Thrombotic thrombocytopenic purpura associated with clopidogrel

Potentially inappropriate medication use in elderly Japanese patients

BACKGROUND

Modified Beers criteria for elderly Japanese patients were developed in 2008 by consensus among 9 experts to reflect regional clinical practice and available medications in Japan. Since then, many physicians and pharmacists have expressed interest in obtaining more information about the criteria and alternative drug choices.

OBJECTIVE

This study examined the incidence, health care utilization, and costs associated with potentially inappropriate medications (PIMs) in elderly patients based on the modified Beers criteria.

METHODS

A retrospective, observational cohort study was conducted using health insurance claims data in Japan. The study population included elderly patients aged >or=65 years who had at least 2 pharmacy claims in separate months over a 1-year period (April 2006 through March 2007). Use of the PIMs was identified using the modified criteria, and 1-year incidence rates were calculated for the total study population and for subgroups stratified by age and sex. A logistic regression model was used to examine demographic and clinical characteristics associated with PIMs. Health care utilization rates and costs were also analyzed and compared between patients with and without PIMs using generalized linear models. All models included dummy variables indicating age category, female sex, hospitalization, polypharmacy, index month, and number of Elixhauser comorbidities to adjust for potential confounders.

RESULTS

Among 6628 elderly patients, 71.2% (4721/6628) were female and 62.9% (4167/6628) were aged 65 to 74 years; 43.6% (2889/6628) were prescribed at least one PIM. The most commonly used PIMs were histamine-2 blockers (20.5% [1356/6628]), benzodiazepines (11.4% [756/6628]), and anticholinergics and antihistamines (7.9% [526/6628]). No significant differences in incidence rates were observed based on age or sex. Inpatient service use, polypharmacy, and comorbidities of peptic ulcer, depression, and cardiac arrhythmias were significant predictors of PIM use while controlling for other factors. PIM users had significantly higher hospitalization risk (1.68-fold), more outpatient visit days (1.18-fold), and higher medical costs (33% increase) than did nonusers.

CONCLUSIONS

In a group of elderly Japanese patients, 43.6% used at least one PIM over a 1-year period in this study. PIM use was associated with greater health care utilization rates and costs.

[Hemolytic uremic syndrome in adults]

Hemolytic uremic syndrome (HUS) is related to a renal thrombotic microangiopathy, inducing hypertension and acute renal failure (ARF). Its pathogenesis involves an activation/lesion of microvascular endothelial cells, mainly in the renal vasculature, secondary to bacterial toxins, drugs, or autoantibodies. An overactivation of the complement alternate pathway secondary to a heterozygote deficiency of regulatory proteins (factor H, factor I or MCP) or to an activating mutation of factor B or C3 can also result in HUS. Less frequently, renal microthrombi are due to an acquired or a constitutional deficiency in ADAMTS-13, the protease cleaving von Wilebrand factor. Hemolytic anemia with schistocytes, thrombocytopenia without evidence of disseminated intravascular coagulation, and renal failure are consistently found. In typical HUS, a prodromal diarrhea, with blood in the stools, is observed, related to pathogenic enterobacteria, most frequently E. Coli O157:H7. HUS may also occur in the post partum period, and is then related to a factor H or factor I deficiency. HUS may also occur after various treatments such as mitomycin C, gemcitabine, ciclosporin A, or tacrolimus, and as reported more recently bevacizumab, an anti VEGF antibody. Atypical HUS are not associated with diarrhea, may be sporadic or familial, and can be related to an overactivation of the complement alternate pathway. More recently, some of them have been related to a mutation of thrombomodulin, which also regulates the alternate pathway of complement. In adults, several HUS are encountered in the course of chronic nephropathies: nephroangiosclerosis, chronic glomerulonephritis, post irradiation nephropathy, scleroderma, disseminated lupus erythematosus, antiphospholipid syndrome. Overall the prognosis of HUS has improved, with a patient survival greater than 85% at 1 year. Chronic renal failure is observed as a sequella in 20 to 65% of the cases. Plasma infusions and plasma exchanges are effective in most of the cases to treat hemolysis and thrombocytopenia. Steroid therapy is debated, as well as immunosuppressive drugs, including rituximab, in autoimmune forms. A new monoclonal anti-C5 antibody is tested, and seems to be effective in atypical HUS with abnormal complement alternate pathway activation. If terminal renal failure occurs, renal transplantation can be performed but the risk of recurrence, which very low in post infectious forms of HUS, is about 70 to 80% in genetic forms of complement regulatory protein deficiency.

