Thrombotic thrombocytopenic purpura associated with clopidogrel

Clopidogrel’s role in the management of atherosclerotic disease: a focus on acute coronary syndromes

Recent advances in our understanding of the role of the platelet in the atherosclerotic process beyond the acute formation of arterial blood clots, such as inflammation, have highlighted the role of antiplatelet agents as being much more than just 'blood thinners.' Some of the most important cardiovascular trials performed in the last 20 years have studied antiplatelet therapies. However, despite their long history, current global health implications and proven benefit, there remain substantial gaps in our understanding as to how to best utilize the limited number of antiplatelet agents available. This article will discuss the mechanism of action of the antiplatelet class known as thienopyridines, the pharmacodynamics and pharmacokinetics of the thienopyridine agent clopidogrel (Plavix, Bristol-Myers Squibb and Sanofi Pharmaceuticals) as well as the literature supporting its clinical benefits and areas of ongoing research that will help clarify the optimal utilization of clopidogrel for the treatment of cardiovascular disease.

Overweight individuals are at increased risk for thrombotic thrombocytopenic purpura

Our understanding of the pathophysiology of thrombotic thrombocytopenic purpura, TTP, has increased dramatically in the past few years with the identification of the role of ADAMTS13. Nonetheless, risk factors for the development of acute TTP are few. Informally, obesity was felt to be common in patients with TTP and so a formal study was undertaken to further define this association. We report our data in 105 patients with classical TTP as defined by thrombocytopenia and microangiopathic hemolytic anemia. We found that marked obesity is a previously unrecognized risk factor with an associated odds ratio of 7.6. Interestingly, despite this increased risk, obesity might well be associated with lower mortality, although this did not reach statistical significance.

Thrombotic thrombocytopenic purpura after cephalosporin administration: a possible relationship

BACKGROUND

Acquired thrombotic thrombocytopenic purpura (TTP) is an autoimmune disorder. The pathogenesis is believed to be mediated by an autoantibody directed against the metalloproteinase responsible for the degradation of the very-high-molecular-weight multimers of the vWF. The syndrome can be precipitated by a variety of conditions, and certain medications also have been implicated.

CASE REPORTS

The cases of two patients who took a cephalosporin antibiotic, cephalexin (Keflex, Eli Lilly), and then developed TTP are reported. One patient subsequently received a third-generation cephalosporin, ceftriaxone (Rocephin, Roche), without adverse reaction. Of interest, one patient had taken cefaclor (Ceclor, Eli Lilly) 8 years before and had also developed TTP at that time. The other patient also took cefaclor for approximately 3 weeks before taking cephalexin. In addition, she had had a dose of clarithromycin (Biaxin, Abbott Laboratories) the day before the onset of the TTP symptoms.

CONCLUSIONS

To our knowledge, TTP has not been reported previously after administration of cephalosporin antibiotics. Attention is called to the possibility that this syndrome may occur after exposure to some of these drugs, although the incidence is very rare or, alternatively, underdiagnosed.

Scientific and therapeutic insights into the role of the platelet P2Y12 receptor in thrombosis

Platelets are important mediators of thrombosis in both healthy and diseased vessels. When platelets become activated by various soluble agonists or by adhesion to subendothelium under high shear, they release adenosine-5'-diphosphate that acts in a positive feedback mechanism on two different G-protein coupled receptors (P2Y(12), P2Y(1)) on platelets. This released adenosine-5'-diphosphate, acting through P2Y(12), is critical for sustained aggregation and stabilization of thrombi. P2Y(12) is the target of antithrombotic drugs (ticlopidine, clopidogrel), whereas the role of P2Y(1) in thrombosis remains to be fully established. Recent studies using either inhibitors of key components of signaling pathways or genetically engineered mice have contributed to our understanding of the signaling mechanisms in platelets mediated by adenosine-5'-diphosphate through the P2Y(12) receptor. Studies of patients with defective adenosine-5'-diphosphate mediated aggregation, as well as P2Y(12)-null mice, have revealed the importance of this receptor in mediating platelet activation and aggregation. Recent clinical trials using approved P2Y(12) blockers have extended the use of these drugs to additional patient populations. Recent data demonstrating the role of P2Y(12) in mediating platelet adhesion to thrombogenic surfaces (collagen, von Willebrand factor) provide further rationale as to the clinical efficacy of P2Y(12) blockers. P2Y(12) antagonists in combination with anticoagulants (thrombin inhibitors, factor Xa inhibitors) act synergistically in inhibiting thrombus formation (similar to aspirin) ex vivo. These findings suggest the potential for combination therapies (P2Y(12) antagonists with inhibitors of GPIIb-IIIa, thrombin or Factor Xa, etc.) to provide additional clinical benefit to patients with various cardiovascular diseases, especially those who may be aspirin-resistant.

