symptomatic atherothrombosis regardless of the initial localization of the ischemic event (coronary, cerebral, or peripheral). The efficacy of clopidogrel based on the first occurrence of ischemic stroke, MI, or vascular death showed a relative risk reduction of 8.7% over and above the 25% reduction currently accepted with aspirin (p < 0.05). The greatest benefit of clopidogrel was in the reduction of fatal and nonfatal MI in the most severe groups of patients, providing a 19% relative risk reduction (p = 0.008). The recent disappointing results obtained with oral glycoprotein IIb/IIIa receptor blocking agents may emphasize the need for other antiplatelet combination therapy, such as aspirin-clopidogrel, in coronary disease, stents, stroke, and possibly atherothrombosis in high-risk patients.