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

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

Profound thrombocytopenia after primary exposure to eptifibatide

Eptifibatide is a glycoprotein IIb/IIIa receptor antagonist used to reduce the incidence of ischemic events in patients with acute coronary syndromes and those undergoing percutaneous coronary intervention. A minority of patients given eptifibatide develop acute, profound thrombocytopenia (<20,000 cells/mm(3)) within a few hours of receiving the drug. This case report discusses a patient who developed profound thrombocytopenia within hours of receiving eptifibatide for the first time. The Naranjo algorithm classified the likelihood that this patient's thrombocytopenia was related to eptifibatide as probable. Profound thrombocytopenia is an uncommon but clinically important complication of eptifibatide. This case report emphasizes the importance of monitoring platelet counts routinely at baseline and within 2-6 hours of eptifibatide administration.

[Implications of the REACH registry for vascular surgery]

Because of the increase in life expectancy, peripheral artery disease (PAD) has become a major health problem. A study performed in Spain in persons aged more than 65 years old found an overall prevalence of PAD of 9.9%. The most important risk factors for PAD were smoking, diabetes mellitus, advanced age, hyperlipidemia and hypertension. Treatment includes smoking cessation, exercise, statins, platelet antiaggregants, cilostazol or hemorheologic agents, and revascularization techniques. Data from the Spanish arm of REACH indicate that the PAD subgroup shows the poorest control of blood pressure and cholesterol and that use of platelet antiaggregants and statins is lowest in these patients, indicating that therapeutic and preventive strategies are not being correctly applied.

Treatment strategies for peripheral artery disease

Peripheral arterial disease is an underecognized manifestation of systemic atherosclerosis associated with high rates of cardiovascular morbidity and mortality. The rationale of therapy is to reduce cardiovascular risk, improve symptoms of intermittent claudication, and prevent the development of critical limb ischemia and amputation. Exercise therapy and several pharmacologic agents have been shown to improve walking distance in patients with intermittent claudication. Patients with lifestyle-interfering symptoms despite exercise, or those who progress to critical limb ischemia, frequently undergo revascularization. Endovascular techniques are commonly used in these patients. Combined pharmacological and endovascular strategies will play an increasing role in management of these patients in the future.

Clinical pharmacology of antithrombotic drugs in coronary artery disease

Coronary heart disease is the leading cause of death in the Western world. Antithrombotic therapy is the cornerstone of its successful treatment. Clinical trials have demonstrated that antithrombotic therapy reduces the risk for recurrent myocardial infarction and cardiovascular death. Antiplatelet drugs and anticoagulants interfere with haemostasis and thus bleeding is a major risk factor of these drugs. The benefit of antithrombotic therapy must therefore be carefully balanced with the risk of bleeding and other potential adverse reactions of these drugs. However, to date there is no firm evidence that dosage adaptation of aspirin or clopidogrel according to platelet aggregation testing translates directly into any clinical benefit. Resistance to antithrombotic drugs is a serious problem because these patients are at a higher risk of myocardial infarction, stroke and cardiovascular death. It has most recently been demonstrated that resistance to clopidogrel is at least in part caused by polymorphism of CYP2C19. Clinical trials have also demonstrated that optimal benefit in different settings depends unequivocally on the meticulous choice of the various drugs. Thus, profound knowledge of the clinical pharmacological profiles of the different antithrombotic drugs is indispensable for successful treatment.

Pharmacology of dimethyl sulfoxide in cardiac and CNS damage

The pharmacological effects of dimethyl sulfoxide (DMSO) administration include some desirable properties that may be useful in the treatment of medical disorders resulting in tissue injury and compromised organ systems. These properties include the reported effects of DMSO on impaired blood flow, suppression of cytotoxicity from excess glutamate release that may result in lethal NMDA-AMPA activation, restriction of cytotoxic Na(+) and Ca(2+) entry into damaged cells, blocking tissue factor (TF) from contributing to thrombosis, reduction of intracranial pressure, tissue edema, and inflammatory reactions, and inhibition of vascular smooth muscle cell migration and proliferation that can lead to atherosclerosis of the coronary, peripheral, and cerebral circulation. A review of the basic and clinical literature on the biological actions of DMSO in cardiac and central nervous system (CNS) damage or dysfunction indicates that this agent, alone or in combination with other synergistic molecules, has been reported to neutralize or attenuate pathological complications that harmed or can further harm these two organ systems. The effects of DMSO make it potentially useful in the treatment of medical disorders involving head and spinal cord injury, stroke, memory dysfunction, and ischemic heart disease.