Platelets: thrombotic thrombocytopenic purpura

Abnormalities of plasma von Willebrand factor (VWF) have been recognized to be associated with thrombotic thrombocytopenic purpura (TTP) for over 20 years. Patients with chronic, relapsing TTP have VWF multimers that are larger than normal, similar in size to those secreted by cultured endothelial cells. Recent observations have documented that a deficiency of a VWF-cleaving protease (termed ADAMTS13) may be responsible for the presence of these unusually large VWF multimers. Multiple mutations of the ADAMTS13 gene can result in ADAMTS13 deficiency and cause congenital TTP; autoantibodies neutralizing ADAMTS13 protease activity have been associated with acquired TTP. In Section I, Dr. Evan Sadler reviews the structure, biosynthesis, and function of the ADAMTS13 protease. He describes the mutations that have been identified in congenital TTP and describes the relationship of ADAMTS13 deficiency to the development of both congenital and acquired TTP. Dr. Sadler postulates that the development of TTP may be favored by conditions that combine increased VWF secretion, such as during the later stages of pregnancy, and decreased ADAMTS13 activity. In Section II, Dr. Bernhard Lämmle describes the assay methods for determining ADAMTS13 activity. Understanding the complexity of these methods is essential for understanding the difficulty of assay performance and the interpretation of assay data. Dr. Lämmle describes his extensive experience measuring ADAMTS13 activity in patients with TTP as well as patients with acute thrombocytopenia and severe illnesses not diagnosed as TTP. His data suggest that a severe deficiency of ADAMTS13 activity (< 5%) is a specific feature of TTP. However, he emphasizes that, although severe ADAMTS13 deficiency may be specific for TTP, it may not be sensitive enough to identify all patients who may be appropriately diagnosed as TTP and who may respond to plasma exchange treatment. In Section III, Dr. James George describes the evaluation and management of patients with clinically suspected TTP, as well as adults who may be described as having hemolytic-uremic syndrome (HUS). Dr. George presents a classification of TTP and HUS in children and adults. Appropriate evaluation and management are related to the clinical setting in which the diagnosis is considered. A clinical approach is described for patients in whom the diagnosis of TTP or HUS is considered (1) following bone marrow transplantation, (2) during pregnancy or the postpartum period, (3) in association with drugs which may cause TTP either by an acute immune-mediated toxicity or a dose-related toxicity, (4) following a prodrome of bloody diarrhea, (5) in patients with autoimmune disorders, and (6) in patients with no apparent associated condition who may be considered to have idiopathic TTP. Patients with idiopathic TTP appear to have the greatest frequency of ADAMTS13 deficiency and appear to be at greatest risk for a prolonged clinical course and subsequent relapse. Management with plasma exchange has a high risk of complications. Indications for additional immunosuppressive therapy are described.

ADAMTS13 activity in thrombotic thrombocytopenic purpura-hemolytic uremic syndrome: relation to presenting features and clinical outcomes in a prospective cohort of 142 patients

Initial management of patients with thrombotic thrombocytopenic purpura-hemolytic uremic syndrome (TTP-HUS) is difficult because of lack of specific diagnostic criteria, high mortality without plasma exchange treatment, and risks of plasma exchange. Although severe ADAMTS13 (a disintegrin-like and metalloprotease with thrombospondin type 1 repeats) deficiency may be specific for TTP, the role of ADAMTS13 activity measurements for initial management decisions is unknown. ADAMTS13 was measured before beginning plasma exchange treatment in 142 (88%) of 161 consecutive patients with clinically diagnosed TTP-HUS with assignment to 1 of 4 categories: less than 5% (severe deficiency), 5% to 9%, 10% to 25%, and more than 25%. Eighteen (13%) of 142 patients had severe ADAMTS13 deficiency. Among 6 predefined clinical categories (stem cell transplantation, pregnant/postpartum, drug association, bloody diarrhea, additional/alternative disorder, idiopathic), severe deficiency occurred only among pregnant/postpartum (2 of 10) and idiopathic (16 of 48) patients. The presenting features and clinical outcomes of the 16 patients with idiopathic TTP-HUS who had severe ADAMTS13 deficiency were variable and not distinct from the 32 patients with idiopathic TTPHUS who did not have severe ADAMTS13 deficiency. Many patients in all ADAMTS13 activity categories apparently responded to plasma exchange treatment. Therefore, severe ADAMTS13 deficiency does not detect all patients who may be appropriately diagnosed with TTP-HUS and who may respond to plasma exchange treatment.

The platelet in diabetes: focus on prevention of ischemic events

Accelerated atherosclerosis and the increased risk of thrombotic vascular events in diabetes may result from dyslipidemia, endothelial dysfunction, platelet hyperreactivity, an impaired fibrinolytic balance, and abnormal blood flow. There is also a correlation between hyperglycemia and cardiovascular (CV) events. The importance of platelets in the atherothrombotic process has led to investigation of using antiplatelet agents to reduce CV risk. A meta-analysis conducted by the Antiplatelet Trialists' Collaboration demonstrated that aspirin reduced the risk of ischemic vascular events as a secondary prevention strategy in numerous high-risk groups, including patients with diabetes. Based on results from placebo-controlled randomized trials, the American Diabetes Association recommends low-dose enteric-coated aspirin as a primary prevention strategy for people with diabetes at high risk for CV events. Clopidogrel is recommended if aspirin allergy is present. There is occasionally a need for an alternative to aspirin or for additive antiplatelet therapy. Aspirin in low doses inhibits thromboxane production by platelets but has little to no effect on other sites of platelet reactivity. Agents such as ticlopidine and clopidogrel inhibit ADP-induced platelet activation, whereas the platelet glycoprotein (Gp) IIb/IIIa complex receptor antagonists block activity at the fibrinogen binding site on the platelet. These agents appear to be useful in acute coronary syndromes (ACSs) in diabetic and nondiabetic patients. A combination of clopidogrel plus aspirin was more effective than placebo plus standard therapy (including aspirin) in reducing a composite CV outcome in patients with unstable angina and non-ST segment elevation myocardial infarction. In a meta-analysis of six trials in diabetic patients with ACSs, intravenous GpIIb-IIIa inhibitors reduced 30-day mortality when compared with control subjects. Results from controlled prospective clinical trials justify the use of enteric-coated low-dose aspirin (81-325 mg) as a primary or secondary prevention strategy in adult diabetic individuals (aged >30 years) at high risk for CV events. Recent studies support the use of clopidogrel in addition to standard therapy, as well as the use of GpIIb-IIIa inhibitors in ACS patients.

