Disposition of 14C-eptifibatide after intravenous administration to healthy men

Bleeding Complications After Breast Core-needle Biopsy-An Approach to Managing Patients on Antithrombotic Therapy

Image-guided core-needle breast and axillary biopsy (CNB) is the standard-of-care procedure for the diagnosis of breast cancer. Although the risks of CNB are low, the most common complications include bleeding and hematoma formation. Post-procedural bleeding is of particular concern in patients taking antithrombotic therapy, but there is currently no widely established standard protocol in the United States to guide antithrombotic therapy management. In the face of an increasing number of patients taking antithrombotic therapy and with the advent of novel classes of anticoagulants, the American College of Radiology guidelines recommend that radiologists consider cessation of antithrombotic therapy prior to CNB on a case-by-case basis. Lack of consensus results in disparate approaches to patients on antithrombotic therapy undergoing CNB. There is further heterogeneity in recommendations for cessation of antithrombotic therapy based on the modality used for image-guided biopsy, target location, number of simultaneous biopsies, and type of antithrombotic agent. A review of the available data demonstrates the safety of continuing antithrombotic therapy during CNB while highlighting additional procedural and target lesion factors that may increase the risk of bleeding. Risk stratification of patients undergoing breast interventional procedures is proposed to guide both pre-procedural decision-making and post-procedural management. Radiologists should be aware of antithrombotic agent pharmacokinetics and strategies to minimize post-procedural bleeding to safely manage patients.

Management of Anticoagulant and Antiplatelet Medications in Adults Undergoing Percutaneous Interventions

OBJECTIVE

Many radiologists are unfamiliar with the new antithrombogenic medications and how to modify patient management before nonvascular percutaneous procedures performed in a radiology department. In this article, we review the indications for use, mechanism of action, pharmacokinetics, dosing, and recommendations for periprocedural management of patients using these medications.

CONCLUSION

To improve patient safety, radiologists involved in percutaneous procedures should have knowledge of the antithrombotics that will be encountered routinely in clinical practice.

Pharmacokinetics and pharmacokinetic-pharmacodynamic correlations of therapeutic peptides

Peptides, defined as polymers of less than 50 amino acids with a molecular weight of less than 10 kDa, represent a fast-growing class of new therapeutics which has unique pharmacokinetic characteristics compared to large proteins or small molecule drugs. Unmodified peptides usually undergo extensive proteolytic cleavage, resulting in short plasma half-lives. As a result of their low permeability and susceptibility to catabolic degradation, therapeutic peptides usually have very limited oral bioavailability and are administered either by the intravenous, subcutaneous, or intramuscular route, although other routes such as nasal delivery are utilized as well. Distribution processes are mainly driven by a combination of diffusion and to a lesser degree convective extravasation dependent on the size of the peptide, with volumes of distribution frequently not larger than the volume of the extracellular body fluid. Owing to the ubiquitous availability of proteases and peptidases throughout the body, proteolytic degradation is not limited to classic elimination organs. Since peptides are generally freely filtered by the kidneys, glomerular filtration and subsequent renal metabolism by proteolysis contribute to the elimination of many therapeutic peptides. Although small peptides have usually limited immunogenicity, formation of anti-drug antibodies with subsequent hypersensitivity reactions has been described for some peptide therapeutics. Numerous strategies have been applied to improve the pharmacokinetic properties of therapeutic peptides, especially to overcome their metabolic instability, low permeability, and limited tissue residence time. Applied techniques include amino acid substitutions, modification of the peptide terminus, inclusion of disulfide bonds, and conjugation with polymers or macromolecules such as antibody fragments or albumin. Application of model-based pharmacokinetic-pharmacodynamic correlations has been widely used for therapeutic peptides in support of drug development and dosage regimen design, especially because their targets are often well-described endogenous regulatory pathways and processes.

The kinetics of integrilin limited by obesity: a multicenter randomized pharmacokinetic and pharmacodynamic clinical trial

BACKGROUND

KILO tested 2 novel weight-based eptifibatide dosing strategies compared with standard dosing in obese patients undergoing elective percutaneous coronary intervention (PCI). Eptifibatide dosing is weight adjusted for patients up to 121 kg. Patients above this weight receive the same maximal dose, although it is unknown if this provides adequate eptifibatide concentration or platelet inhibition.