Molecular basis of ADAMTS13 dysfunction in thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathic disorder characterized by thrombocytopenia, hemolytic anemia, neurological and renal manifestations, and fever. It is associated with dysfunctional von Willebrand factor (VWF) proteolysis and the occurrence of VWF- and platelet-rich thrombi in the microcirculation of multiple organs, including the kidneys. Von Willebrand factor is a large glycoprotein that circulates in plasma as a series of multimers, and it plays a major role in primary hemostasis by inducing the formation of platelet plugs at sites of vascular injury and high-shear stress. Its activity is dependent on the sizes of the multimers, with ultra-large (UL) VWF multimers being biologically very potent. The ULVWF multimers are rapidly degraded upon their secretion from endothelial cells in normal individuals but not in the circulation of TTP patients, causing the formation of disseminated thrombi in the latter. The defective breakdown of VWF is attributed to a severely deficient activity of the VWF-cleaving protease ADAMTS13, a plasma metalloprotease synthesized in the liver, kidneys, and endothelium. This protease rapidly degrades VWF-platelet strings under flow by proteolytic cleavage of the VWF subunit, thereby regulating the size of the platelet thrombus. Congenital TTP occurs due to ADAMTS13 mutations, with the usual debut occurring during the first years of life, while acquired TTP is associated with auto-antibodies against ADAMTS13.

Occurrence, predictors, and outcomes of post-percutaneous coronary intervention thrombocytopenia in an unselected population

OBJECTIVES

We sought to determine the occurrence, predictors, and prognostic impact of post-percutaneous coronary intervention (post-PCI) thrombocytopenia on an unselected real-world patient population.

BACKGROUND

Thrombocytopenia after PCI has been shown to portend worse prognosis in clinical trials. The significance of post-PCI thrombocytopenia has not previously been examined outside the clinical trial setting.

METHODS

The study cohort consisted of 1,302 consecutive patients with normal baseline platelet count (150 x 10(9)/L). Post-PCI thrombocytopenia was defined as nadir platelet count <100 x 10(9)/L or a drop >50% from baseline. The primary outcomes were in-hospital and 6-month rates of death and major adverse cardiovascular events (MACE), and the secondary outcomes were bleeding, need for blood transfusion, and length of hospital stay. Logistic regression was performed to identify independent predictors.

RESULTS

Post-PCI thrombocytopenia developed in 41 patients (occurrence 3.1%). Independent predictors were baseline creatinine clearance (odds ratio [OR] 1.02 for every unit decrease, 95% confidence interval [CI] 1.01-1.03, P=0.001), failed PCI (OR 3.8, CI 1.6-9.4, P=0.003), and use of intraaortic balloon pump (OR 2.8, CI 1.1-6.8, P=0.024). All study outcomes were significantly higher in patients with post-PCI thrombocytopenia. Post-PCI thrombocytopenia independently predicted MACE at 6 months (hazard ratio 2.7, CI 1.3-5.5, P=0.0069) and all the secondary outcomes.

CONCLUSIONS

Post-PCI thrombocytopenia occurred in 3.1% of patients in an unselected real-world population and carried a significant detrimental impact on prognosis. Failed PCI was the strongest correlate identified.

Ticlopidine- and clopidogrel-associated thrombotic thrombocytopenic purpura (TTP): review of clinical, laboratory, epidemiological, and pharmacovigilance findings (1989-2008)

Thrombotic thrombocytopenic purpura (TTP) is a fulminant disease characterized by platelet aggregates, thrombocytopenia, renal insufficiency, neurologic changes, and mechanical injury to erythrocytes. Most idiopathic cases of TTP are characterized by a deficiency of ADAMTS13 (a disintegrin and metalloprotease, with thrombospondin-1-like domains) metalloprotease activity. Ironically, use of anti-platelet agents, the thienopyridine derivates clopidogrel and ticlopidine, is associated with drug induced TTP. Data were abstracted from a systematic review of English-language literature for thienopyridine-associated TTP identified in MEDLINE, EMBASE, the public website of the Food and Drug Administration, and abstracts from national scientific conferences from 1991 to April 2008. Ticlopidine and clopidogrel are the two most common drugs associated with TTP in FDA safety databases. Epidemiological studies identify recent initiation of anti-platelet agents as the most common risk factor associated with risks of developing TTP. Laboratory studies indicate that most cases of thienopyridine-associated TTP involve an antibody to ADAMTS13 metalloprotease, present with severe thrombocytopenia, and respond to therapeutic plasma exchange (TPE); a minority of thienopyridine-associated TTP presents with severe renal insufficiency, involves direct endothelial cell damage, and is less responsive to TPE. The evaluation of this potentially fatal drug toxicity can serve as a template for future efforts to comprehensively characterize other severe adverse drug reactions.

P2Y12 Inhibitors in Cardiovascular Disease: Focus on Prasugrel

OBJECTIVE

To review the literature describing the pharmacology, pharmacokinetic properties, efficacy, and adverse effects of prasugrel, a new thienopyridine.

DATA SOURCES

A literature search was conducted (1966–November 2008) of the MEDLINE, Current Contents, EMBASE, and International Pharmaceutical Abstract databases using the key words prasugrel, CS-747, LY640315, and P2Y12. Bibliographies of identified literature were also reviewed for additional references.

STUDY SELECTION AND DATA EXTRACTION

All reports published in English that evaluated prasugrel (or its chemical synonyms) were reviewed. Abstracts without subsequently published reports were excluded.