Transient ischaemic attacks : new approaches to management

The fact that transient ischaemic attacks are a harbinger for the possible development of ischaemic stroke has been recognised for several decades. However, within the past decade, our concepts regarding transient ischaemic attacks as a distinct entity from stroke and the prognosis for transient ischaemic attack patients have been challenged. In addition, clinical trials have clarified that modern transient ischaemic attack management is more complex than in the past, with the addition of newer pharmacological options to the stroke prevention armamentarium. Recent information regarding newer antiplatelet agents is reviewed in this article, along with results of clinical trials pertaining to warfarin in stroke prevention. The evolving role of statins, ACE inhibitors and estrogen replacement is reviewed. Finally, the appropriate use of surgery following transient ischaemic attacks is outlined. Recent studies have shown that many patients will benefit from a multimodal pharmacological approach following transient cerebral ischaemia, and the potential for combination therapy is highlighted.

Antiplatelet drugs

Antiplatelet drugs protect against myocardial infarction, stroke, cardiovascular death and other serious vascular events in patients with a history of previous vascular events or known risk factors for cardiovascular disease. Aspirin reduces the risk of serious vascular events in patients at high risk of such an event by about a quarter and is recommended as the first-line antiplatelet drug. Clopidogrel reduces the risk of serious vascular events among high-risk patients by about 10% compared with aspirin. It is as safe as aspirin, but much more expensive. It is an appropriate alternative to aspirin for long-term secondary prevention in patients who cannot tolerate aspirin, have experienced a recurrent vascular event while taking aspirin, or are at very high risk of a vascular event (>/= 20% per year). Addition of clopidogrel to aspirin reduces the risk of serious vascular events among patients with non-ST-segment elevation acute coronary syndromes by 20%, and patients undergoing percutaneous coronary intervention by 30%, compared with aspirin alone. Addition of a glycoprotein IIb/IIIa receptor antagonist to aspirin reduces the risk of vascular events among patients with non-ST-segment elevation acute coronary syndromes by 10% and among patients undergoing percutaneous coronary intervention by 30%, compared with aspirin alone; it appears to provide incremental benefit in patients also treated with clopidogrel. Addition of dipyridamole to aspirin seems to be more effective than aspirin alone for preventing recurrent stroke, but its overall effect in preventing serious vascular events in patients with ischaemic stroke and transient ischaemic attack has not been determined.

The case for early detection and integrated intervention in patients with peripheral arterial disease and intermittent claudication

Peripheral arterial disease (PAD) is defined as atherosclerotic disease of the aorta and arteries of the lower extremities. The most frequent manifestations of ischemia occur in the lower extremity arteries, with intermittent claudication as the most common symptom. Intermittent claudication, which is characterized by temporary pain brought on by muscle exertion, is usually experienced in the calf muscles and typically subsides with rest. The atherosclerotic nature of PAD/intermittent claudication makes it an important predictor of risk for cardio- and cerebrovascular disease, as well as limb loss. Thus, active screening and early diagnosis of PAD/intermittent claudication, in addition to aggressive management that incorporates risk factor modification, exercise therapy, platelet inhibition and other appropriate pharmacotherapy, and potential lifestyle changes, play important roles in overall patient management. Pharmacotherapy with cilostazol has been shown to improve maximal and pain-free walking distances. Uncontrolled and severely debilitating intermittent claudication may require revascularization.

Therapeutic hemapheresis practitioners need to know about the treatment of thrombotic thrombocytopenic purpura

In the field of therapeutic apheresis, thrombotic thrombocytopenic purpura (TTP) makes up a large percentage of the conditions treated by plasma exchange. The implementation of plasma exchange in the treatment of TTP has been shown to reduce the mortality rate for this group of patients significantly. Apheresis operators see many patients with acute symptoms, the "chronic" syndrome of TTP, and those with a "relapsing" TTP. The apheresis practitioner is with the patient for several hours during each treatment, and thus becomes an element of continuity in the care and assessment of the TTP patient. Progress in understanding the pathophysiology of this condition necessitates the frequent review of literature published regarding TTP, and continuing education of staff and physicians.