METHODS

Sixty-seven patients weighing ≥125 kg undergoing elective PCI were randomized to 1 of 3 eptifibatide dosing regimens: standard dosing using a weight of 121 kg, actual body weight (ABW)-based dosing with no upper limit, or ideal body weight (IBW)-based dosing. Boluses of 180 μg/kg were given 10 minutes apart, followed by a 2.0 μg/kg per minute infusion. Plasma eptifibatide concentrations were drawn at 12 to 18 hours after initiating the infusion. Platelet aggregation was assessed at baseline and 10 minutes after the second bolus.

RESULTS

Sixty-seven patients were randomized to standard (n = 22), ABW (n = 23), or IBW (n = 22) dosing. The median (25th, 75th) steady-state plasma eptifibatide concentrations were 1,740 ng/mL (1,350, 2,350), 1,780 ng/mL (1,510, 2,350), and 1,055 ng/mL (738, 1,405), respectively (P < .001). Ten-minute median (25th, 75th) platelet aggregation units were 7 (0, 21), 2 (0, 8), and 14 (8, 20), respectively (P = .001).

CONCLUSIONS

Actual body weight eptifibatide dosing leads to higher plasma concentrations and greater platelet inhibition than standard or IBW dosing in obese patients undergoing PCI. Current recommendations for eptifibatide dosing may be inadequate in patients >121 kg. Further study is warranted to define the optimal dosing of eptifibatide and other medications in obese patients.

Making the right choice: optimizing rt-PA and eptifibatide lysis, an in vitro study

INTRODUCTION

Recombinant tissue plasminogen activator (rt-PA) is the only FDA approved lytic therapy for acute ischemic stroke. However, there can be complications such as intra-cerebral hemorrhage. This has led to interest in adjuncts such as GP IIb-IIIa inhibitors. However, there is little data on combined therapies. Here, we measure clot lysis for rt-PA and eptifibatide in an in vitro human clot model, and determine the drug concentrations maximizing lysis. A pharmacokinetic model is used to compare drug concentrations expected in clinical trials with those used here. The hypothesis is that there is a range of rt-PA and eptifibatide concentrations that maximize in vitro clot lysis.

MATERIALS AND METHODS

Whole blood clots were made from blood obtained from 28 volunteers, after appropriate institutional approval. Sample clots were exposed to rt-PA and eptifibatide in human fresh-frozen plasma; rt-PA concentrations were 0, 0.5, 1, and 3.15 μg/ml, and eptifibatide concentrations were 0, 0.63, 1.05, 1.26 and 2.31 μg/ml. All exposures were for 30 minutes at 37 C. Clot width was measured using a microscopic imaging technique and mean fractional clot loss (FCL) at 30 minutes was used to determine lytic efficacy. On average, 28 clots (range: 6-148) from 6 subjects (3-24) were used in each group.

RESULTS AND CONCLUSIONS

FCL for control clots was 14% (95% Confidence Interval: 13-15%). FCL was 58% (55-61%) for clots exposed to both drugs at all concentrations, except those at an rt-PA concentration of 3.15 μg/ml, and eptifibatide concentrations of 1.26 μg/ml (Epf) or 2.31 μg/ml. Here, FCL was 43% (36-51) and 35% (32-38) respectively. FCL is maximized at moderate rt-PA and eptifibatide concentration; these values may approximate the average concentrations used in some rt-PA and eptifibatide treatments.