DATA SYNTHESIS

Given the high rate of recurrent coronary events despite current antiplatelet therapies, agents with potentially greater efficacy are under investigation. Prasugrel is a novel thienopyridine prodrug that is rapidly metabolized to its active platelet-inhibitory metabolite (R-138727) and exerts antiplatelet activity through antagonism of P2Y12 receptors. Prasugrel is very similar in structure and mechanism of action to clopidogrel, as they both possess a methoxycarbonyl group that provides increased pharmacologic activity and an improved hematologic safety profile when compared with ticlopidine. In addition, when compared with clopidogrel, prasugrel demonstrates greater potency and less interpatient variability in the inhibition of platelet aggregation, less in vitro hyporesponsiveness, and, in patients with acute coronary syndromes, a reduced rate of ischemic events. However, this reduction in ischemic events was accompanied by an increased risk of major and fatal bleeding.

CONCLUSIONS

Prasugrel appears to be a promising antiplatelet agent, with emerging clinical data in direct comparison with clopidogrel supporting its role in reducing recurrent ischemic events. Further studies are needed to evaluate the safety and efficacy of prasugrel across various patient populations and clinical scenarios.

THIS ARTICLE IS APPROVED FOR CONTINUING EDUCATION CREDIT ACPE UNIVERSAL PROGRAM NUMBER

407-000-09-001-H01-P

Pharmacovigilance and reporting oversight in US FDA fast-track process: bisphosphonates and osteonecrosis of the jaw

More than half of all serious adverse reactions are identified 7 or more years after a drug receives approval from the US Food and Drug Administration (FDA). In 2002, 9 months after the intravenous bisphosphonate zoledronic acid received regulatory approval for marketing, the FDA received reports of nine patients with cancer, who were treated with zoledronic acid, who unexpectedly developed osteonecrosis of the jaw. During the next 2 years, three oral surgeons described 104 patients with cancer with osteonecrosis of the jaw in the medical literature and identified intravenous bisphosphonate therapy as being common to the care of these patients. In subspecialty medical, radiology, and dental journals, case reports and case series described clinical features of osteonecrosis of the jaw in patients with cancer who were treated with bisphosphonates. Manufacturer-sponsored epidemiological studies reported the first estimates of the incidence of this toxic effect, ranging from 0.1% to 1.8%. By contrast, independent epidemiological efforts from clinicians and the International Myeloma Foundation reported incidence estimates between 5% and 10%. Between 2003 and 2005, warnings about the risks of bisphosphonate-associated osteonecrosis were disseminated by national regulatory agencies, the manufacturers of bisphosphonates, and the International Myeloma Foundation. From 2006, independent clinical recommendations for diagnosis, prevention, and treatment of this toxic effect have been disseminated by manufacturers, national regulatory authorities, the International Myeloma Foundation, and medical specialty organisations. Furthermore, independent efforts by pharmaceutical manufacturers, dental and medical professionals, a non-profit organisation (the International Myeloma Foundation), patients, and regulatory authorities has led to the rapid identification and dissemination of safety information for this serious adverse reaction. Better coordination of safety-related pharmacovigilance initiatives is now needed.

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.

The primary and secondary prevention of coronary artery disease: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

The following chapter devoted to antithrombotic therapy for chronic coronary artery disease (CAD) is part of the Antithrombotic and Thrombolytic Therapy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Grade 1 recommendations are strong and indicate that the benefits do or do not outweigh risks, burden, and costs. Grade 2 suggests that individual patient values may lead to different choices (for a full understanding of the grading see the "Grades of Recommendation" chapter by Guyatt et al in this supplement, CHEST 2008; 133[suppl]:123S-131S). Among the key recommendations in this chapter are the following: for patients with non-ST-segment elevation (NSTE)-acute coronary syndrome (ACS) we recommend daily oral aspirin (75-100 mg) [Grade 1A]. For patients with an aspirin allergy, we recommend clopidogrel, 75 mg/d (Grade 1A). For patients who have received clopidogrel and are scheduled for coronary bypass surgery, we suggest discontinuing clopidogrel for 5 days prior to the scheduled surgery (Grade 2A). For patients after myocardial infarction, after ACS, and those with stable CAD and patients after percutaneous coronary intervention (PCI), we recommend daily aspirin (75-100 mg) as indefinite therapy (Grade 1A). We recommend clopidogrel in combination with aspirin for patients experiencing ST-segment elevation (STE) and NSTE-ACS (Grade 1A). For patients with contraindications to aspirin, we recommend clopidogrel as monotherapy (Grade 1A). For long-term treatment after PCI in patients who receive antithrombotic agents such as clopidogrel or warfarin, we recommend aspirin (75 to 100 mg/d) [Grade 1B]. For patients who undergo bare metal stent placement, we recommend the combination of aspirin and clopidogrel for at least 4 weeks (Grade 1A). We recommend that patients receiving drug-eluting stents (DES) receive aspirin (325 mg/d for 3 months followed by 75-100 mg/d) and clopidogrel 75 mg/d for a minimum of 12 months (Grade 2B). For primary prevention in patients with moderate risk for a coronary event, we recommend aspirin, 75-100 mg/d, over either no antithrombotic therapy or vitamin K antagonist (Grade 1A).

