Design of the blockade of the glycoprotein IIb/IIIa receptor to avoid vascular occlusion (BRAVO) trial

Eptifibatide, an Older Therapeutic Peptide with New Indications: From Clinical Pharmacology to Everyday Clinical Practice

Therapeutic peptides are oligomers or short polymers of amino acids used for various medical purposes. Peptide-based treatments have evolved considerably due to new technologies, stimulating new research interests. They have been shown to be beneficial in a variety of therapeutic applications, notably in the treatment of cardiovascular disorders such as acute coronary syndrome (ACS). ACS is characterized by coronary artery wall damage and consequent formation of an intraluminal thrombus obstructing one or more coronary arteries, leading to unstable angina, non-ST elevated myocardial infarction, and ST-elevated myocardial infarction. One of the promising peptide drugs in the treatment of these pathologies is eptifibatide, a synthetic heptapeptide derived from rattlesnake venom. Eptifibatide is a glycoprotein IIb/IIIa inhibitor that blocks different pathways in platelet activation and aggregation. In this narrative review, we summarized the current evidence on the mechanism of action, clinical pharmacology, and applications of eptifibatide in cardiology. Additionally, we illustrated its possible broader usage with new indications, including ischemic stroke, carotid stenting, intracranial aneurysm stenting, and septic shock. Further research is, however, required to fully evaluate the role of eptifibatide in these pathologies, independently and in comparison to other medications.

Oral antiplatelet therapy for acute ischaemic stroke

BACKGROUND

In people with acute ischaemic stroke, platelets become activated and can cause blood clots to form and block an artery in the brain, resulting in damage to part of the brain. Such damage gives rise to the symptoms of stroke. Antiplatelet therapy might reduce the volume of brain damaged by ischaemia and also reduce the risk of early recurrent ischaemic stroke, thereby reducing the risk of early death and improving long-term outcomes in survivors. However, antiplatelet therapy might also increase the risk of fatal or disabling intracranial haemorrhage.

OBJECTIVES

To assess the efficacy and safety of immediate oral antiplatelet therapy (that is started as soon as possible and no later than two weeks after stroke onset) in people with acute presumed ischaemic stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (last searched 16 October 2013), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 4, 2013), MEDLINE (June 1998 to May 2013), and EMBASE (June 1998 to May 2013). In 1998, for a previous version of this review, we searched the register of the Antiplatelet Trialists' Collaboration, MedStrategy and contacted relevant drug companies.

SELECTION CRITERIA

Randomised trials comparing oral antiplatelet therapy (started within 14 days of the stroke) with control in people with definite or presumed ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied the inclusion criteria and assessed trial quality. For the included trials, they extracted and cross-checked the data.

MAIN RESULTS

We included eight trials involving 41,483 participants. No new trials have been added since the last update.Two trials testing aspirin 160 mg to 300 mg once daily, started within 48 hours of onset, contributed 98% of the data. The risk of bias was low. The maximum follow-up was six months. With treatment, there was a significant decrease in death or dependency at the end of follow-up (odds ratio (OR) 0.95, 95% confidence interval (CI) 0.91 to 0.99). For every 1000 people treated with aspirin, 13 people would avoid death or dependency (number needed to treat 79). Antiplatelet therapy was associated with a small but definite excess of symptomatic intracranial haemorrhages, but this small hazard was significantly outnumbered by the benefit, the reduction in recurrent ischaemic stroke and pulmonary embolus.

AUTHORS' CONCLUSIONS

Antiplatelet therapy with aspirin 160 mg to 300 mg daily, given orally (or by nasogastric tube or per rectum in people who cannot swallow) and started within 48 hours of onset of presumed ischaemic stroke, reduced the risk of early recurrent ischaemic stroke without a major risk of early haemorrhagic complications; long-term outcomes were improved.

Development of glycoprotein IIb–IIIa antagonists: translation of pharmacodynamic effects into clinical benefit

This article will review the development of glycoprotein IIb-IIIa antagonists, with particular emphasis on the characteristics and pharmacodynamic studies of each agent that is available for clinical use. Abciximab is a Fab fragment of the 7E3 antibody that has high affinity and a slow rate of dissociation from glycoprotein IIb-IIIa. In contrast, the small molecules eptifibatide and tirofiban, have a much more rapid rate of dissociation, with an off time of 10 to 15 s. Accordingly, the circulating pool of abciximab is predominantly associated with platelets, whereas maintenance of a consistent concentration of tirofiban and eptifibatide in the blood is critical in order to achieve and sustain their inhibitory effects. The affinity of abciximab and tirofiban for glycoprotein IIb-IIIa are substantially greater than that of eptifibatide, necessitating maintenance of greater molar concentrations of eptifibatide in blood in order to achieve effective inhibition of the binding of fibrinogen to the activated conformer of glycoprotein IIb-IIIa.

Sex differences in stroke case fatality: a meta-analysis

BACKGROUND

In recent years, there were great controversies about gender disparities in stroke outcome. The study was aimed to investigate sex differences in stroke case fatality on all published studies based in a comprehensive meta-analysis.

METHODS

A systematic search of Pubmed, EMBASE, SCOPUS, ISI Web of Science, and Cochrane Library was conducted for the included papers between 1992 and 2009. For the pooled group and subgroup analysis, fixed effects or random effects model were used to find sex differences in case fatality of stroke with a Mantel-Haenszel method. Meta-regression analysis was performed to study methodological heterogeneity.

RESULTS

Thirty-six population-based studies, together with three randomized clinical trials (RCTs), were included in the present study. For the pooled group, there was an overall hazard risk of 1.13 for women compared with men. A hazard risk of 1.27 was observed for women in RCTs subgroup and 1.12 for women in population-based subgroup. The regression analysis found no significant correlation between methodological variables and heterogeneity.

CONCLUSIONS

Due to the limited data about sex differences in stroke case fatality, the findings should be treated cautiously as preliminary. More large multicenter clinical trials should be performed to verify the reliability of the results.

Anti-platelet therapy: glycoprotein IIb-IIIa antagonists

Glycoprotein (GP) IIb-IIIa antagonists inhibit the aggregation of activated platelets. Three agents are approved for clinical use. In this review, the characteristics of each agent, their pharmacodynamic profile, results in pivotal clinical trials and the associated clinical implications are discussed. GP IIb-IIIa antagonists have greatest benefit when used as adjunctive therapy during percutaneous coronary intervention (PCI) when the patient has intra-coronary thrombosis. These agents appear to provide greatest benefit when used in combination with heparin. The clinical niche for parenteral GP IIb-IIIa antagonists is evolving. The rapid onset and offset of GP IIb-IIIa antagonists plus dosing designed to inhibit extensively platelet aggregation differentiates them from oral agents. The contemporary niche appears to include patients in transition, such as individuals requiring emergent PCI before oral agents are fully active and for unstable patients requiring transport to PCI centres, particularly in patients likely to have intracoronary thrombus. Subsequent studies should evaluate the optimal duration of therapy with GP IIb-IIIa antagonists.

Antiplatelet agents for intermittent claudication

BACKGROUND

Peripheral arterial disease (PAD) is common and is a marker of systemic atherosclerosis. Patients with symptoms of intermittent claudication (IC) are at increased risk of cardiovascular events (myocardial infarction (MI) and stroke) and of both cardiovascular and all cause mortality.

