Delayed thrombocytopenia after treatment with abciximab: a distinct clinical entity associated with the immune response to the drug

Delayed-onset eptifibatide-induced thrombocytopenia

PURPOSE

We present a unique case of delayed-onset, profound eptifibatide-induced thrombocytopenia that occurred 5 days after initiation of the drug.

SUMMARY

Eptifibatide is a platelet glycoprotein IIb/IIIa receptor inhibitor with indications for use in patients with acute coronary syndromes. Eptifibatide-induced thrombocytopenia is uncommon but well studied and typically occurs within 24 hours of initiation of the drug. In the case described here, a 62-year-old male with a past history of coronary artery disease (including percutaneous coronary intervention within the past 12 months) was started on eptifibatide at a dosage of 2 µg/kg per minute for management of significant thrombus burden prior to a planned cardiac revascularization procedure; heparin for anticoagulation was also initiated. About 5 days after initiation of eptifibatide, the patient developed severe thrombocytopenia, with the platelet count dropping precipitously from 249 × 103/µL on admission to less than 1 × 103/µL. After eptifibatide and heparin therapy were discontinued and the patient was switched to argatroban, the platelet count recovered to 38 × 103/µL over the next 2 days. An eptifibatide platelet antibody assay was positive for IgG-mediated reactions consistent with eptifibatide-induced thrombocytopenia. Scoring of this case with the Naranjo scale yielded a score of 4, suggesting a possible adverse reaction to eptifibatide.

CONCLUSION

This is the first published case report of profound eptifibatide-induced thrombocytopenia occurring more than 24 hours after eptifibatide initiation and serves to bring awareness that a delayed reaction can occur.

Clinical pharmacology of antiplatelet drugs

INTRODUCTION

Platelets play a key role in arterial thrombosis and antiplatelet therapy is pivotal in the treatment of cardiovascular disease. Current antiplatelet drugs target different pathways of platelet activation and show specific pharmacodynamic and pharmacokinetic characteristics, implicating clinically relevant drug-drug interactions.

AREAS COVERED

This article reviews the role of platelets in hemostasis and cardiovascular thrombosis, and discusses the key pharmacodynamics, drug-drug interactions and reversal strategies of clinically used antiplatelet drugs.

EXPERT OPINION

Antiplatelet therapies target distinct pathways of platelet activation: thromboxane A₂ synthesis, adenosine diphosphate-mediated signaling, integrin α_IIbβ₃ (GPIIb/IIIa), thrombin-mediated platelet activation via the PAR1 receptor and phosphodiesterases. Key clinical drug-drug interactions of antiplatelet agents involve acetylsalicylic acid - ibuprofen, clopidogrel - omeprazole, and morphine - oral P2Y₁₂ inhibitors, all of which lead to an attenuated antiplatelet effect. Platelet function and genetic testing and the use of scores (ARC-HBR, PRECISE-DAPT, ESC ischemic risk definition) may contribute to a more tailored antiplatelet therapy. High on-treatment platelet reactivity presents a key problem in the acute management of ST-elevation myocardial infarction (STEMI). A treatment strategy involving early initiation of an intravenous antiplatelet agent may be able to bridge the gap of insufficient platelet inhibition in high ischemic risk patients with STEMI.

A Data-Driven Medical Decision Framework for Associating Adverse Drug Events with Drug-Drug Interaction Mechanisms

Adverse drug events (ADEs) occur when multiple drugs interact within an individual, thus causing effects that were not initially predicted. Such toxic interactions lead to morbidity and mortality. Contemporary research surrounding ADEs has tended to focus on the detection of potential ADEs without great concern for elucidating the associations of drug-drug interaction (DDI) mechanisms that can predict potential adverse drug reactions (ADRs). Such associations are of great practical importance for everyday pharmacovigilance efforts. This study presents a data-driven framework for conducting knowledge-driven data analysis that combines a semantic inference system and enrichment analysis in order to identify potential ADE mechanisms. The framework was used to rank mechanisms according to their relevance for DDIs and also to categorize ADEs based on the number of DDI mechanism associations identified through enrichment analysis. Its validity is demonstrated through using both commercial and publicly available DDI resources. The results of this study solidly prove the framework's effectiveness and highlight potential for future research by way of incorporating additional and broader data to deepen and expand its capabilities.