Myocardial infarction in thrombotic thrombocytopenic purpura: a single-center experience and literature review

BACKGROUND

Several case reports and series have described myocardial infarctions (MIs) in patients hospitalized for thrombotic thrombocytopenic purpura (TTP). The exact magnitude and outcome of this complication are unknown.

METHODS

Electronic medical records for patients admitted to Wake Forest University Baptist Medical Center were examined from 1996 to 2005. Those patients having a diagnosis of TTP during the hospitalization period were included in the analysis. Only patients' initial episodes of TTP were analyzed. Baseline cardiac and TTP risk factors were documented. Outcomes analyzed included MIs, arrhythmias, development of congestive heart failure and death.

RESULTS

Eighty-five patients diagnosed with TTP were identified with 13 (15.3%) having MIs, as defined by an elevation of cardiac enzymes. Median troponin I value was 5.9 ng/mL (range 3.7-8.8 ng/mL). Twelve patients had non-ST segment elevation MIs and one had ST segment elevation. Two of 13 patients who had echocardiographic analysis had documented wall motion abnormalities. There was no difference between non-MI and MI patients in cardiac risk factors, prior cardiac events, history of thromboembolic disease or heart failure. There was no in-hospital mortality difference.

CONCLUSION

MI is an important complication of TTP, identified in 15.3% of patients in our study. Routine cardiovascular evaluation with cardiac enzymes, electrocardiography, and telemetry is warranted in acute TTP patients. Appropriate intervention is yet to be determined.

Future innovations in anti-platelet therapies

Platelets have long been recognized to be of central importance in haemostasis, but their participation in pathological conditions such as thrombosis, atherosclerosis and inflammation is now also well established. The platelet has therefore become a key target in therapies to combat cardiovascular disease. Anti-platelet therapies are used widely, but current approaches lack efficacy in a proportion of patients, and are associated with side effects including problem bleeding. In the last decade, substantial progress has been made in understanding the regulation of platelet function, including the characterization of new ligands, platelet-specific receptors and cell signalling pathways. It is anticipated this progress will impact positively on the future innovations towards more effective and safer anti-platelet agents. In this review, the mechanisms of platelet regulation and current anti-platelet therapies are introduced, and strong, and some more speculative, potential candidate target molecules for future anti-platelet drug development are discussed.

Pathogenesis of thrombotic microangiopathies

Profound thrombocytopenia and microangiopathic hemolytic anemia characterize thrombotic microangiopathy, which includes two major disorders: thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS). TTP has at least three types: congenital or familial, idiopathic, and nonidiopathic. The congenital and idiopathic TTP syndromes are caused primarily by deficiency of ADAMTS13, owing to mutations in the ADAMTS13 gene or autoantibodies that inhibit ADAMTS13 activity. HUS is similar to TTP, but is associated with acute renal failure. Diarrhea-associated HUS accounts for more than 90% of cases and is usually caused by infection with Shiga-toxin-producing Escherichia coli (O157:H7). Diarrhea-negative HUS is associated with complement dysregulation in up to 50% of cases, caused by mutations in complement factor H, membrane cofactor protein, factor I or factor B, or by autoantibodies against factor H. The incomplete penetrance of mutations in either ADAMTS13 or complement regulatory genes suggests that precipitating events or triggers may be required to cause thrombotic microangiopathy in many patients.

Genetic and pharmacological targeting of phosphoinositide 3-kinase-gamma reduces atherosclerosis and favors plaque stability by modulating inflammatory processes

BACKGROUND

The role of inflammation at all stages of the atherosclerotic process has become an active area of investigation, and there is a notable quest for novel and innovative drugs for the treatment of atherosclerosis. The lipid kinase phosphoinositide 3-kinase-gamma (PI3Kgamma) is thought to be a key player in various inflammatory, autoimmune, and allergic processes. These properties and the expression of PI3Kgamma in the cardiovascular system suggest that PI3Kgamma plays a role in atherosclerosis.

METHODS AND RESULTS

Here, we demonstrate that a specific PI3Kgamma inhibitor (AS605240) is effective in murine models of established atherosclerosis. Intraperitoneal administration of AS605240 (10 mg/kg daily) significantly decreased early atherosclerotic lesions in apolipoprotein E-deficient mice and attenuated advanced atherosclerosis in low-density lipoprotein receptor-deficient mice. Furthermore, PI3Kgamma levels were elevated in both human and murine atherosclerotic lesions. Comparison of low-density lipoprotein receptor-deficient mice transplanted with wild-type or PI3Kgamma-deficient bone marrow demonstrated that functional PI3Kgamma in the hematopoietic lineage is required for atherosclerotic progression. Alleviation of atherosclerosis by targeting of PI3Kgamma activity was accompanied by decreased macrophage and T-cell infiltration, as well as increased plaque stabilization.