OBJECTIVES

To determine the effectiveness of antiplatelet agents in reducing mortality (all cause and cardiovascular) and cardiovascular events in patients with intermittent claudication.

SEARCH METHODS

The Cochrane Peripheral Vascular Diseases group searched their Specialised Register (last searched April 2011) and CENTRAL (2011, Issue 2) for publications on antiplatelet agents and IC. In addition reference lists of relevant articles were also searched.

SELECTION CRITERIA

Double-blind randomised controlled trials comparing oral antiplatelet agents versus placebo, or versus other antiplatelet agents in patients with stable intermittent claudication were included. Patients with asymptomatic PAD (stage I Fontaine), stage III and IV Fontaine PAD, and those undergoing or awaiting endovascular or surgical intervention were excluded.

DATA COLLECTION AND ANALYSIS

Data on methodological quality, participants, interventions and outcomes including all cause mortality, cardiovascular mortality, cardiovascular events, adverse events, pain free walking distance, need for revascularisation, limb amputation and ankle brachial pressure indices were collected. For each outcome, the pooled risk ratio (RR) or mean difference (MD) with 95% confidence intervals (CI) was calculated.

MAIN RESULTS

A total of 12 studies with a combined total of 12,168 patients were included in this review. Antiplatelet agents reduced all cause (RR 0.76, 95% CI 0.60 to 0.98) and cardiovascular mortality (RR 0.54, 95% CI 0.32 to 0.93) in patients with IC compared with placebo. A reduction in total cardiovascular events was not statistically significant (RR 0.80, 95% CI 0.63 to 1.01). Data from two trials (which tested clopidogrel and picotamide respectively against aspirin) showed a significantly lower risk of all cause mortality (RR 0.73, 95% CI 0.58 to 0.93) and cardiovascular events (RR 0.81, 95% CI 0.67 to 0.98) with antiplatelets other than aspirin compared with aspirin. Antiplatelet therapy was associated with a higher risk of adverse events, including gastrointestinal symptoms (dyspepsia) (RR 2.11, 95% CI 1.23 to 3.61) and adverse events leading to cessation of therapy (RR 2.05, 95% CI 1.53 to 2.75) compared with placebo; data on major bleeding (RR 1.73, 95% CI 0.51, 5.83) and on adverse events in trials of aspirin versus alternative antiplatelet were limited. Risk of limb deterioration leading to revascularisation was significantly reduced by antiplatelet treatment compared with placebo (RR 0.65, 95% CI 0.43 to 0.97).

AUTHORS' CONCLUSIONS

Antiplatelet agents have a beneficial effect in reducing all cause mortality and fatal cardiovascular events in patients with IC. Treatment with antiplatelet agents in this patient group however is associated with an increase in adverse effects, including GI symptoms, and healthcare professionals and patients need to be aware of the potential harm as well as the benefit of therapy; more data are required on the effect of antiplatelets on major bleeding. Evidence on the effectiveness of aspirin versus either placebo or an alternative antiplatelet agent is lacking. Evidence for thienopyridine antiplatelet agents was particularly compelling and there is an urgent need for multicentre trials to compare the effects of aspirin against thienopyridines.

Is there an association between low dose aspirin and anemia (without overt bleeding)? Narrative review

Background

Overt bleeding associated with low dose aspirin (LDA) is well-recognized, little attention is given to the possibility of association between LDA and occult bleeding, although this is known to occur in healthy volunteers. LDA is used increasingly in primary and secondary prevention of a number of medical conditions, many of which are common in older people, as is anemia. Anemia in older people is associated with adverse outcomes including disability, morbidity and mortality. The purpose of this study was to review the evidence that LDA might cause anemia without overt bleeding.

Methods

An extensive narrative review was carried out. Electronic searching (including database links) and reference lists of reports were used to identify studies reporting on use of aspirin ≤325 mg/day and anemia or change in hemoglobin (Hb) without overt bleeding. Data were extracted from reports of trials, adverse drug reactions (ADRs) and prevalence studies of adults aged ≥18 years, published since 1980.

Results

There are few relevant data, with considerable heterogeneity among trial designs, duration, and patient characteristics in studies of LDA. In five randomised trials (n = 5879) in (mostly secondary) prevention, the majority of patients were men without peptic ulcer disease aged 50-70 years and no consistent association between LDA and change in Hb was found. In two smaller studies (n = 609) of primary prevention in healthy patients aged ≥70 years, there was a small but statistically significant fall in Hb with LDA. Observational studies, and data from trials in which use of LDA was not a primary focus of the study, were inconclusive.

Conclusions

It is not clear whether there is an association between LDA and anemia in the absence of overt bleeding, but there may be an association between LDA and fall in Hb in (a subset of) older patients. The available evidence has significant limitations, which are discussed; studies including more older patients, and publication of individual patient data, would help clarify this important matter.

Patients Enrolled in Large Randomized Clinical Trials of Antiplatelet Treatment for Prevention After Transient Ischemic Attack or Ischemic Stroke Are Not Representative of Patients in Clinical Practice

Background and Purpose— Many randomized clinical trials have evaluated the benefit of long-term use of antiplatelet drugs in reducing the risk of new vascular events in patients with a recent transient ischemic attack or ischemic stroke. Evidence from these trials forms the basis for national and international guidelines for the management of nearly all such patients in clinical practice. However, abundant and strict enrollment criteria may limit the validity and the applicability of results of randomized clinical trials to clinical practice. We estimated the eligibility for participation in landmark trials of antiplatelet drugs of an unselected group of patients with stroke or transient ischemic attack from a national stroke survey.

Methods— Nine hundred seventy-two patients with transient ischemic attack or ischemic stroke were prospectively and consecutively enrolled in the Netherlands Stroke Survey. We applied 7 large antiplatelet trials’ enrollment criteria.

Results— In total, 886 patients were discharged alive and available for secondary prevention. Mean follow-up was 2.5 years. The annual rate of transient ischemic attack, stroke, or nonfatal myocardial infarction was 6.7%. The proportions of patients fulfilling the trial enrollment criteria ranged from 25% to 67%. Mortality was significantly higher in ineligible patients (27% to 41%) than in patients fulfilling enrollment criteria (16% to 20%). Rates of vascular events were not higher in trial-eligible patients than in ineligible patients.

Conclusions— Our data confirm that patients with ischemic attack and stroke enrolled in randomized clinical trials are only partially representative of patients in clinical practice. Use of less strict enrollment criteria could enhance “generalizability” and result in more efficient selection of patients for randomized clinical trials.

Use of antiplatelet agents for prevention of ischemic stroke

Overall management to lower risk for ischemic stroke is multifaceted. Management includes measures to treat risk factors for accelerated atherosclerosis and stroke, antithrombotic therapies to lower the risk for thromboembolism, and surgery to treat a defined arterial or cardiac lesion. Treatment decisions are made on a case-by-case basis, with most patients receiving some combination of medication and recommendations for lifestyle modification. Some patients will also undergo surgical or endovascular interventions. This article discusses antithrombotic treatment for ischemic stroke prevention, placing major emphasis on the indications for and administration of antiplatelet therapy.