Safety, pharmacokinetic and pharmacodynamic studies of batifiban injection following single- and multiple-dose administration to healthy Chinese subjects

Batifiban, a synthetic cyclic peptide, is a potent platelet glycoprotein GPIIb/IIIa antagonist which may be useful in the treatment and prevention of acute coronary syndromes. The pharmacokinetics and pharmacodymanic (inhibition of platelet aggregation) effects, and tolerability of batifiban were investigated in healthy subjects following single bolus injection with doses of 55, 110, or 220 microg/kg, or multiple doses of an bolus followed intravenous infusion for 24 h (180 microg/kg plus 2.0 microg/min.kg, and 220 microg/kg plus 2.5 microg/min.kg) in this phase I clinical trial. Plasma levels of batifiban and areas under the curve were found to be proportional to doses. Batifiban was rapidly eliminated with a half-life of approximately 2.5 h. Significant differences were noted for plasma levels of batifiban and areas under the curve between males and females. No significant differences in the terminal half-life were found between males and females. Batifiban reversibly inhibited ex vivo platelet aggregation in a dose- and concentration-dependent manner, consistent with its mechanism as a GPIIb/IIIa antagonist. Single and multiple intravenous doses of batifiban were found to be safe and well tolerated in healthy subjects. These results support a bolus injection plus intravenous infusion regimen of batifiban for the treatment and prevention of acute coronary syndromes.

Use of Low Molecular Weight Heparins and Glycoprotein IIb/IIIa Inhibitors in Patients with Chronic Kidney Disease

Despite aggressive intervention, cardiac causes of death, including acute coronary syndrome (ACS), continue to be a major source of mortality in patients with chronic kidney disease (CKD), including end-stage renal disease (ESRD). Multiple large prospective trials have demonstrated the clinical benefits of both low molecular weight heparin (LMWH) and glycoprotein (Gp) IIb/IIIa inhibitors in treating patients with ACS. Unfortunately patients with significant impairment of kidney function have generally been excluded from these major clinical trials. Consequently relatively little is known about the pharmacokinetics, appropriate dosing, efficacy, and safety of these medications in patients with CKD of various stages. This article examines the available literature regarding the pharmacokinetics, dosing, efficacy, and safety of LMWH and Gp IIb/IIIa inhibitors in patients with CKD.

What is the Objective of the Mass Balance Study? A Retrospective Analysis of Data in Animal and Human Excretion Studies Employing Radiolabeled Drugs

Mass balance excretion studies in laboratory animals and humans using radiolabeled compounds represent a standard part of the development process for new drugs. From these studies, the total fate of drug-related material is obtained: mass balance, routes of excretion, and, with additional analyses, metabolic pathways. However, rarely does the mass balance in radiolabeled excretion studies truly achieve 100% recovery. Many definitions of cutoff criteria for mass balance that identify acceptable versus unacceptable recovery have been presented as ad hoc statements without a strong rationale. To address this, a retrospective analysis was undertaken to explore the overall performance of mass balance studies in both laboratory animal species and humans using data for 27 proprietary compounds within Pfizer and extensive review of published studies. The review has examined variation in recovery and the question of whether low recovery was a cause for concern in terms of drug safety. Overall, mean recovery was greater in rats and dogs than in humans. When the circulating half-life of total radioactivity is greater than 50 h, the recovery tends to be lower. Excretion data from the literature were queried as to whether drugs linked with toxicities associated with sequestration in tissues or covalent binding exhibit low mass balance. This was not the case, unless the sequestration led to a long elimination half-life of drug-related material. In the vast majority of cases, sequestration or concentration of drug-related material in an organ or tissue was without deleterious effect and, in some cases, was related to the pharmacological mechanism of action. Overall, from these data, recovery of radiolabel would normally be equal to or greater than 90%, 85%, and 80% in rat, dog, and human, respectively. Since several technical limitations can underlie a lack of mass balance and since mass balance data are not sensitive indicators of the potential for toxicity arising via tissue sequestration, absolute recovery in humans should not be used as a major decision criteria as to whether a radiolabeled study has met its objectives. Instead, the study should be seen as an integral part of drug development answering four principal questions: 1) Is the proposed clearance mechanism sufficiently supported by the identities of the drug-related materials in excreta, so as to provide a complete understanding of clearance and potential contributors to interpatient variability and drug-drug interactions? 2) What are the drug-related entities present in circulation that are the active principals contributing to primary and secondary pharmacology? 3) Are there findings (low extraction recovery of radiolabel from plasma, metabolite structures indicative of chemically reactive intermediates) that suggest potential safety issues requiring further risk assessment? 4) Do questions 2 and 3 have appropriate preclinical support in terms of pharmacology, safety pharmacology, and toxicology? Only if one or more of these four questions remain unanswered should additional mass balance studies be considered.