CONCLUSIONS

These data identify PI3Kgamma as a new target in atherosclerosis with the potential to modulate multiple stages of atherosclerotic lesion formation, such as fatty streak constitution, cellular composition, and final fibrous cap establishment.

Lipophilic modifications to dinucleoside polyphosphates and nucleotides that confer antagonist properties at the platelet P2Y12 receptor

Platelet P2Y12 receptors play a central role in the regulation of platelet function and inhibition of this receptor by treatment with drugs such as clopidogrel results in a reduction of atherothrombotic events. We discovered that modification of natural and synthetic dinucleoside polyphosphates and nucleotides with lipophilic substituents on the ribose and base conferred P2Y12 receptor antagonist properties to these molecules producing potent inhibitors of ADP-mediated platelet aggregation. We describe methods for the preparation of these functionalized dinucleoside polyphosphates and nucleotides and report their associated activities. By analysis of these results and by deconstruction of the necessary structural elements through selected syntheses, we prepared a series of highly functionalized nucleotides, resulting in the selection of an adenosine monophosphate derivative (62) for further clinical development.

Antiplatelet therapy in patients undergoing coronary stent implantation: Italian Society of Interventional Cardiology consensus document

The Italian Society of Interventional Cardiology is aware of the existence of significant local and individual disparities and discordant prescriptions in antiplatelet therapy administered with coronary stents, a critical issue due to the large use of drug-eluting stents (DES), the increasing complexity of percutaneous coronary interventions and the more stringent requirement to avoid stent thrombosis. Current percutaneous coronary intervention is attempting more aggressively to treat difficult lesions and patient cohorts with a high procedural success rate. Double antiplatelet therapy with aspirin (ASA) and thienopyridine is the best current treatment to reduce the risk of coronary stent thrombosis. Due to the lower incidence of side-effects compared to ticlopidine, clopidogrel should be the thienopyridine of choice in association with ASA in the double antiplatelet regimen. However, the combination of delayed healing with DES and the increasing complexity of the stent implantation raises more demanding safety concerns about the dosage and duration of dual antiplatelet therapy.

Thrombocytopenia associated with antithrombotic therapy in patients with cardiovascular diseases: diagnosis and treatment

Agents with antiplatelet and anticoagulant activity have been proved to be effective in reducing the incidence of complications following acute coronary syndrome, percutaneous coronary intervention, and cardiopulmonary bypass. However, these agents, including heparin, glycoprotein IIb/IIIa receptor inhibitors, and thienopyridines, are associated with increased risk of bleeding and thrombocytopenia and have been administered together with increasing frequency in a variety of cardiovascular settings. Therefore, clinicians must be familiar with the safety and rational use of these potent antithrombotic agents. Clinical features of thrombocytopenia range from bleeding to thrombosis, even death, and therapy is very different depending on the underlying cause. Additionally, patients may sometimes need urgent intervention or surgery. Thus, it is essential to quickly discriminate the etiology and start appropriate therapy. This review highlights the pathogenesis, clinical and laboratory manifestation, differential diagnosis, and treatment of antithrombotic drug-induced thrombocytopenia in cardiovascular diseases.

Two mechanistic pathways for thienopyridine-associated thrombotic thrombocytopenic purpura: a report from the SERF-TTP Research Group and the RADAR Project

OBJECTIVES

We sought to describe clinical and laboratory findings for a large cohort of patients with thienopyridine-associated thrombotic thrombocytopenic purpura (TTP).

BACKGROUND

The thienopyridine derivatives, ticlopidine and clopidogrel, are the 2 most common drugs associated with TTP in databases maintained by the U.S. Food and Drug Administration (FDA).

METHODS

Clinical reports of TTP associated with clopidogrel and ticlopidine were identified from medical records, published case reports, and FDA case reports (n = 128). Duration of thienopyridine exposure, clinical and laboratory findings, and survival were recorded. ADAMTS13 activity (n = 39) and inhibitor (n = 30) were measured for a subset of individuals.

RESULTS

Compared with clopidogrel-associated TTP cases (n = 35), ticlopidine-associated TTP cases (n = 93) were more likely to have received more than 2 weeks of drug (90% vs. 26%), to be severely thrombocytopenic (84% vs. 60%), and to have normal renal function (72% vs. 45%) (p < 0.01 for each). Compared with TTP patients with ADAMTS13 activity >15% (n = 13), TTP patients with severely deficient ADAMTS13 activity (n = 26) were more likely to have received ticlopidine (92.3% vs. 46.2%, p < 0.003). Among patients who developed TTP >2 weeks after thienopyridine, therapeutic plasma exchange (TPE) increased likelihood of survival (84% vs. 38%, p < 0.05). Among patients who developed TTP within 2 weeks of starting thienopyridines, survival was 77% with TPE and 78% without.