Relation between aspirin dose, all-cause mortality, and bleeding in patients with recent cerebrovascular or coronary ischemic events (from the BRAVO Trial)

Despite aspirin's established role in the treatment of atherosclerotic vascular disease, considerable controversy exists regarding its most effective dosing strategy. In a retrospective observational study, we examined the relation between prescribed aspirin dose (<162 mg vs > or =162 mg/day aspirin) and clinical outcome in 4,589 placebo-treated patients enrolled in the Blockage of the Glycoprotein IIb/IIIa Receptor to Avoid Vascular Occlusion (BRAVO) trial over a median follow-up of 366 days. Standard Cox regression analysis was employed because propensity analysis was not feasible. Compared with lower aspirin doses, higher doses were associated with lower unadjusted all-cause mortality (2.9 vs 1.6%, respectively; log rank chi-square 8.6, p = 0.0034). Higher aspirin dose remained independently predictive of lower all-cause mortality in a multivariable Cox proportional hazards model (hazard ratio 0.64, 95% confidence interval 0.42 to 0.97, p = 0.037). However, there was no significant difference in the incidence of the composite endpoint death, nonfatal myocardial infarction, or nonfatal stroke (6.1% vs 6.2%, p = 0.74). Higher aspirin dose was a significant independent predictor of any (hazard ratio 1.32, 95% confidence interval 1.12 to 1.55, p = 0.001) but not serious bleeding. In conclusion, our findings suggest that aspirin doses of > or =162 mg/day may be more beneficial than those <162 mg/day at preventing death.

Antiplatelet therapy for acute ischaemic stroke

BACKGROUND

In patients with acute ischaemic stroke, platelets become activated. Antiplatelet therapy might reduce the volume of brain damaged by ischaemia and reduce the risk of early recurrent ischaemic stroke. This might reduce the risk of early death and improve long-term outcome in survivors. However, antiplatelet therapy might also increase the risk of fatal or disabling intracranial haemorrhage.

OBJECTIVES

To assess the efficacy and safety of antiplatelet therapy in acute ischaemic stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched June 2007), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 2, 2007), MEDLINE (June 1998 to May 2007), and EMBASE (June 1998 to May 2007). In 1998, for a previous version of this review, we searched the register of the Antiplatelet Trialists' Collaboration, MedStrategy and contacted relevant drug companies.

SELECTION CRITERIA

Randomised trials comparing antiplatelet therapy (started within 14 days of the stroke) with control in patients with definite or presumed ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied the inclusion criteria and assessed trial quality, and for the included trials, extracted and cross-checked the data.

MAIN RESULTS

Twelve trials involving 43,041 participants were included. Two trials testing aspirin 160 mg to 300 mg once daily started within 48 hours of onset contributed 94% of the data. The maximum follow up was six months. With treatment, there was a significant decrease in death or dependency at the end of follow up (odds ratio 0.95, 95% confidence interval 0.91 to 0.99). For every 1000 patients treated with aspirin, 13 patients will avoid death or dependency (number needed to treat to benefit: 79). Antiplatelet therapy was associated with a small but definite excess of symptomatic intracranial haemorrhages, but this was more than offset by the reduction of recurrent ischaemic strokes and pulmonary embolus.

AUTHORS' CONCLUSIONS

Antiplatelet therapy with aspirin 160 mg to 300 mg daily, given orally (or by nasogastric tube or per rectum in patients who cannot swallow), and started within 48 hours of onset of presumed ischaemic stroke reduces the risk of early recurrent ischaemic stroke without a major risk of early haemorrhagic complications and improves long-term outcome.

Risk for cardiovascular outcomes among subjects with atherosclerotic cardiovascular disease and greater-than-normal estimated glomerular filtration rate

BACKGROUND AND OBJECTIVES

Estimating equations for calculating glomerular filtration rate (eGFR) occasionally identify patients with elevated eGFR, yet the prognostic significance remains to be determined. This study sought to define the association of an elevated eGFR on the risk for death and cardiovascular outcomes among subjects with atherosclerotic cardiovascular disease.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Data from 8941 subjects who had a history of atherosclerotic vascular disease and were enrolled in the Blockade of the Glycoprotein IIb/IIIa Receptor to Avoid Vascular Occlusion trial were analyzed. Time to the composite end point of death, congestive heart failure, myocardial infarction, or stroke was modeled using Cox proportion hazards regression. Glomerular filtration rate was estimated using the Modification of Diet in Renal Disease and Cockcroft-Gault formulas.

RESULTS

Compared with subjects with eGFR of 100 to 125 ml/min per 1.73 m2, subjects with eGFR > or = 125 (n = 462) were younger, female, and nonwhite. In addition, subjects with an elevated eGFR were more likely to have diabetes and congestive heart failure. In adjusted analyses, every 10-ml/min per 1.73 m2 decrease in eGFR < 100 was associated with a 13% increased hazard for the composite end point. In addition, every 10-ml/min per 1.73 m2 increase in eGFR > or = 100 was associated with a 9% increased hazard for the composite end point.

CONCLUSIONS

In individuals with a history of vascular disease, the relationship between eGFR and cardiovascular outcomes may be parabolic, with increased risk among patients with both reduced and elevated eGFR.

Current developments in anti-platelet therapy

Platelets play a life-saving role in hemostasis and blood clotting at sites of vascular injury and consequently are similarly involved in the pathological counterpart, namely thrombosis. Thus, anti-platelet therapy has become a mainstay in treatment and/or prophylaxis of conditions like myocardial infarction, stroke and other cardiovascular diseases. Acetyl-salicylic acid (ASA, aspirin) is still the most widely used agent and considered as the prototype antiplatelet drug. Since platelet activation occurs via several pathways that are not influenced by ASA, several other compounds have been developed to add to its beneficial effect. Currently four main classes of antiplatelet agents are available for clinical use: acetyl-salicylic acid (ASA), phosphodiesterase (PDE) inhibitors, thienopyridines and the intravenous GPIIb/IIIa antagonists. This article gives a concise review of these four classes of anti-platelet agents, using ASA as the reference standard.

Tirofiban for the treatment of ischaemic stroke

Tirofiban is one of three glycoprotein IIb/IIIa receptor antagonists approved by the US FDA, beside abciximab and eptifibatide. The approval of tirofiban covers conservative treatment of myocardial infarction and unstable angina, as well as percutaneous coronary intervention, for which treatment with tirofiban is recommended in moderate-to-high-risk patients. The efficacy of glycoprotein IIb/IIIa antagonists in myocardial infarction indicated that these agents may also be helpful in the treatment of acute ischaemic stroke. Although experimental data are lacking, observational studies are promising. In recent years, increasing effort in studying glycoprotein IIb/IIIa antagonists has been made, mostly for treatment with abciximab. However, there is one Phase II trial that investigated treatment with tirofiban.