[Clopidogrel and thrombopenia. A case report]

We report our experience with a case of isolated profound thrombocytopenia after clopidogrel (thienopyridine) administration. No adverse event such as bleeding or thrombotic event had occurred, although clopidogrel has been discontinued two weeks after the coronary artery stenting. Despite the safety of clopidogrel, this case demonstrates that clopidogrel can be associated not only with thrombotic thrombocytopenic purpura but also with isolated thrombocytopenia.

Clopidogrel-induced systemic inflammatory response syndrome

Clopidogrel bisulfate, a widely used inhibitor of platelet aggregation, is considered at least as safe as aspirin. We describe a patient who developed a systemic inflammatory response syndrome consisting of high fever, tachycardia, cellulitis-like rash, impaired liver function, and mild leukopenia after receiving clopidogrel before coronary angiography and stent implantation. The reaction resolved promptly after withdrawal of the drug and recurred shortly after a rechallenge dose was administered, thus making the diagnosis of a clopidogrel-induced reaction highly probable. Recognition of this clopidogrel-induced syndrome is extremely important, both for rapid discontinuation of the offending drug and for avoidance of unnecessary drug therapy or invasive procedures.

Drug therapy of neurovascular disease

Recent advances in the prevention and pharmacotherapy of cerebrovascular disease have provided more favorable clinical outcomes. For the treatment of an acute ischemic stroke, the early use of thrombolytic agents can reduce the degree of brain damage while improving functional outcomes. However, trials evaluating various classes of other neuroprotective agents have not shown benefit to date. For the prevention of second stroke, the use of antiplatelet drugs, HMG-CoA reductase inhibitors, and angiotensin-converting enzyme inhibitors with a diuretic have shown benefit in reducing new events. In patients with underlying heart disease or atrial fibrillation, warfarin appears to be the drug of choice in preventing stroke. Early treatment of hemorrhagic stroke with calcium channel blockers can improve the functional outcome. Innovative therapies are now available for the treatment of migraine and vascular dementia. Primary prevention of stroke remains the optimal therapeutic strategy and includes treatment of systemic hypertension and hypercholesterolemia.

Thrombotic thrombocytopenic purpura (TTP) presenting as pancreatitis

Thrombotic thrombocytopenic purpura (TTP) is a rare clinical entity. It is a multi-systemic disorder characterized by a clinical pentad of thrombocytopenia, microangiopathic hemolytic anemia, diffuse and nonfocal neurologic symptoms, decreased renal function, and fever. Abdominal pain is an uncommon presenting symptom for TTP. Pancreatitis may occur from TTP or, in a few cases, may trigger TTP. The clinical diagnosis of TTP is generally difficult because there are many varied clinical presentations and the full expression of the pentad may be prolonged. However, once the diagnosis is suspected or confirmed, immediate plasmapherseis with plasma exchange must be performed to reduce the severe morbidity from neurologic disability.

Antiplatelet prescribing patterns for TIA and ischemic stroke: the Indiana University experience

OBJECTIVE

To evaluate antiplatelet prescribing patterns by Indiana University Hospital (IU) neurologists, determine what drives antiplatelet agent decisions, and determine changes made with recurrent cerebrovascular events despite proven antiplatelet therapy. There are now four approved therapies for secondary prevention of cerebrovascular events. As these agents exhibit their effects through different pathways, physicians must choose antiplatelet agents based on other factors.

DESIGN

We retrospectively reviewed charts of neurology patients diagnosed with non-fatal ischemic stroke or TIA at IU from January 1, 1997 to August 31, 2001. Patients were excluded if: discharge diagnosis was not non-fatal ischemic stroke or TIA, they were enrolled in clinical trials, or were placed on anticoagulation therapy with warfarin. Patients' antiplatelet agents at discharge were reviewed to determine if specific factors led to the choice of antiplatelet agent.

RESULTS

A total of 177 patients experienced non-fatal ischemic strokes or TIAs. Of these, 74 were not on prior antiplatelet therapy and 103 were on antiplatelet agents prior to admission. For patients not on therapy, aspirin was the most commonly prescribed agent, with a trend for low-dose aspirin. For patients already on an antiplatelet agent, typically the dose of aspirin was increased or combination therapy initiated.

CONCLUSION

Our experience supports the use of aspirin as a first-line agent for secondary prevention in cerebrovascular disease. For antiplatelet-nai;ve patients, low-dose aspirin is the most frequently used agent. For patients previously on antiplatelet agents, aspirin dosage is increased or clopidogrel is added. High-dose aspirin and ticlopidine use is no longer favored.

Current concepts in the diagnosis and management of thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura is a multisystem disease characterized by thrombocytopenia, hemolytic anemia, renal failure, fever, and neurologic abnormalities. Plasma exchange has revolutionized the outcome of this entity from a once fatal disease to a disease that potentially is cured or has prolonged remission. The understanding of the pathophysiology of TTP continues to evolve. Recently, investigators showed that a deficiency in a specific plasma protease responsible for cleaving vWf plays a crucial role in the familial form of TTP. This explains in part why patients usually respond to plasma exchange therapy. The identification of a mutation in a specific gene that belongs to the metalloproteinase family located at chromosome 9q34 could have important therapeutic implications. TTP can be induced by certain drugs, especially immunosuppressants, in the setting of bone marrow and solid organ transplantation. This disease also has been described in association with HIV, pregnancy, cancer, and chemotherapy. TTP remains an ideal example of how knowledge about the etiology of a disease can improve therapeutic interventions.