Antiplatelet drugs: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This article about currently available antiplatelet drugs is part of the Antithrombotic and Thrombolytic Therapy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). It describes the mechanism of action, pharmacokinetics, and pharmacodynamics of aspirin, reversible cyclooxygenase inhibitors, thienopyridines, and integrin alphaIIbbeta3 receptor antagonists. The relationships among dose, efficacy, and safety are thoroughly discussed, with a mechanistic overview of randomized clinical trials. The article does not provide specific management recommendations; however, it does highlight important practical aspects related to antiplatelet therapy, including the optimal dose of aspirin, the variable balance of benefits and hazards in different clinical settings, and the issue of interindividual variability in response to antiplatelet drugs.

Management of antiplatelet therapy for minimization of bleeding risk before cardiac surgery

Antiplatelet therapy is commonly administered for primary and secondary prevention of stroke, recurrent angina, myocardial infarction, and death in patients with cardiovascular disorders. It also is associated with an increased risk of bleeding. We describe the management of antiplatelet therapy in patients undergoing coronary artery bypass graft surgery. In addition, we provide basic information about the mechanisms of action by which the most common antiplatelet agents inhibit platelet function. This information is integrated with results from pharmacologic studies and clinical trials. Determining the net effect in patients undergoing coronary artery bypass graft surgery requires knowledge about the pharmacokinetics, pharmacodynamics, and clinical efficacy of each drug, and an estimation of the absolute thrombotic versus hemorrhagic risk for each patient.

Pharmacokinetic aspects of biotechnology products

In recent years, biotechnologically derived peptide and protein-based drugs have developed into mainstream therapeutic agents. Peptide and protein drugs now constitute a substantial portion of the compounds under preclinical and clinical development in the global pharmaceutical industry. Pharmacokinetic and exposure/response evaluations for peptide and protein therapeutics are frequently complicated by their similarity to endogenous peptides and proteins as well as protein nutrients. The first challenge frequently comes from a lack of sophistication in various analytical techniques for the quantification of peptide and protein drugs in biological matrices. However, advancements in bioassays and immunoassays--along with a newer generation of mass spectrometry-based techniques--can often provide capabilities for both efficient and reliable detection. Selection of the most appropriate route of administration for biotech drugs requires comprehensive knowledge of their absorption characteristics beyond physicochemical properties, including chemical and metabolic stability at the absorption site, immunoreactivity, passage through biomembranes, and active uptake and exsorption processes. Various distribution properties dictate whether peptide and protein therapeutics can reach optimum target site exposure to exert the intended pharmacological response. This poses a potential problem, especially for large protein drugs, with their typically limited distribution space. Binding phenomena and receptor-mediated cellular uptake may further complicate this issue. Elimination processes--a critical determinant for the drug's systemic exposure--may follow a combination of numerous pathways, including renal and hepatic metabolism routes as well as generalized proteolysis and receptor-mediated endocytosis. Pharmacokinetic/pharmacodynamic (PK/PD) correlations for peptide and protein-based drugs are frequently convoluted by their close interaction with endogenous substances and physiologic regulatory feedback mechanisms. Extensive use of pharmacokinetic and exposure/response concepts in all phases of drug development has in the past been identified as a crucial factor for the success of a scientifically driven, evidence-based, and thus accelerated drug development process. Thus, PK/PD concepts are likely to continue and expand their role as a fundamental factor in the successful development of biotechnologically derived drug products in the future.