Preventable stroke and stroke prevention

Stroke is a major cause of death and disability in the world. The main causes of stroke are atherothromboembolism and cardiogenic embolism. The main causal and treatable risk factors for atherothromboembolic ischemic stroke are increasing blood pressure (BP), increasing cholesterol, cigarette smoking and diabetes; and the main risk factors for cardiogenic ischemic stroke are atrial fibrillation (AF) and ischemic heart disease. Strategies to reduce the incidence of stroke include prevention of first-ever and recurrent stroke, and treatment of patients with acute stroke to reduce death and disability. The two main strategies of stroke prevention are the 'population' (or 'mass') approach and the 'high risk' approach. The 'population' approach aims to reduce stroke by lowering the prevalence and mean level of causal risk factors in the community, by means of public education and government legislation. The 'high risk' approach aims to reduce stroke by identifying individuals at high risk of stroke, and lowering their risk by means of optimal medical therapies. Level 1 evidence from randomized controlled trials indicates that effective treatments for high risk patients include control of causal risk factors (lowering BP, lowering blood cholesterol), antithrombotic therapy (antiplatelet therapy with aspirin, clopidogrel, or the combination of aspirin and dipyridamole for patients in sinus rhythm, and anticoagulation with warfarin or ximelagatran for patients in AF) and, where appropriate, carotid revascularization for patients with severe carotid stenosis.

Randomized, double-blind, placebo-controlled, international trial of the oral IIb/IIIa antagonist lotrafiban in coronary and cerebrovascular disease

BACKGROUND

This is the primary report of the large-scale evaluation of lotrafiban, an orally administered IIb/IIIa receptor antagonist, a unique trial with respect to the platelet antagonist, protocol design, and inclusion of cerebrovascular disease in a significant proportion of patients.

METHODS AND RESULTS

Patients with vascular disease were randomized to lotrafiban 30 or 50 mg BID on the basis of age and predicted creatinine clearance or placebo in addition to aspirin at a dose ranging from 75 to 325 mg/d at the discretion of the physician-investigator. Follow-up was for up to 2 years. The primary end point was the composite of all-cause mortality, myocardial infarction, stroke, recurrent ischemia requiring hospitalization, and urgent revascularization. Of 9190 patients enrolled from 23 countries and 690 hospitals, 41% had cerebrovascular disease at the time of entry, and 59% had coronary artery disease. Death occurred in 2.3% of placebo-assigned patients and 3.0% of lotrafiban-group patients (hazard ratio 1.33, 95% CI 1.03 to 1.72, P=0.026), and the cause of excess death was vascular related. There was no significant difference in the primary end point (17.5% compared with 16.4%, respectively; hazard ratio 0.94, 95% CI 0.85 to 1.03, P=0.19). Serious bleeding was more frequent in the lotrafiban group (8.0% compared with 2.8%; P<0.001). Serious bleeding was more common among patients who received higher doses of aspirin (>162 mg/d), with or without lotrafiban.

CONCLUSIONS

Lotrafiban, an orally administered platelet glycoprotein IIb/IIIa blocker, induced a 33% increase in death rate, which was vascular in origin and not affected by the type of atherosclerotic involvement at entry to the trial. Although the dose of aspirin was not randomly assigned, the finding of increased bleeding with doses >162 mg/d is noteworthy.

What is the role for improved long-term antiplatelet therapy after percutaneous coronary intervention?

BACKGROUND

Coronary stent placement has replaced balloon angioplasty as the percutaneous coronary intervention (PCI) method of choice, primarily because of its lower restenosis rate. Compared with aspirin (ASA) monotherapy or ASA plus warfarin, the ticlopidine and ASA combination is superior in reducing thrombotic events after stenting. Clopidogrel plus ASA appears to be at least as effective as ticlopidine and ASA. Intravenous glycoprotein IIb/IIIa inhibitors effectively prevent periprocedural thrombotic complications, but their short duration of action and parenteral dosing don't allow for long-term protection. This review aimed to answer how long after PCI with a stent patients are at risk for recurrent thrombotic events and what the optimal way to prevent them is.

RESULTS

Classically, ASA has been prescribed indefinitely, whereas adenosine diphosphate receptor antagonists have been discontinued after 2 to 4 weeks. However, the Clopidogrel in Unstable Angina to Prevent Recurrent Events (CURE) trial found that long-term dual antiplatelet therapy with clopidogrel and ASA was more effective than ASA alone in preventing major cardiovascular events in patients with acute coronary syndrome, including those treated with PCI.

CONCLUSION

Results from additional ongoing studies are needed to clarify the role of long-term dual oral antiplatelet therapy in preventing ischemic events in patients who have undergone PCI.

Short- and long-term oral antiplatelet therapy in acute coronary syndromes and percutaneous coronary intervention

Platelets play a central role in both the short- and long-term manifestations of atherothrombosis. In acute coronary syndrome (ACS), there is a steep rise in cardiovascular events early, followed by an incremental rise in cardiovascular events over the long term. This long-term event rate is related to persistent platelet activation and thrombin generation. There is therefore a need to optimize both short- and long-term oral antiplatelet and antithrombotic strategies. The benefits of aspirin therapy, when administered early and continued over the long term, were demonstrated in several early randomized trials. The Antithrombotic Trialists' Collaboration found a 46% reduction in vascular events with antiplatelet therapy (mostly aspirin). However, despite treatment with aspirin and proven therapies, recurrent events remain high. The adenosine diphosphate receptor antagonists, ticlopidine and clopidogrel, inhibit the early steps of platelet activation, degranulation, and release of prothrombotic and inflammatory mediators, while also preventing activation of the glycoprotein IIb/IIIa receptor. The Clopidogrel in Unstable angina to prevent Recurrent Events (CURE) trial demonstrated the benefits of aspirin plus clopidogrel in reducing major cardiovascular events (cardiovascular death, myocardial infarction [MI], and stroke reduced by 20%, p = 0.00009) in a broad range of patients with ACS when administered early and continued over the long term. The benefits emerge very rapidly after a 300 mg loading dose. For the large number of patients undergoing percutaneous coronary intervention in the CURE trial, there was a substantial risk reduction with clopidogrel pretreatment followed by long-term therapy (p < 0.002). This benefit was present, regardless of whether intervention was performed early or late. The significant benefits of aspirin and clopidogrel persist for the combined efficacy-safety end point of cardiovascular death, MI, stroke, or life-threatening bleeding when clopidogrel is started early, combined with aspirin and other standard therapies, and continued for up to one year.

Antiplatelet therapy for acute ischaemic stroke

BACKGROUND

In patients with acute ischaemic stroke, platelets become activated. Antiplatelet therapy might reduce the volume of brain damaged by ischaemia and reduce the risk of early recurrent ischaemic stroke. This might reduce the risk of early death and improve long-term outcome in survivors. However, antiplatelet therapy might also increase the risk of fatal or disabling intracranial haemorrhage.

OBJECTIVES

The aim of this review is to assess the efficacy and safety of antiplatelet therapy in acute ischaemic stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched August 2002), the Cochrane Controlled Trials Register (CCTR) (Cochrane Library Issue 1 2002), MEDLINE (June 1998-October 2001), and EMBASE (June 1998-February 2002). In 1998, for previous versions of this review, we searched the register of the Antiplatelet Trialists Collaboration, MedStrategy and contacted relevant drug companies.

SELECTION CRITERIA

Randomised trials comparing antiplatelet therapy (started within 14 days of the stroke) with control in patients with definite or presumed ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two reviewers independently applied the inclusion criteria and assessed trial quality, and for the included trials, extracted and cross-checked the data.