Treatment of peripheral arterial disease

Peripheral arterial disease (PAD) is a manifestation of systemic atherosclerosis strongly associated with cardiovascular (CV) morbidity and mortality. Approximately 12% of the US adult population is affected. Despite its prevalence, the disease has received little attention from clinicians. The primary causes of death in patients with PAD are myocardial infarction and stroke; thus, current treatment strategies for symptomatic PAD include aggressive modification of risk factors for CV disease such as cessation of smoking, treatment of hypertension and diabetes, and normalization of low-density lipoprotein cholesterol levels. All patients with PAD should be receiving antiplatelet therapy to prevent ischemic events. Medical treatment for patients with claudication includes exercise rehabilitation and drug therapy. Although many therapies for claudication have been thoroughly investigated, research continues on new treatments. In contrast, more prospective, randomized trials are needed to evaluate various therapies for treating patients with PAD.

Developing pharmaceutical treatments for peripheral artery disease

Peripheral artery disease (PAD) is a debilitating atherosclerotic disease of the lower limbs and is associated with an increased risk of cardiovascular morbidity and mortality. Treatment goals should be aimed at providing symptom relief (claudication) and reducing the risk of systemic cardiovascular morbidity and mortality. In the development of pharmaceutical treatment for PAD, aggressive non-pharmacological intervention and pharmacological treatment of the risk factors associated with PAD should be given. Antiplatelet therapy, aspirin, should be given to every PAD patient if there are no contraindications. Should symptoms worsen or intolerance to aspirin develop, ticlopidine or clopidogrel would be the alternative. 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, small or 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 and progression of the disease, as well as the reduction in cardiovascular morbidity and mortality.

The thienopyridine derivatives (platelet adenosine diphosphate receptor antagonists), pharmacology and clinical developments

The thienopyridines, ticlopidine and clopidogrel, are antiplatelet drugs. They are prodrugs and are metabolised in the liver to active metabolites that are non-competitive antagonists of the platelet adenosine diphosphate receptor, P2Y12. Inhibition of platelet aggregation by these drugs is delayed until 24-48 h after administration, with maximal inhibition achieved after 3-5 days. Recovery of platelet function after drug withdrawal is slow (7-14 days). Ticlopidine and clopidogrel are effective in preventing atherothrombotic events in cardiovascular, cerebrovascular and peripheral vascular disease. Gastrointestinal side effects and skin rashes are common. However, neutropenia and thrombotic thrombocytopenic purpura are significant and sometimes fatal adverse effects of ticlopidine. Clopidogrel appears to offer several advantages over ticlopidine: a more rapid onset of action and a lower incidence of neutropenia and thrombotic thrombocytopenic purpura.A combination of clopidogrel and aspirin has become standard for antithrombotic therapy in cardiovascular disease. The anaesthetic considerations of patients taking the thienopyridine compounds are discussed.

Thrombotic thrombocytopenic purpura (TTP): initial treatment with plasma exchange plus steroids and immunosuppressive agents for relapsing cases

BACKGROUND

The thrombotic thrombocytopenic purpura (TTP) is a rare disorder with a high mortality rate if untreated or delayed therapy. Whether immediate diagnosis and promptly treated with plasma exchange can change the grave prognosis?

METHOD

Retrospective analysis was performed on clinical characteristics and treatment outcome of 13 patients diagnosed and treated during a 6-year period, from August 1994 to August 2000, in a tertiary care university hospital in Taiwan.

RESULTS

Among the patients, 8 were males and 5 were females, 10 were idiopathic, 2 were ticlopidine, and 1 was SLE-induced; 12 (92.3%) had neurological abnormalities, 11 (84.6%) had ecchymosis, 8 (61.5%) had fever, and 6 (46.2%) had renal impairment (creatinine > or = 1.5 mg/dL) at initial presentation of the syndrome. Excluding the SLE patient, 6 of 10 (60%) had shown antinuclear antibody (ANA) non-specific positive (titer > or = 1:40). All patients were initially treated with plasma exchange plus steroids. Of these 13 patients, 11 (84.6%) achieved complete remission, one had partial remission, and one, which was ticlopidine-induced, had no response and died of a progressive disease complicated with pneumonia. Within a median follow-up period of 31 months, 4 of 11 patients who achieved complete remission relapsed after one week, two weeks, three weeks, and three months, respectively. In the four relapsing patients, three late relapsing patients received FFP infusion, increased steroid dosages, added cyclophosphamide plus vincristine; and one early relapsing patient, relapsing twice, received an additional two courses of plasma exchange and added cyclophosphamide plus vincristine. All of the four patients achieved complete remission again. The patient who had partial remission relapsed early and responded promptly to another course of plasma exchange plus cyclophosphamide and vincristine and achieved complete remission.

CONCLUSION

Based on the results in this study, we conclude that plasma exchange plus steroids can effectively treat TTP. For patients with a refractory or relapsing disease, immunosuppressive therapy with cyclophosphamide plus vincristine should be administered as well.