Platelet-Active Drugs: The Relationships Among Dose, Effectiveness, and Side Effects

This article discusses platelet active drugs as part of the Seventh American College of Chest Physicians Conference on Antithrombotic and Thrombolytic Therapy: Evidence-Based Guidelines. New data on antiplatelet agents include the following: (1) the role of aspirin in primary prevention has been the subject of recommendations based on the assessment of cardiovascular risk; (2) an increasing number of reports suggest a substantial interindividual variability in the response to antiplatelet agents, and various phenomena of "resistance" to the antiplatelet effects of aspirin and clopidogrel; (3) the benefit/risk profile of currently available glycoprotein IIb/IIIa antagonists is substantially uncertain for patients with acute coronary syndromes who are not routinely scheduled for early revascularization; (4) there is an expanding role for the combination of aspirin and clopidogrel in the long-term management of high-risk patients; and (5) the cardiovascular effects of selective and nonselective cyclooxygenase-2 inhibitors have been the subject of increasing attention.

A perspective on the toxicological mechanisms possibly contributing to the failure of oral glycoprotein IIb/IIIa antagonists in the clinic

In clinical trials in patients with acute or unstable coronary syndromes and/or undergoing percutaneous coronary intervention, oral glycoprotein (GP) IIb/IIIa antagonists did not show therapeutic benefit over aspirin during long-term administration. Moreover, high-dose oral administration of these agents was associated with greater fatality risk compared with that of lower doses. This article postulates that continuous exposure of the GP IIb/IIIa receptor (integrin alpha(IIb)beta(3)) to these agents may result in some form of resistance or activation of other biological systems. These toxicological mechanisms may help explain some factors that could potentially contribute to the failure of these agents in clinical trials. Several hypotheses are presented: (i) modulation of platelet response because of long-term exposure to GP IIb/IIIa antagonists; (ii) role of related integrins and associated proteins to compensate for the loss of platelet activity because of dysfunctional GP IIb/IIIa receptors occupied by inhibitors; (iii) effects of the GP IIb/IIIa antagonists on other cellular systems such as the caspase and procaspase enzymes in apoptosis and possibly the ryanodine receptor involved in sarcoplasmic reticulum calcium release. These toxicological mechanisms could potentially limit the utility of these oral agents in long-term administration.

Therapeutic use of intravenous eptifibatide in patients undergoing percutaneous coronary intervention: acute coronary syndromes and elective stenting

Eptifibatide, a molecule isolated from the venom of the southeastern pygmy rattlesnake, selectively inhibits the platelet receptor IIb/IIIa. The safety and clinical efficacy of eptifibatide in patients undergoing percutaneous coronary intervention (PCI) was first evaluated in the Integrilin to Minimize Platelet Aggregation and Coronary Thrombosis (IMPACT) trial. In this study, the primary combined endpoint (composite of death, myocardial infarction [MI] or target vessel revascularization [TVR] at 30 days) occurred in 9.6% of the patients assigned to eptifibatide bolus followed by the 4-hour infusion versus 12.2% in the placebo group (p = 0.67). In the IMPACT-II trial, two different eptifibatide dosages were studied in 4011 patients undergoing elective PCI. The primary endpoint (death, MI, TVR or stent placement for threatened vessel closure at 30 days) occurred in 11.6% in the placebo group versus 9.1% in the 135/0.5 eptifibatide group (p = 0.035) and 10% in the 135/0.75 eptifibatide group (p = 0.18). The Enhanced Suppression of Platelet IIb/IIIa Receptor with Integrilin Therapy (ESPRIT) trial studied a dose of eptifibatide 3- to 4-fold higher than that used in IMPACT II trial in patients undergoing non-emergent coronary artery stenting (two 180 microg/kg bolus doses 10 minutes apart). The 6-month composite endpoint (death, MI, TVR and 'bailout' eptifibatide use) occurred in 18.3% of patients in the placebo group versus 14.2% in the eptifibatide group (p = 0.008) and was maintained at 12 months (22.1% in the placebo group vs 17.5% in the eptifibatide group, p = 0.0068). The Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy (PURSUIT) study in 10 948 patients was designed to study the effect of eptifibatide in the treatment of acute coronary syndromes (ACS) using two different dosages (180 microg/kg bolus followed by an infusion of either 1.3 microg/kg/min or 2 microg/kg/min. The primary endpoint, a composite of death or MI at 30 days, occurred in 15.7% of placebo-treated patients and 14.2% of eptifibatide-treated patients (p = 0.042). This difference was maintained at 7 days (11.6% in the placebo group vs 10.1% in the eptifibatide group, p = 0.016) and at 30 days (15.7% in the placebo group vs 14.2% in the eptifibatide group). In the eptifibatide studies, the rates of major bleeding were 0.7% (0.5% in the control group) in ESPRIT and 2.1% (1.3% in the placebo group) in PURSUIT. The incidence of intracranial bleeding was 0.2% in ESPRIT (0.1% in the placebo group) and 0.7% in PURSUIT (0.8% in the placebo group). Significant thrombocytopenia (platelet count <20 000/microL) was reported in 0.2% of the patients receiving eptifibatide in the ESPRIT trial (0% in the placebo group) and in <1% in PURSUIT (<1% in the placebo group). In summary, several clinical trials have demonstrated a clear-cut reduction in a variety of ischemic events in patients receiving eptifibatide as adjunctive pharmacotherapy during PCI.