MAIN RESULTS

Nine trials involving 41,399 patients were included. Two trials testing aspirin 160 to 300 mg once daily started within 48 hours of onset contributed 98% of the data. The maximum follow-up was six months. With treatment, there was a significant decrease in death or dependency at the end of follow-up (OR = 0.94; 95% CI 0.91 to 0.98). In absolute terms, 13 more patients were alive and independent at the end of follow-up for every 1000 patients treated. Furthermore, treatment increased the odds of making a complete recovery from the stroke (OR = 1.06; 95% CI 1.01 to 1.11). In absolute terms, 10 more patients made a complete recovery for every 1000 patients treated. Antiplatelet therapy was associated with a small but definite excess of 2 symptomatic intracranial haemorrhages for every 1000 patients treated, but this was more than offset by a reduction of 7 recurrent ischaemic strokes and about one pulmonary embolus for every 1000 patients treated.

REVIEWER'S CONCLUSIONS

Antiplatelet therapy with aspirin 160 to 300 mg daily, given orally (or per rectum in patients who cannot swallow), and started within 48 hours of onset of presumed ischaemic stroke reduces the risk of early recurrent ischaemic stroke without a major risk of early haemorrhagic complications and improves long-term outcome.

Therapeutic potential of platelet glycoprotein IIb/IIIa receptor antagonists in the management of ischemic stroke

The only drug approved by the US FDA for use in patients with acute ischemic stroke is the thrombolytic, alteplase. Whereas alteplase rapidly restores blood flow, the drug has to be administered within 6 hours after symptom onset and is associated with an increased incidence of intracerebral hemorrhage (ICH). Moreover, transient and permanent re-occlusions associated with increased mortality continue to occur after thrombolysis with alteplase. Platelets are believed to play a pivotal role in the pathogenesis of atherothrombosis and the binding of the platelet glycoprotein (GP) IIb/IIIa receptor to fibrinogen is the final common pathway leading to platelet aggregation and thrombus formation. Antiplatelet agents such as platelet GP IIb/IIIa receptor antagonists have been studied in numerous multicenter, randomized clinical trials in patients with acute coronary symptoms (ACS). The intravenous GP IIb/IIIa receptor antagonists abciximab, eptifibatide and tirofiban are approved by the FDA for use in patients with ACS, and intravenous tirofiban is also approved for use during coronary intervention. Oral GP IIb/IIIa receptor antagonists such as lotrafiban, xemilofiban, sibrafiban and orbofiban have failed to provide myocardial protection in patients with ACS. Compared with ACS, few trials have evaluated the efficacy and tolerability of platelet GP IIb/IIIa receptor antagonists in patients with cerebrovascular syndromes. Agents such as SM-20302, TP201, ME3277, murine 7E3 F(ab')(2 )and SDZ-GPI 562 have been reported to preserve microvascular patency in different animal models of acute ischemic stroke and they may have neuroprotective properties. Platelet GP IIb/IIIa receptor antagonists may be suitable as a single therapeutic or as an adjunct therapeutic to thrombolysis with alteplase for the treatment of stroke. Platelet GP IIb/IIIa receptor antagonists may enhance the efficacy of thrombolytics and reduce potentially fatal adverse effects such as ICH. Preliminary results from the Abciximab in Emergent Stroke Treatment Trial (AbESTT) indicate that abciximab, administered as a bolus dose 0.25 mg/kg followed by 12-hour infusion, was associated with significant improvement in clinical rating scores and no significant increase in bleeding episodes in patients with acute stroke. The tolerability of argatroban in patients with acute stroke is currently being assessed in the multicenter Argatroban in Ischemic Stroke (ARGIS-1) trial.

Glicoprotein (GP) IIb/IIIa inhibitors for acute stroke treatment

The benefit of antiplatelet therapy remains unclear, although it does appear that aspirin monotherapy started within 48 hours of stroke onset may result in a modest clinical improvement. Glicoprotein (GP) IIb/IIIa antagonists are currently considered the most powerful specific inhibitors of platelet activation in acute thrombosis. Glicoprotein IIb/IIIa inhibitor therapy could merit a prominent role also in the initial management of patients with acute ischemic stroke. Abciximab may be promising in this setting and should be evaluated in further clinical trials.

Antithrombotic Secondary Prevention After Stroke

In patients with transient ischemic attack (TIA) or ischemic stroke of noncardiac origin, antiplatelet drugs are able to decrease the risk of stroke by 11% to 15%, and decrease the risk of stroke, myocardial infarction (MI), and vascular death by 15% to 22%. Aspirin leads to a moderate but significant reduction of stroke, MI, and vascular death in patients with TIA and ischemic stroke. Low doses are as effective as high doses, but are better tolerated in terms of gastrointestinal side effects. The recommended aspirin dose, therefore, is between 50 and 325 mg. Bleeding complications are not dose-dependent, and also occur with the lowest doses. The combination of aspirin (25 mg twice daily) with slow-release dipyridamole (200 mg twice daily) is superior compared with aspirin alone for stroke prevention. Ticlopidine is effective in secondary stroke prevention in patients with TIA and stroke. For some end points, it is superior to aspirin. Due to its side-effect profile (neutropenia, thrombotic thrombocytopenic purpura ), ticlopidine should be given to patients who are intolerant of aspirin. Prospective trials have not indicated whether ticlopidine is suggested for patients who have recurrent cerebrovascular events while on aspirin. Clopidogrel has a better safety profile than ticlopidine. Although not investigated in patients with TIA, clopidogrel should also be effective in these patients assuming the same pathophysiology than in patients with stroke. Clopidogrel is second-line treatment in patients intolerant for aspirin, and first-line treatment for patients with stroke and peripheral arterial disease or MI. A frequent clinical problem is patients who are already on aspirin because of coronary heart disease or a prior cerebral ischemic event, and then suffer a first or recurrent TIA or stroke. No single clinical trial has investigated this problem. Therefore, recommendations are not evidence-based. Possible strategies include the following: continue aspirin, add dipyridamole, add clopidogrel, switch to ticlopidine or clopidogrel, or switch to anticoagulation with an International Normalized Ratio (INR) of 2.0 to 3.0. The combination of low-dose warfarin and aspirin was never studied in the secondary prevention of stroke. In patients with a cardiac source of embolism, anticoagulation is recommended with an INR of 2.0 to 3.0. At the present time, anticoagulation with an INR between 3.0 and 4.5 cannot be recommended for patients with noncardiac TIA or stroke. Anticoagulation with an INR between 3.0 and 4.5 carries a high bleeding risk. Whether anticoagulation with lower INR is safe and effective is not yet known. Treatment of vascular risk factors should also be performed in secondary stroke prevention.

Inhibition of ADP-triggered blood platelet aggregation by diadenosine polyphosphate analogues

The synthesis and biological evaluation of new diadenosine polyphosphate analogues on blood platelet aggregation are reported. The most active are compounds with a sulfur atom replacing one or both non-bridging oxygens at phosphorus bound to adenosyl residues and hydroxymethyl groups of bis(hydroxymethyl)phosphinic acid.

The failure of orally administered glycoprotein IIb/IIIa inhibitors to prevent recurrent cardiac events

PURPOSE

Despite the success of intravenous glycoprotein IIb/IIIa antagonists, oral formulations have failed to show benefit and have been associated with increased mortality. To understand these findings, we performed a meta-analysis of results from four phase 3 trials.