Thrombotic microangiopathy in patients with acquired immunodeficiency syndrome before and during the era of introduction of highly active antiretroviral therapy

The incidence of thrombotic microangiopathy (TMA) was retrospectively evaluated in a cohort of 1223 patients with acquired immunodeficiency syndrome (AIDS) who were observed from January 1985 through December 1996 (before the era of highly active antiretroviral therapy [HAART]), and the incidence was prospectively assessed for 347 patients with AIDS during the period of January 1997 through December 2000 (during the HAART era). Seventeen cases were reported in the former cohort (1.4%). The increased risk of developing TMA was statistically significant in patients with cryptosporidiosis or AIDS-related cancer but not in those with other diseases. In the 1997-2000 cohort, no cases were observed during follow-up. TMA is associated with conditions observed in the advanced phases of human immunodeficiency virus infection. The disappearance of TMA during the HAART era may be explained by the lower percentage of patients with long-lasting CD4+ T cell depletion, advanced AIDS, or cryptosporidiosis or who have undergone multiple courses of chemotherapy for treatment of cancer.

Clinical manifestation of atherosclerotic peripheral arterial disease and the role of cilostazol in treatment of intermittent claudication

Intermittent claudication (IC) is the symptomatic expression of peripheral arterial disease (PAD), which itself is a manifestation of systemic atherosclerosis. Like other forms of atherosclerosis, PAD is associated with elevated rates of cardiovascular and cerebrovascular morbidity and mortality. Until recently, therapeutic options for the treatment of the symptoms of IC have been limited, and the efficacy of available treatment has been questioned. Cilostazol, a selective phosphodiesterase III inhibitor with vasodilator, antiplatelet, and antiproliferative properties, has recently been approved for the treatment of IC symptoms in the United States. Cilostazol significantly improves maximal and pain-free walking distances. Clinical studies have also demonstrated that cilostazol favorably alters plasma lipids (elevates HDL-cholesterol, lowers triglycerides). These properties may contribute to the benefit of this drug in IC and in other diseases secondary to atherosclerosis.

Pharmacological treatment of elderly patients with acute coronary syndromes without persistent ST segment elevation

Evidence-based management of acute coronary syndromes (ACS) without persistent ST segment elevation involves a rational, stepwise approach to the selection of therapies with potential benefit for elderly patients. Specifically, in elderly patients with ACS without persistent ST segment elevation, therapy should be administered based on the likelihood of unstable angina or non-ST elevation myocardial infarction being present and the risks and benefits of each individual therapy. All elderly patients with suspected ACS should receive anti-ischaemic therapy consisting of beta-blockers and nitrates, and antiplatelet therapy with aspirin unless clear contraindications exist. For patients with a moderate likelihood of ACS being present, defined as prior coronary disease or recurrent pain despite the use of anti-ischaemic therapies, unfractionated heparin or enoxaparin should be added to aspirin for more intense anticoagulation. In patients with high-risk clinical features, defined as ischaemic electrocardiographic changes and positive cardiac markers such as troponins, therapy with clopidogrel or glycoprotein IIb/IIIa inhibitors should be considered in addition to aspirin and heparin. Furthermore, high-risk patients should be managed with an early invasive strategy that includes prompt cardiac catheterisation within 24 to 48 hours and appropriate use of revascularisation as determined by the findings of the catheterisation. An evidence-based approach to the treatment of elderly patients with ACS without persistent ST segment elevation will help to improve the use of beneficial therapies and interventions that are recommended by current practice guidelines.

Detection of adverse drug reactions in a neurological department: comparison between intensified surveillance and a computer-assisted approach

OBJECTIVES

Adverse drug reactions (ADRs) leading to hospitalisation or occurring during hospital stay contribute significantly to patient morbidity and mortality as well as representing an additional cost for healthcare systems. The aim of this study was to provide data about the type and incidence of ADRs in a neurological department and to compare two different methodological approaches to collecting information on ADRs.

METHODS

The two methods used were intensified surveillance of neurological wards by daily ward rounds and computer-assisted screening for ADRs by means of pathological laboratory parameters.

RESULTS

Of admissions to the neurological department, 2.7% were caused by an ADR and 18.7% of patients experienced at least one ADR during hospitalisation. The positive predictive values of pathological laboratory parameters ranged between 0% (eosinophil count) and 100% for increased drug serum concentrations and international normalised ratio, i.e. the latter were always accompanied by a clinically relevant ADR. However, only half of all ADR could be detected by pathological laboratory parameters, the sensitivity of this method came to 45.1% with a specificity of 78.9%.

CONCLUSION

Similar to departments of internal medicine, a high number of ADRs occur on neurological wards. The predominant ADRs were those typical of neurotropic medications such as dyskinesia and increased sedation. Due to the age of the patients involved, cardiovascular co-medication is often prescribed and represents an additional risk factor for ADRs. By measuring pathological laboratory parameters the majority of ADRs could not be detected in neurological patients.

Thrombotic thrombocytopenic purpura and the hemolytic uremic syndrome

OBJECTIVE

To evaluate the usefulness and feasibility of measuring plasma von Willebrand factor (vWF)-cleaving metalloprotease activity (ADAMTS 13) in the differential diagnosis of thrombotic thrombocytopenic purpura (TTP), the hemolytic uremic syndrome, and other thrombotic microangiopathies.