Influence of concurrent renal dysfunction on outcomes of patients with acute coronary syndromes and implications of the use of glycoprotein IIb/IIIa inhibitors

OBJECTIVES

The purpose of this study was to examine the in-hospital outcome and influence of glycoprotein (GP) IIb/IIIa antagonists on patients with acute coronary syndromes (ACS) across a range of renal function.

BACKGROUND

Recent studies demonstrate increasing cardiovascular risk with progressive renal dysfunction. Previous studies investigating GP IIb/IIIa antagonist use have excluded patients with renal dysfunction.

METHODS

Patients presenting with ACS between January 1999 and May 2000 were identified, and data on demographics, in-hospital management, and clinical events were collected using standardized definitions. Patients were stratified according to renal function assessed by calculated creatinine clearance (CrCl) at presentation. Primary outcome measures included in-hospital mortality and major bleeding events.

RESULTS

Renal insufficiency was present in 312 of 889 patients. There were 40 in-hospital deaths. In non-dialysis-dependent patients, as CrCl worsened, there was a decline in utilization of routine diagnostics and therapeutics, an increase in in-hospital mortality (p = 0.002), and an increase in major bleeding (p = 0.03). Although the use of GP IIb/IIIa antagonists was associated with an increase in major bleeding (p < 0.001), there was a protective effect on in-hospital mortality (p = 0.04) after controlling for CrCl.

CONCLUSIONS

Renal dysfunction is present in a substantial proportion of patients with ACS and is associated with increased in-hospital death. Although GP IIb/IIIa antagonist use in patients with ACS and renal insufficiency resulted in increased bleeding events, its administration was associated with a decreased risk of in-hospital mortality. These preliminary findings need to be confirmed in future randomized clinical trials.

Treatment effects of eptifibatide in planned coronary stent implantation in patients with chronic kidney disease (ESPRIT Trial)

The role of platelet glycoprotein IIb/IIIa inhibitor therapy in patients with mild renal impairment is not well characterized. Our objective was to explore the associations of creatinine clearance (CrCl) with outcomes in a trial of eptifibatide therapy in patients who underwent percutaneous coronary intervention (PCI). We analyzed 48-hour and 30-day outcomes of patients enrolled in the Enhanced Suppression of the Platelet IIb/IIIa Receptor with Integrilin Therapy (ESPRIT) trial. Patients were randomly assigned to placebo or eptifibatide as an adjunct to stent implantation (1,755 with CrCl > or =60 ml/min and 289 with CrCl <60 ml/min). CrCl was calculated using the Cockcroft and Gault formula, and the associations of CrCl with outcomes were evaluated using logistic regression models. Patients with CrCl <60 ml/min were more likely to be older, women, hypertensive, and have a history of coronary artery bypass surgery, stroke, or peripheral vascular disease. The interaction of eptifibatide with CrCl had borderline significance for the 30-day outcome (p = 0.109). Treatment effect trended toward a greater magnitude in patients with lower CrCl (60 ml/min) (odds ratio 0.53, confidence interval 0.34 to 0.83) compared with those with higher CrCl (90 ml/min) (odds ratio 0.68, confidence interval 0.49 to 0.94). An accompanying increase in bleeding risk also was not apparent with lower CrCl. The treatment effect of eptifibatide is realized regardless of renal function and trends toward being greater in patients with mild renal impairment.