SUBJECTS AND METHODS

Trials were identified by MEDLINE search; review of abstracts from American College of Cardiology, European Society of Cardiology, and American Heart Association scientific sessions; or querying investigators in the field. Published, phase 3, randomized, placebo-controlled trials involving more than 1000 patients with coronary artery disease that compared an oral glycoprotein IIb/IIIa antagonist with or without background aspirin versus aspirin, and that had a planned follow-up of > or =30 days, were included. Four trials met these criteria. Odds ratios (ORs) and 95% confidence intervals (CIs) were generated from results, and combined using an empirical Bayes random-effects model.

RESULTS

Among 33,326 patients, oral glycoprotein IIb/IIIa agents were associated with 31% increased mortality (OR = 1.31; 95% CI: 1.12 to 1.53; P= 0.0001). Results were similar whether the agent was added to (OR = 1.38; 95% CI: 1.15 to 1.67) or substituted for (OR = 1.37; 95% CI: 1.00 to 1.86) aspirin. Ischemic events or sudden death (OR = 1.22; 95% CI: 0.91 to 1.63) were also more common. Among patients with acute coronary syndromes, the incidence of myocardial infarction was increased (OR = 1.16; 95% CI: 1.03 to 1.29).

CONCLUSION

Oral glycoprotein IIb/IIIa inhibitor therapy is associated with increased mortality and myocardial infarction. No single explanation for these findings is satisfactory; the problem is likely to be multifactorial.

Rationale for the use of platelet aggregation inhibitors in PAD patients

Peripheral arterial disease (PAD) is a major risk marker for systemic ischaemic events. The understanding of PAD has moved from PAD as an organ-specific disease to PAD as the lower-limb localization of a multifocal disease, i.e. atherothrombosis. Blood platelet activation and aggregation is a common denominator in atherothrombotic events, and use of antiplatelet agents in patients with PAD can inhibit thrombus formation and reduce the occurrence of myocardial infarction (MI), ischaemic stroke (IS) and vascular death. Many studies have investigated various antiplatelet regimens for preventing acute cardiovascular events in patients with a prior ischaemic event, although many of these studies had a number of limitations. The Antiplatelet Trialists' Collaboration performed a meta-analysis of 23 stroke trials and found an average odds risk reduction of 25% for a combined endpoint of stroke, MI or vascular death. The concept of atherothrombosis as a multifocal disease was challenged by the Clopidogrel versus Aspirin in Patients at Risk of Ischaemic Events (CAPRIE) trial. This study showed an 8.7% decrease in the relative risk reduction for further atherothrombotic events with clopidogrel over aspirin (p = 0.043) for the overall population, in terms of the combined endpoint of IS, Ml or vascular death.

Persistence of the prothrombotic state after acute coronary syndromes: implications for treatment

BACKGROUND AND RESULTS

Acute coronary syndromes (unstable angina and acute myocardial infarction) are generally caused by thrombosis over a disrupted atherosclerotic plaque. During the acute phase, antithrombotic therapy (including aspirin and heparin) has been shown to reduce the risk of death or myocardial infarction (MI). The purpose of this review is to examine the high-risk period for clinical thrombotic events that extends for several weeks after presentation and to review the treatments aimed at reducing these events.

RESULTS

More than half of clinical events reported during the first month occur after the first 3 to 5 days that comprise the standard in-hospital treatment period. Several different antithrombotic approaches have been tested, including longer duration of antiplatelet therapy, anticoagulant treatment, and oral glycoprotein (GP) IIb/IIIa inhibitors. Aspirin is effective at reducing risk, and clopidogrel provides additional benefit, as does dalteparin for at least the first month. Warfarin in addition to aspirin, while generally disappointing, has not been adequately tested at higher doses. Oral GP IIb/IIIa inhibitors cause a paradoxic increased risk of death for unclear reasons.

CONCLUSION

Further reduction of risk during the weeks after presentation with acute coronary syndromes remains an important therapeutic goal.

Selection of anticoagulants or antiplatelet-aggregating agents for prevention of stroke

Stroke is one of leading causes of mortality and morbidity in the United States. Stroke prevention includes treatment of the stroke risk factors and long-term use of antithrombotic agents. Various agents have been studied for stroke prevention and other trials are ongoing. The aim of this article is to provide an overview of the recent guidelines, recommendations, and clinical trial results using antithrombotic therapy for stroke prevention.

The nonpeptide glycoprotein IIb/IIIa platelet receptor antagonist SM-20302 reduces tissue plasminogen activator-induced intracerebral hemorrhage after thromboembolic stroke

BACKGROUND AND PURPOSE

Platelet activation and deposition in brain microvessels appear to be key events in the pathogenesis of ischemia-induced neuronal degeneration and behavioral deficits. It has been hypothesized that activated platelets in combination with polymorphonuclear leukocytes and fibrin may play a role in vessel reocclusion leading to the "no-reflow" phenomenon after administration of the thrombolytic tissue plasminogen activator (tPA). We studied the effects of the novel glycoprotein IIb/IIIa platelet receptor antagonist SM-20302 when administered in combination with tPA on infarct and hemorrhage rate and volume to determine whether activated platelets are involved in either infarct or hemorrhage generation after a thromboembolic stroke.

METHODS

One hundred thirty-two male New Zealand White rabbits were included in the present study. Rabbits were embolized by injecting a blood clot into the middle cerebral artery via a catheter. Five or 65 minutes after embolization, SM-20302 (5 mg/kg) was infused intravenously. In drug combination studies, tPA was infused intravenously for 30 minutes starting 60 minutes after embolization, and SM-20302 was administered 5 or 65 minutes after embolization. Postmortem analysis included assessment of hemorrhage, infarct size and location, and clot lysis.

RESULTS

In the vehicle control group, the hemorrhage rate after a thromboembolic stroke was 33%. There was a significant increase (109%) in the hemorrhage rate in the group of rabbits treated with the thrombolytic tPA. SM-20302 by itself did not significantly alter the embolism-induced hemorrhage rate when administered either 5 or 65 minutes after embolism. The SM-20302 groups had a 42% and 33% incidence of hemorrhage in the 5- and 65-minute groups, respectively. In groups treated with a combination of drugs, the SM-20302/tPA group had a 31% and 71% incidence of hemorrhage when SM-20302 was administered 5 and 65 minutes after embolization, respectively. SM-20302 in combination with tPA also significantly increased infarct rate, but not hemorrhage or infarct volume.

CONCLUSIONS

This study suggests that treatment of thromboembolic stroke with the combination of a platelet inhibitor and tPA may have a beneficial outcome on the basis of the following: First, acute administration of SM-20302 did not significantly increase hemorrhage rate. Second, SM-20302 in combination with tPA significantly reduced tPA-induced intracerebral hemorrhage. Third, there appears to be a specific window of opportunity when a platelet inhibitor must be administered to produce a beneficial effect. Overall, on the basis of our results, we hypothesize that the increased rate of intracerebral hemorrhage observed after tPA administration may be partly due to increased reocclusion of cerebral vessels following lysis of the emboli and that reocclusion can be controlled by administration of a platelet inhibitor.