DATA SOURCES

Articles published in the medical literature.

DATA EXTRACTION AND SYNTHESIS

In TTP, a multimeric form of vWF that is larger than that ordinarily found in the plasma may cause systemic platelet aggregation under the high-shear conditions of the microcirculation. ADAMTS 13 is a divalent cation-activated, vWF-cleaving metalloprotease that converts unusually large vWF multimers derived from endothelial cells into smaller vWF forms in normal plasma. ADAMTS 13 is severely reduced or absent in most patients with TTP. The vWF-cleaving metalloprotease is present in fresh-frozen plasma, cryoprecipitate-depleted plasma (cryosupernatant), and in plasma that has been treated with solvent and detergent. The enzyme is defective in children with chronic relapsing TTP. Infusion of any of the plasma products that contain the vWF-cleaving metalloprotease stops or prevents (for about 3 weeks) TTP episodes in these patients. An immunoglobulin (Ig) G autoantibody to the vWF-cleaving metalloprotease is found transiently in many adult patients with acquired acute idiopathic, recurrent, and ticlopidine/clopidogrel-associated TTP. Patients with acquired TTP require plasma exchange, that is, both infusion of a plasma product containing vWF-cleaving metalloprotease and removal of autoantibody and/or unusually large vWF multimers by plasmapheresis. The pathophysiology of platelet aggregation in bone marrow transplantation/chemotherapy-associated thrombotic microangiopathy, as well as in hemolytic uremic syndrome, is not established. In neither condition is there a severe decrease in plasma vWF-cleaving metalloprotease activity, as there is in TTP.

CONCLUSIONS

The presently available lengthy and complicated procedure for estimation of plasma vWF-cleaving metalloprotease activity is not yet practical for rapid diagnostic use. This test has supplanted the equally lengthy and difficult, less specific analysis of plasma vWF multimeric pattern. If the clinical distinction between TTP and hemolytic uremic syndrome is uncertain, it is appropriate to acquire (before therapy) a citrate-plasma sample for the ultimate determination of vWF-cleaving metalloprotease activity.

Stroke prevention in the elderly

The incidence of stroke and risk factors peak in subjects > or = 75 years. Highest risk patients benefit most from effective therapy. For this reason, all strategies of proven value in stroke prevention must be assiduously applied. Control of hypertension, hyperlipidemia, diabetes mellitus and cessation of cigarette smoking are obligatory at all ages but are of special importance in the elderly. Antithrombotic drugs have been proven beneficial for patients at high risk. Lower risk subjects, including those with asymptomatic carotid artery disease, gain no proven benefit from anti-platelet drugs. Patients with non-valvular atrial fibrillation (NVAF), a condition that increases with age, require anticoagulant therapy. Strict regulation of the INR is required otherwise aspirin is recommended. Without evidence of organ failure, elderly patients with severely stenotic symptomatic carotid artery disease should receive endarterectomy. They benefit most. The evidence for benefit from endarterectomy in asymptomatic subjects at any age is weak and cannot be recommended.

Successful treatment of severe thrombotic thrombocytopenic purpura with the monoclonal antibody rituximab

The only established treatment for patients with thrombotic thrombocytopenic purpura (TTP) is plasma exchange against fresh frozen plasma. For cases refractory to plasma exchange, no generally treatment schedule exists. One option is immunosuppressive therapy with corticosteroids and vincristine. Rituximab is a chimeric monoclonal antibody directed against the CD20 antigen, and it has been successfully used in B-cell malignancies and is being investigated in autoimmune diseases. Its efficacy in TTP has not yet been determined. We report two female patients with severe TTP refractory to multiple courses of plasmapheresis, high-dose steroid treatment, and vincristine who responded after adding rituximab while continuing plasmapheresis.

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.

TTP/HUS occurring in a simultaneous pancreas/kidney transplant recipient after clopidogrel treatment: evidence of a nonimmunological etiology

BACKGROUND

One recently reported thrombotic thrombocytopenia purpura/hemolytic uremic syndrome (TTP/HUS) case involved a patient who underwent simultaneous pancreas/kidney (SPK) transplant followed by pancreas rejection and clopidogrel treatment, an antiplatelet agent that has been associated with immunologically mediated TTP/HUS. We present a second case of TTP/HUS developing in an SPK recipient who was also receiving clopidogrel.

METHODS

After a stroke, a 48-year-old male SPK transplant recipient received clopidogrel. Four months later, thrombosis and rejection of the transplanted pancreas occurred. One week after a pancreatectomy, TTP/HUS developed that resolved with clopidogrel and sirolimus discontinuation and lowering of the tacrolimus dose.

RESULTS

A plasma sample revealed von Willebrand factor cleaving metalloproteinase activity, although no immunoglobulins to the protease were identified. The patient continues taking tacrolimus with normal renal function 1 year after the incident.

DISCUSSION

Our findings suggest a nonimmunological etiology for TTP/HUS in clopidogrel-treated transplant recipients. Furthermore, mechanistic focused laboratory studies can facilitate interpretation of case report findings.