CONCLUSIONS

Thrombotic thrombocytopenic purpura is a rare complication of thienopyridine treatment. This drug toxicity appears to occur by 2 different mechanistic pathways, characterized primarily by time of onset before versus after 2 weeks of thienopyridine administration. If TTP occurs after 2 weeks of ticlopidine or clopidogrel therapy, therapeutic plasma exchange must be promptly instituted to enhance likelihood of survival.

Thrombotic Thrombocytopenic Purpura in Humans and Mice

Thrombotic thrombocytopenic purpura (TTP) is a disorder of blood coagulation that presents classically with the pentad of fever, thrombocytopenia, microangiopathic hemolytic anemia, renal dysfunction and mental status changes. However, the clinical presentation can be quite variable making the diagnosis difficult in many cases. “Hyaline” microthrombi composed primarily of platelets and Von Willebrand Factor (VWF) are found in the small vessels of affected organs and represent the pathological hallmark of the disease. The accompanying tissue ischemia is thought to explain the clinical TTP signs and symptoms. Pathogenesis of TTP has been linked to dysfunction of ADAMTS13, a metalloprotease whose only known substrate is VWF. Interestingly, further investigation into the natural history of TTP has demonstrated that ADAMTS13 deficiency likely is necessary, but not sufficient for the development of this disease, suggesting that additional genetic and/or environmental factors are required for TTP pathogenesis. Recently, a mouse model of TTP was established that recapitulates many of the key clinical features of this disease, including the requirement for further genetic and environmental factors in addition to ADAMTS13 deficiency. Therefore, in addition to being useful for the direct study of disease pathophysiology in vivo , this mouse model may also play a key role in elucidating some of the important environmental and genetic contributors to disease pathogenesis. Here we will review TTP in humans, and then discuss recent information gained from the analysis of ADAMTS13-deficient mice.

Myocardial injury in thrombotic thrombocytopenic purpura: a frequent, perplexing complication

BACKGROUND

Although thrombotic thrombocytopenic purpura (TTP) typically involves the heart, angina and myocardial injury are uncommonly reported; fatal cardiogenic shock is exceptional.

METHODS

We analyzed 26 patients with TTP who had objective evidence of myocardial injury.

RESULTS

Myocardial injury was evident in 6 patients. None had coronary disease. Mean age was 43.6 years; four patients (66%) were female. Mean troponin, creatinine and hemoglobin levels were 7.82 ng/dL (<or=2.1); 2.63 mg/dL and 7.1 g/dL, respectively. Three patients (50%) expired during the index hospitalization; one as a consequence of massive ST-segment elevation myocardial infarction.

CONCLUSIONS

Myocardial injury frequently complicates the TTP syndrome and associated mortality is substantial. In survivors, enduring left ventricular failure is plausible. Widely accepted therapies for myocardial ischemia are not consistently efficacious in the setting of TTP.

Thrombotic thrombocytopenic purpura: a thrombotic disorder caused by ADAMTS13 deficiency

A serious disorder with characteristic microvascular thrombosis involving the brain and other organs, thrombotic thrombocytopenic purpura (TTP) typically presents with thrombocytopenia, hemolysis with schistocytes on blood smears, and mental changes or seizures. It may progress rapidly to a fatal end if the patient is not treated immediately with plasma. Recent advances have shown that TTP is caused by deficiency of a circulating, von Willebrand factor cleaving metalloprotease, ADAMTS13. This new knowledge will provide clues to improve the diagnosis and management of this intriguing disease.

Pharmacological interventions for peripheral artery disease

Peripheral arterial disease (PAD) encompasses the vascular diseases caused primarily by atherosclerosis and thromboembolic pathophysiological processes that alter the normal structure and function of the aorta, its visceral arterial branches and the arteries of the upper and lower extremities. PAD is associated with an increased risk for cardiovascular morbidity and mortality. The goals for pharmacological therapy in PAD should focus on reducing cardiovascular risk, improving walking distance and preventing critical limb ischaemia. Exercise training plays a key role in the therapeutic assessment, as well stopping smoking. Antiplatelet therapy (aspirin) should be given to every PAD patient if there are no contraindications. Neither their combination nor anticoagulant therapy has shown additional benefit in PAD patients. Several pharmacological agents have been developed to improve the functional state of the claudicant and to relieve the symptoms. Many studied drugs have shown either no, a small or a potential benefit. With future development of new drugs for PAD, there is an absolute need for very strict well-designed protocols in order to evaluate the claudication distance, the progression of the disease and the reduction in cardiovascular morbidity and mortality. New developments should focus on improvement of endothelial function, vascular repair and enhancement of collateral circulation.