Hemorrhagic transformation following ischemic stroke: significance, causes, and relationship to therapy and treatment

Hemorrhagic transformation (HT) is a frequent consequence of ischemic stroke that becomes more prevalent after thrombolytic therapy. Despite concerns about safety parameters, thrombolytic drugs remain the first course of action available to clinicians for stroke management. However, recent efforts in preclinical studies have attempted to discover other drugs that can lessen the risk of hemorrhage associated with thrombolytic administration. This review focuses on three classes of pharmacologic agents that have shown some promise in animal models of stroke, and can thus be considered as possible candidates for coadministration with thrombolytics in the treatment of stroke. These include the following: 1) spin trap agents, such as alpha-phenyl-N-t-butylnitrone (PBN) that scavenge free radicals; 2) matrix metalloproteinase (MMP) inhibitors, such as BB-94, that prevent membrane and vessel remodeling following ischemia; and 3) the novel glycoprotein (GP) IIb/IIIa platelet receptor antagonist SM-20302. Although these drugs affect different mechanisms, the common denominator seemed to be their effectiveness in reducing the incidence of hemorrhage in response to thrombolytic infusion following an embolic stroke.

Optimal treatment and current situation in reperfusion after thrombolysis for acute myocardial infarction

Acute myocardial infarction is the leading cause of death in the industrialized world and the paramount goal is establishing early, complete, and sustained reperfusion at the myocardial tissue level. For hospitals without the capacity to perform emergent percutaneous coronary intervention, fibrinolytic therapy plays a critical role although it is limited by a 67% success rate. Despite promising pilot studies, reduced-dose fibrinolytic therapy with glycoprotein IIb/IIIa therapy (GUSTO-V) and full-dose fibrinolytic therapy with enoxaparin (ASSENT-3) or bivalirudin (HERO-2) provide only marginally improved clinical outcomes. Adjunctive in-hospital and secondary preventive measures should include an aspirin, a beta-blocker, an ACE inhibitor, and a statin, based on the Heart Protection Study, unless contraindicated. Patients should be risk stratified, participate in a cardiac rehabilitation program, cease smoking tobacco, and have an intracardiac defibrillator (ICD) implanted if their LV systolic function is < or = 30% at one month based on the MADIT-2 trial.

Intra-arterial thrombin injection of an ascending aortic pseudoaneurysm complicated by transient ischemic attack and rescued with systemic abciximab

Thrombin injection as a means of inducing thrombus formation has recently received wide attention as an alternative treatment for pseudoaneurysm. We present a case of a 67-year-old man in whom a large mycotic pseudoaneurysm developed in the ascending aorta because of sternal osteomyelitis and mediastinitis after coronary artery bypass grafting. Transcatheter intra-arterial thrombin injection was performed, and it successfully induced pseudoaneurysm thrombosis. However, the procedure was complicated by a sudden transient ischemic attack caused by thrombus propagation into the cerebral circulation. Complete thrombus dissolution in the cerebral circulation with the resolution of neurologic symptoms was achieved by means of intravenous abciximab.

Therapeutic potential of GP IIb/IIIa receptor antagonists in acute myocardial infarction

The management of acute myocardial infarction (AMI) has changed dramatically over the last two decades, with the addition of fibrinolytic agents and primary coronary intervention (PCI). The more recent development of the glycoprotein (GP) IIb/IIIa antagonists, a new class of potent antiplatelet drugs, has the potential to considerably enhance the treatment of AMI patients. A number of recent studies have highlighted the potential incremental benefits with adjunctive IIb/IIIa-targeted therapy. In this review, we will discuss the pathophysiology of myocardial infarction (MI), the physiology and role of platelets in thrombosis and describe the currently available drugs. We will briefly summarise the results of recent clinical trials, discuss some key forthcoming trials and attempt to describe how GP IIb/IIIa antagonists may directly impact the immediate and near future day-to-day care of patients with AMI.

Antiplatelet agents for secondary prevention of ischemic stroke

OBJECTIVE

To review and summarize the efficacy, mechanisms of action, and cost of the options available when choosing antiplatelet agents for secondary stroke prevention.

DATA SOURCES

This article is based on a review of the literature found with MEDLINE, CINAHL, and Cochrane Reviews (1980-June 2000) and abstracts from relevant international scientific meetings. We searched for the terms aspirin, ticlopidine, dipyridamole, antiplatelet, and clopidogrel.

STUDY SELECTION

English-language articles, both reviews and original studies, were evaluated, and all information considered relevant was included in this review. In addition, guidelines from the American Heart Association are included.

DATA SYNTHESIS

Aspirin is a relatively inexpensive and effective agent for secondary stroke prevention, and lower doses of aspirin appear as effective as higher doses. Ticlopidine has been used alone or in combination with aspirin, but serious adverse effects have limited its use. Clopidogrel has emerged as a safe and effective alternative to ticlopidine and lacks some of the serious adverse effects associated with ticlopicine, but is not superior to aspirin in secondary stroke prevention. Unlike previous studies, one recent trial showed that dipyridamole in combination with aspirin is superior to aspirin alone.

CONCLUSIONS

Antiplatelet therapy is a key component of secondary prevention strategies in ischemic stroke. While aspirin has been the cornerstone in the management of stroke, other classes of antiplatelet drugs present new opportunities to optimize antiplatelet therapy.

Antiplatelet therapy in secondary stroke prevention

Stroke is the third leading cause of death in the United States. Antiplatelet agents are the mainstays of ischaemic stroke prevention. The therapies recommended for initial therapy include aspirin (50 - 325 mg) daily, the combination of aspirin (25 mg) and extended-release dipyridamole (200 mg) b.i.d., or clopidogrel (75 mg) daily. Ticlopidine 250 mg b.i.d. is approved for stroke prevention but is no longer a first-line therapy. This article reviews the literature on antiplatelet agents for secondary stroke prevention.

Antithrombotic Secondary Prevention After Stroke

In patients with transient ischemic attack (TIA) or ischemic stroke of noncardiac origin, antiplatelet drugs are able to decrease the risk of stroke by 11% to 15%, and decrease the risk of stroke, myocardial infarction (MI), and vascular death by 15% to 22%. Aspirin leads to a moderate but significant reduction of stroke, MI, and vascular death in patients with TIA and ischemic stroke. Low doses are as effective as high doses, but are better tolerated in term of gastrointestinal side effects. The recommended aspirin dose, therefore, is between 50 and 325 mg. Bleeding complications are not dose-dependent, and also occur with the lowest doses. The combination of aspirin (25 mg twice daily) with slow release dipyridamole (200 mg twice daily) is superior compared with aspirin alone for stroke prevention. Ticlopidine is effective in secondary stroke prevention in patients with TIA and stroke. For some endpoints, it is superior to aspirin. Due to its side effect profile (neutropenia, thrombotic thrombocytopenic purpura ), ticlopidine should be given to patients who are intolerant of aspirin. Prospective trials have not indicated whether ticlopidine is suggested for patients who have recurrent cerebrovascular events while on aspirin. Clopidogrel has a better safety profile than ticlopidine. Although not investigated in patients with TIA, clopidogrel should also be effective in these patients assuming the same pathophysiology than in patients with stroke. Clopidogrel is second-line treatment in patients intolerant for aspirin, and first-line treatment for patients with stroke and peripheral arterial disease or MI. A frequent clinical problem is patients who are already on aspirin because of coronary heart disease or a prior cerebral ischemic event, and then suffer a first or recurrent TIA or stroke. No single clinical trial has investigated this problem. Therefore, recommendations are not evidence-based. Possible strategies include the following: continue aspirin, add dipyridamole, add clopidogrel, switch to ticlopidine or clopidogrel, or switch to anticoagulation with an International Normalized Ratio (INR) of 2.0 to 3.0. The combination of low-dose warfarin and aspirin was never studied in the secondary prevention of stroke. In patients with a cardiac source of embolism, anticoagulation is recommended with an INR of 2.0 to 3.0. At the present time, anticoagulation with an INR between 3.0 and 4.5 can not be recommended for patients with noncardiac TIA or stroke. Anticoagulation with an INR between 3.0 and 4.5 carries a high bleeding risk. Whether anticoagulation with lower INR is safe and effective is not yet known. Treatment of vascular risk factors should also be performed in secondary stroke prevention.