Bleeding associated with eptifibatide targeting higher risk patients with acute coronary syndromes: incidence and multivariate risk factors

The objective of this study was to determine the safety of the glycoprotein IIb/IIIa receptor inhibitor eptifibatide in patients at high risk for adverse clinical outcomes and to determine risk factors for eptifibatide-associated bleeding. Consecutive patients (n = 175) who presented with an acute coronary syndrome and who were at high risk for adverse clinical outcomes were prospectively observed for eptifibatide-associated bleeding, which was classified according to Thrombolysis in Myocardial Infarction (TIMI) and Global Use of Strategies to Open Occluded arteries (GUSTO) criteria. High risk was defined as unstable angina or non-Q-wave myocardial infarction with at least one of the following: left ventricular ejection fraction < 40%, diabetes mellitus, ST segment depression or transient ST segment elevation, serum [troponin I] > 2.5 ng/mL, and recurrent angina symptoms after initiation of conventional antianginal therapy. Bleeding incidences in the patients in this study were compared with those in the 4722 eptifibatide-treated patients in the Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy (PURSUIT) trial. Compared to PURSUIT patients, the population in this study was similar in age but had a higher proportion of females, African Americans, hypertension, diabetes, prior myocardial infarction, heart failure, and revascularization. Bleeding incidences in this study's patients were similar to or lower than those in the PURSUIT population: TIMI major 1.1% versus 10.8%, TAMI minor 12.6% versus 13.1%, GUSTO severe 1.7% versus 1.5%, GUSTO moderate 3.9% versus 11.3%, and GUSTO mild 19.7% versus 26.1%. Renal dysfunction was an independent risk factor for TIMI (odds ratio = 9.1 ([95% CI= 1.6-52.5]) and GUSTO (odds ratio = 6.1 [95% CI = 1.2-30.0]) bleeding. In conclusion, despite being at higher risk for adverse outcomes, patients administered eptifibatide according to this study's institutional guidelines had comparable or lower bleeding rates than in the PURSUIT trial. Renal dysfunction is an independent risk factor for eptifibatide-induced bleeding.

Antagonists of platelet fibrinogen receptor are less effective in carriers of Pl(A2) polymorphism of beta(3) integrin

The polymorphism Leu(33)-->Pro (platelet-specific antigen; Pl(A1/A2)) of platelet GPIIIa is a potential risk factor for arterial thrombosis. However, its influence on platelet function remains controversial and little is known about its impact on platelet sensitivity to GPIIb-IIIa antagonists. Our objective was to compare the effectiveness of various GPIIb-IIIa antagonists in Pl(A2)(+) and Pl(A2)(-) carriers. Platelet aggregation was monitored in healthy donors including Pl(A2)(-) (N=31) and Pl(A2)(+) subjects (N=27; 23 Pl(A1/A2), 4 Pl(A2)/(A2)) using the impedance and turbidimetric aggregation techniques. We evaluated the inhibition of ADP- and collagen-induced aggregation by disintegrins, kistrin and echistatin, and the low-molecular-weight blockers, GR144053F ((4-[4-[4-(aminoiminomethyl]-1-piperazinyl]-1-piperidineacetic acid, hydrochloride trihydrate) and eptifibatide (N(6)-(aminoiminomethyl)-N(2)-(3-mercapto-1-oxopropyl-L-lysylglycyl-L-alpha-aspartyl-L-tryptophyl-L-propyl-L-cysteinamide, cyclic (1-->6)-disulfide). Kistrin (10-30 nmol/l) inhibited ADP- and collagen-induced aggregation stronger in Pl(A2)(-) donors than in Pl(A2)(+) donors; there was a significant difference between 50% inhibitory concentrations (IC(50)). The same tendency occurred with moderate concentrations of eptifibatide (40-100 nmol/l) and also at low concentrations of GR144053F (5-10 nmol/l) and high concentrations of echistatin (80-150 nmol/l), although in the case of the two latter inhibitors, the estimated IC(50) values were not significantly different. In conclusion, GPIIb-IIIa blockers representing various classes are less effective inhibitors of platelet aggregation in Pl(A2)(+) carriers; however, the effect of the genotype is both agonist- and antagonist-dependent.