Pharmacotherapeutic options for the management of myocardial infarction

The pharmacological treatment of acute coronary syndrome (ACS), including unstable angina, non-ST- and ST-segment elevation myocardial infarction (MI) is dynamic and continues to evolve. Expert guidelines based on the results of clinical trials for the management of different types of ACS have been published. In both ST-segment elevation and non-ST-segment elevation MI, aspirin/clopidogrel, heparin/low molecular weight heparin/direct thrombin inhibitors, beta-blockers and angiotensin converting enzyme inhibitors are part of the routine regimens. In patients with ST-segment elevation MI, eligibility for thrombolytic therapy needs to be determined and utilised as soon as possible. In patients with non-ST-segment elevation MI, the risks of thrombolytic therapy outweigh the benefits. The use of glycoprotein IIb/IIIa inhibitors has become increasingly important. The use of antihyperlipidaemic agents for the prevention of secondary events in both types of patients continue to be essential and the early aggressive use of lipid-lowering therapy also plays a role in improving endothelial function and stabilising atherosclerotic plaques.

Plasmapheresis in thrombotic microangiopathy-associated syndromes: review of outcome data derived from clinical trials and open studies

Current reimbursement policy of health insurance for therapeutic plasmapheresis requires proof of efficacy using the concept of evidence-based medicine. The aim of this paper is to review the outcome of plasmapheresis used to treat thrombotic microangiopathy (TMA)-associated syndromes in the last decade to provide scientific evidence to back up reimbursement applications. The strength of evidence of each reviewed study was assessed using the five levels of evidence criteria as defined by the American Society of Hematology in 1996 for assessment of the treatment of immune thrombocytopenia. The level Experimental indication was added for situations where only case reports or small series supported by pathophysiological reasoning are available. The definitions of evidence used in this paper are as follows: Level I, randomized clinical trial with low rates of error (p < 0.01); Level II, randomized clinical trial with high rates of error (p < 0.05); Level III, nonrandomized studies with concurrent control group; Level IV, nonrandomized studies with historical control group; Level V, case series without a control group or expert opinion; and Experimental, case reports and pathophysiological reasoning. The results of this analysis based on the published data is summarized as follows: The indication of plasmapheresis is assigned to Level IV evidence for thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS); cancer/chemotherapy-associated TTP/HUS is assigned to Level V evidence; and TTP/HUS refractory to standard plasma exchange and post-bone marrow transplantation TTP/HUS are assigned to Experimental indication. For both subsets, protein A immunoadsorption is reportedly successful. The other TMA-associated syndromes, hemolysis elevated liver enzymes low platelets and HUS in early childhood, are no indication of plasmapheresis. Two randomized clinical trials were performed in order to demonstrate the superiority of plasma exchange/fresh frozen plasma (PEX/FFP) over plasma transfusion in the management of TTP/HUS. The results prove the greater clinical success of the latter type of plasma administration. Standard PEX/FFP has reduced the mortality of TTP/HUS from 94.5% to 13%.

Transient ischemic attacks: an emergency medicine approach

Recent advances in TIA research provide emergency physicians a new understanding of the disease process. Untreated or under-treated patients with TIA are at significant risk. Prompt and thorough evaluation must be undertaken to prevent devastating harm to this group of patients. This is truly a paradigm shift for many physicians, and one area in which emergency physicians lead in education and patient advocacy. The authors wish to acknowledge Dr. Stewart Wright, Dr. Alex Schneider, and Dr. Dawn Kleindorfer for their expert review, and Amy Hess for her assistance in the preparation of this manuscript.

Structure toxicity relationships--how useful are they in predicting toxicities of new drugs?

This chapter provides just a few newer examples of structural moieties found in drugs that have been associated with reactive metabolite formation and toxicities. For a discussion of several other structures in drugs that undergo metabolic activation to reactive intermediates, the reader is directed to previous volumes in this series and other chapters in this book, as well as a previous condensed review (Nelson, 1982). Since that review, some new knowledge allows us to better predict that some structural moieties are more likely than others to form drug reactive metabolites that may be involved in causing toxic effects in humans. For example, most aniline-, thiophene-, and nitroaromatic-containing drugs have had a relatively high incidence of adverse effects, and it would be prudent in the drug discovery process to avoid these substructures if possible. However, as illustrated by the case of olanzapine, these structures may be important for potent activity, and could therefore be beneficial in some cases. The glitazones represent a new class of drugs with a unique thiazolidinedione structure. This raises two important points. First, it demonstrates how limited our knowledge base is in regard to structure toxicity relationships when new structures are introduced. Our approaches must be very empirical and are far from quantitative for the reasons outlined in the introduction. Secondly, the glitazones point out the importance of benefit/risk considerations. This was a new structural class of drugs with a unique spectrum of action that is very beneficial in the treatment of a major disease. Despite some suspected risk of toxicity, based on early trials, troglitazone was approved for use with careful monitoring. This author believes that was the right decision, as was the decision to withdraw the drug when the risk became unacceptable, especially with the introduction of safer alternatives. If this were just another NSAID (e.g., bromfenac), there would be little reason for approval. In summary, as I pointed out previously (Nelson, 1982), with our limited knowledge of structure toxicity relationships, we can only make reasonable judgments as to risk assessment of a new drug in humans, and hope that we neither release a dangerous chemical entity nor, as importantly, abort an effective one.