Thrombotic thrombocytopenic purpura induced by trimethoprim-sulfamethoxazole in a Jehovah's Witness

We report a case of Thrombotic Thrombocytopenic Purpura occurring as an allergic response to trimethoprim-sulfamethoxazole therapy (Bactrim, Septra) in a Jehovah's Witness patient. The patient presented with fulminant microangiopathic hemolytic anemia and thrombocytopenia within 48 hr of initiating therapy with trimethoprim-sulfamethoxazole. Other symptoms of drug hypersensitivity included nausea, vomiting, urticarial rash, and leukopenia. Because of her religious faith, the patient was supported without plasma therapy with use of intravenous immunoglobulin, steroids, rituximab, and erythropoietin.

Noncardiogenic pulmonary edema associated with clopidogrel: a serious but unexpected side effect of clopidogrel

Clopidogrel has a favourable side effect profile, in which the most serious complications are related to bleeding diathesis. Drug reactions represent frequently encountered clinical problems that can also be life-threatening. In the present case, serious noncardiogenic pulmonary edema was observed as an idiosyncratic reaction after clopidogrel use. Using the Naranjo adverse drug reactions probability scale, a possible likelihood of this putative interaction between clopidogrel and pulmonary edema was calculated. Such an adverse effect of clopidogrel has never been reported before. The present report shows the importance of recognizing rare adverse reactions of newer drugs, such as clopidogrel, in clinical practice.

Multiple hemorrhagic strokes from DIC associated with occult large cell carcinoma

BACKGROUND AND PURPOSE

Multiple hemorrhagic strokes are a rare presentation of paraneoplastic disseminated intravascular coagulation (DIC). We present a case of DIC occurring in a patient with occult large cell carcinoma.

SUMMARY OF CASE

A 77-year old Asian-American man presented with 1 month of vision disturbance followed by acute onset of left hemiparesis and encephalopathy. He was found to have three strokes of varying ages, and was placed on aspirin and clopidogrel. He returned 4 days later with hemorrhagic conversion of the strokes and laboratory abnormalities suggestive of DIC. Over the hospital course, he suffered recurrent ischemic strokes and intracerebral hemorrhages despite management of his coagulopathy. On autopsy, an occult large cell carcinoma was found in the hilar lymph nodes, as well as multiple intravascular thrombi.

CONCLUSIONS

Recurrent hemorrhagic strokes associated with DIC may be the initial presentation of occult malignancy. Although adenocarcinoma is classically associated with paraneoplastic DIC, this case demonstrates that large cell carcinoma may also be implicated.

Non-bleeding side effects of clopidogrel: Have large multi-center clinical trials underestimated their incidence?

Large multi-center clinical trials have indicated significant clinical benefits for patients with atherosclerotic vascular diseases receiving clopidogrel therapy. Clopidogrel efficacy has been proven in cardiac and extracardiac vascular diseases. Thus, the popularity of using clopidogrel is likely to increase in the near future. However, clopidogrel therapy may be accompanied by rare life-threatening adverse events. An increasing body of evidence show that clopidogrel is associated with aplastic anemia, thrombocytopenia and neutropenia. Interestingly, the majority of multi-center clinical trials have reported bleeding as the major side effect of clopidogrel therapy and failed to detect the actual incidence of other serious hematological side effects. Highlighting the potential adverse events of clopidogrel therapy in large clinical trials is therefore essential if we are to learn any lessons from having ignored the reporting of serious adverse side effects of a closely related drug (ticlopidine) in its large clinical trials.

Hematologic adverse effects of clopidogrel

Clopidogrel is used as a frontline antiplatelet agent in patients with coronary artery disease, cerebrovascular disease, and peripheral vascular disease. Hematologic complications and bleeding have been the most feared outcome of antithrombotic and antiplatelet agents. Among the thienopyridines, clopidogrel is considered to be a safer alternative to ticlopidine due to its decreased incidence of hematologic adverse effects. Although thrombotic thrombocytopenia purpura is the most reported hematologic adverse effect of clopidogrel; neutropenia, acquired hemophilia, isolated thrombocytopenia or idiopathic immune thrombocytopenia, and thrombotic thrombocytopenia purpura with hemolytic uremic syndrome are other rare yet recognized hematologic adverse effects of clopidogrel. Patients treated with clopidogrel should be carefully monitored for hematologic adverse effects especially in the first 2 to 3 months after initiation of therapy. Early recognition and prompt initiation of treatment can be life saving in patients who have hematologic adverse effects to clopidogrel. We have drafted this review by performing literature search using Medline, Pubmed, and EMBASE search engine with relevant search words for all reported hematologic adverse effects and manifestations of clopidogrel and their management.