Using a peptide inhibitor of the glycoprotein IIb/IIIa platelet receptor: initial experience in patients with acute peripheral arterial occlusions

OBJECTIVE

The purpose of this study was to evaluate the efficacy of eptifibatide, an inhibitor of the glycoprotein (GP) IIb/IIIa platelet receptor, in the thrombolytic treatment of patients with acute peripheral arterial occlusive disease.

MATERIALS AND METHODS

We retrospectively reviewed our experience with the use of a GP IIb/IIIa receptor inhibitor, eptifibatide, during thrombolysis in 17 patients with acute lower extremity arterial occlusions who also received intraarterial recombinant tissue plasminogen activator (rt-PA) and heparin. Four of the 17 patients received their loading dose of eptifibatide by direct intraarterial injection, whereas the remaining 13 received an IV loading dose. We compared their results with those of 11 other patients who received only rt-PA and heparin with respect to success and complication rates, duration of thrombolytic therapy, and total rt-PA dose.

RESULTS

We found no significant difference in successful outcome (p = 1.00), major complications (p = 1.00), duration of therapy (p = 0.21), or total rt-PA dose (p = 0.67) between those who received eptifibatide and those who did not during thrombolytic therapy. However, those patients who received an intraarterial loading dose of eptifibatide required substantially less rt-PA (9.0 +/- 4.4 mg vs 38.9 +/- 30.7 mg) to achieve successful thrombolysis.

CONCLUSION

The adjunctive use of a GP IIb/IIIa platelet receptor inhibitor during thrombolysis for arterial occlusions may decrease the total dose of rt-PA required for thrombolysis without compromising success or complication rates. A prospective randomized study is needed to confirm that inhibitors of the GP IIb/IIIa platelet receptor can facilitate thrombolytic therapy in patients with acute lower extremity arterial occlusions.

Pharmacokinetics and pharmacodynamics of low-molecular-weight heparins and glycoprotein IIb/IIIa receptor antagonists in renal failure

Data regarding the use of low-molecular-weight heparins (LMWHs) and glycoprotein (GP) IIb/IIIa receptor antagonists in patients with renal failure are limited. Renal failure has the potential to increase the risk of adverse drug events associated with LMWHs and GP IIb/IIIa receptor antagonists. This is due to changes in the pharmacokinetic and pharmacodynamic profiles of these agents in patients with renal failure. Until more data are available, clinicians should consider alternative therapies in this patient population.

[The efficacy of platelet IIb/IIIa receptor blockers in acute coronary syndromes]

The knowledge of the central role of platelets in the pathogenesis of acute coronary syndromes, on the one hand, and the fact that aspirin is a weak antiplatelet agent on the other, have led to an intensive investigational activity in antiplatelet drugs in the last years. Actually, the literature in the last two years is inundated with studies on the use of platelet IIb/IIIa receptor blockers in different clinical settings. Agents that block the IIb/IIIa platelet receptor have shown to be useful in improving prognosis of patients with acute coronary syndromes, especially in those undergoing percutaneous coronary revascularization procedures. However, their potential risk of bleeding and their high cost have prevented them from being applied universally and routinely. Furthermore there are still some unclear issues regarding the use of these drugs such as their correct dosage, the optimal duration of treatment and the direct comparison of the efficacy of different types of IIb/IIIa blockers available. On the other hand, oral IIb/IIIa antagonists have not improved the efficacy of aspirin to date and, moreover, they have been proven to be unsafe. Finally, it is necessary to identify those patients who will obtain the greatest benefit from the treatment in order to avoid the unnecessary risks and costs that would be derived from their universal use.