Adjunctive pharmacotherapy for coronary stenting

The use of coronary stents improves the outcomes of percutaneous coronary intervention (PCI). This has led to a rapid increase in their use. Coronary stenting is not without problems and is complicated by both early ischemic events and late restenosis. The combination of anticoagulation with unfractionated heparin (UFH) and the use of antiplatelet agents including aspirin, thienopyridines, and glycoprotein IIb/IIIa inhibitors has led to a major reduction in early ischemic events after stenting. Low molecular weight heparin (LMWH) and direct thrombin inhibitors have a number of theoretical advantages over UFH. Their role as an adjunct to coronary stenting is still under investigation. Trials of systemic pharmacotherapy aimed at reducing in-stent restenosis have been consistently disappointing. Preliminary results of stents coated with agents that inhibit neointimal proliferation are extremely promising. The results of ongoing phase III trials of these coated stents are eagerly awaited.

Current oral antiplatelet agents to prevent atherothrombosis

Aspirin inhibits platelet activation by irreversibly inhibiting platelet cyclooxygenase and thromboxane production, and reduces the odds of serious vascular events (stroke, myocardial infarction or vascular death) by about one quarter in a range of patients with symptomatic atherosclerosis at high risk of a subsequent event. The adenosine diphosphate (ADP) receptor antagonists clopidogrel and ticlopidine are significantly more effective than aspirin in high-risk vascular patients, further reducing the odds of serious vascular events by about 10% (95% CI 2-19%) over the benefit provided by aspirin. The ADP receptor antagonists are also associated with a significant 30% reduction in the odds of gastrointestinal haemorrhage (odds ratio 0.71, 95% CI 0.59-0.86). Ticlopidine increases the odds of skin rash and of diarrhoea by more than twofold compared with aspirin, whereas clopidogrel is associated with a one-third increase in the odds of rash and of diarrhoea. Only ticlopidine increases the odds of neutropenia compared with aspirin. There is no clear evidence as yet for the benefit of dipyridamole or an oral GP IIb/IIIa receptor antagonist as single antiplatelet agents in atherothrombotic patients. Amongst high vascular risk patients, the combination of low-dose aspirin and high-dose dipyridamole is associated with about a 10% (95% CI 0-20%) reduction in the odds of a serious vascular event. Most of this reduction is due to a 23% reduction in non-fatal stroke. The size of this estimate continues to be investigated in an ongoing study of patients with transient ischaemic attack and stroke. The combined use of aspirin and ticlopidine is markedly superior to heparin, warfarin and aspirin for reducing thrombotic complications after coronary artery stenting. Clopidogrel plus aspirin has been shown to be safer than aspirin and ticlopidine in coronary stenting, and is now under long-term evaluation in unstable angina, and other conditions in which patients are at high risk of atherothrombotic events.

Platelet glycoprotein IIb/IIIa receptor blockade in coronary artery disease

Glycoprotein IIb/IIIa inhibitors represent a new promising class of antiplatelet medications. Their use in acute coronary syndromes and for patients undergoing percutaneous coronary intervention has been the subject of a number of large controlled trials using both the intravenous and the oral forms. In this review, we present a systematic overview of these trials.

Oral glycoprotein IIb/IIIa antagonists in coronary artery disease

Despite the efficacy of intravenous glycoprotein IIb/IIIa inhibition in patients undergoing percutaneous coronary intervention and those presenting with acute coronary syndromes, the application of oral glycoprotein IIb/IIIa inhibition to the chronic management of coronary artery disease has not met with the same success. To explain these results, factors related to dosing, and inadequate inhibition or activation of platelet pro-coagulant activity have been recently suggested. However, although the disparity between intravenous and oral glycoprotein IIb/IIIa experience remains largely enigmatic, the discordant effect on ischemic endpoints observed within the phase III oral glycoprotein IIb/IIIa inhibitor trials potentially implicates a mechanism unrelated to platelet function.

Lotrafiban: an oral platelet glycoprotein IIb/IIIa blocker

Platelets play a major role in thrombus formation, as well as in the pathogenesis of atherothrombosis. Inhibition of platelet function is now emphasised more than ever for prevention and treatment of almost all vascular diseases, since thrombosis is established as the key pathogenic event causing acute ischaemic coronary and cerebrovascular syndromes. Although acetylsalicylic acid (aspirin) has been shown to reduce the incidence of myocardial infarction and stroke, its effect is weak and more effective antithrombotic agents are required to manage patients at high-risk for recurrent vascular events. Platelet glycoprotein IIb/IIIa receptor (GPIIb/IIIa) blockade represents a significant advance in interventional cardiology and treatment of acute ischaemic syndromes. The past several years have seen the introduction of many platelet GPIIb/IIIa blockers into the clinical arena targeting the unique platelet GPIIb/IIIa receptor for the adhesive proteins, fibrinogen and von Willebrand Factor. Platelet GPIIb/IIIa blockers administered intravenously have proven efficacious in mitigating arterial thrombosis in acute coronary syndromes (unstable angina and non-ST-elevation myocardial infarction) and percutaneous coronary interventions (PCI) such as balloon dilatation and stent implantation. Currently, orally-active platelet GPIIb/IIIa blockers are being developed to provide additional benefits for primary and secondary prevention of thrombosis as chronic treatment, especially in high-risk patients. Lotrafiban (SmithKline Beecham) is a member of the latest generation of orally-active platelet GPIIb/IIIa blockers undergoing Phase III clinical trials to test the relative effectiveness versus other oral platelet inhibitors for ischaemic conditions including unstable angina, restenosis after PCI and stroke. Lotrafiban is converted from an esterified prodrug by plasma and liver esterases to a peptidomimetic of the arginine-glycine-aspartic acid amino acid sequence. This sequence itself mimics the binding site of fibrinogen and von Willebrand Factor to the platelet GPIIb/IIIa receptor. Preliminary results of the clinical trial APLAUD (antiplatelet useful dose) show that lotrafiban is clinically safe and well-tolerated in patients with recent myocardial infarction, unstable angina, transient ischaemic attack (TIA), or stroke when added to aspirin therapy. With lotrafiban, a worldwide large-scale Phase III clinical trial BRAVO (blockage of the GPIIb/IIIa receptor to avoid vascular occlusion) is currently underway. In general, GPIIb/IIIa blockade seems clinically very promising. A number of unresolved issues, however, remain to be elucidated.