Subvisible Particles in Solutions of Remicade in Intravenous Saline Activate Immune System Pathways in In Vitro Human Cell Systems

Among patients that receive Remicade® therapy, more than 20% have adverse infusion related reactions and approximately 50% have immunogenic responses.^1-3 Upon characterization of initial Remicade®-IV solution we observed a high concentration of subvisible particles that could inadvertently be delivered to patients. This solution was processed through the IV infusion system, mimicking the typical clinical administration setup - either with or without an in-line filter connected to the IV line. The samples generated thereafter were tested using various in vitro assays for activation of the innate immune system via cytokine release in whole blood and in peripheral blood mononuclear cell (PBMC) cultures, and activation of the Toll like receptors (TLRs). Activation of the adaptive immune system was evaluated by monitoring upregulation of surface receptors on dendritic cells (DCs) and CD4+ T cell proliferation in response to IV solution of Remicade®. Our results indicate that subvisible particles in Remicade®-saline solution have a significant role in activation of the immune system but there are extrinsic factors potentially contributed by the in-line filters or other process parameters that also contribute to immune system activation.

Delayed thrombocytopenia following administration of abciximab: Pharmacovigilance survey and literature review

BACKGROUND

Abciximab (ABX) is used for acute coronary syndrome and unstable angina. Thrombocytopenia is a frequent adverse effect described as occurring in the first 24hours. The aim of this study was to evaluate, in a context of pharmacovigilance survey, the occurrence of delayed thrombocytopenia following ABX infusion in pharmacovigilance database reports and in the literature.

METHODS

Individual case safety reports (ICSRs) of delayed thrombocytopenia-between 3 and 30 days - with ABX presented as a single suspect were selected in VigiBase®, the WHO global database of ICSRs. The French cases were then extracted from the French national pharmacovigilance database. In addition, a literature review of published cases was performed using PubMed.

RESULTS

Among the 84 ICSRs selected from VigiBase®, 43 were also reported in the FPVD. Mean age was 60.1±12.3 years with a majority of male patients (77.4%). The average time to onset (TTO) was 8.9±5.2 days. Thrombocytopenia regressed in 5.1±2.7 days. Haemorrhagic complications were reported in 15% of ICSRs. In the French cases, the median nadir of platelet count was 28×10⁹/L (range 1-110) with a majority of grade 4 thrombocytopenia (39.5%). The literature review identified 42 cases and provided additional information on administered therapies, which include platelet units, corticosteroids, and IV immunoglobulins. GPIIb/IIIa-ABX complex antibodies were described in 26 published cases.

CONCLUSION

Delayed thrombocytopenia, probably due to immune reaction, is a possible life-threatening adverse effect of ABX with a mean TTO of 9 days, supporting the recommendation of a platelet count monitoring during at least two weeks. This recommendation was added to the abcximab SmPC in 2019.

Efficacy and safety of abciximab versus tirofiban in addition to ticagrelor in STEMI patients undergoing primary percutaneous intervention

Platelet glycoprotein IIb/IIIa inhibitors (GPIs) have been part of the adjuvant treatment of acute coronary syndrome for years. However, real-life data regarding the efficacy and safety of GPIs under the current indications are lacking in the setting of potent platelet inhibition. The objectives were to assess the efficacy and safety of abciximab versus tirofiban in patients with ST-elevation acute myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI) and pretreated with ticagrelor, and to identify independent predictor factors of efficacy, bleeding and platelet drop. Three hundred sixty-two patients were divided by GPI administered. Clinical, laboratory, angiographic and outcome characteristics were compared. The primary objective was a composite efficacy endpoint (death from any cause, nonfatal myocardial infarction and nonfatal stroke) at 30 days. The secondary objectives were its individual components, safety (bleeding) and the impact on platelet count during hospital stay. The composite efficacy endpoint was similar in the abciximab and tirofiban groups (6.1% vs 7.3%; p = .632). There were also no differences in cardiovascular death (2.5% vs 2.4%; p = .958), nonfatal myocardial infarction (3% vs 4.3%; p = .521) and nonfatal stroke (0.5% vs 1.8%; p = .332). Tirofiban administration was associated with a higher incidence of bleeding (11.6% vs 22%; p = .008) with no differences in BARC ≥ 3b bleeding (3.6 vs 2.5%; p = .760). In STEMI patients undergoing PPCI with ticagrelor, abciximab and tirofiban had similar rates in the composite efficacy endpoint at 30 days. The 30-day bleeding rate was significantly higher in the tirofiban group. Tirofiban administration was an independent predictor of both bleeding and platelet count drop.

Thrombocytopenia induced by glycoprotein (GP) IIb-IIIa antagonists: about two cases

In this paper, we report two cases of induced thrombocytopenia after the infusion of glycoprotein (GP) IIb/IIIa receptors antagonists, following a coronary angioplasty. The first patient is a 65-year-old woman, admitted with acute coronary syndrome requiring percutaneous angioplasty with stenting. The patient was given tirofiban + unfractionated heparin (UFH). Ten hours later, the patient revealed very severe thrombocytopenia and went into hemorrhagic shock (hematemesis and hematoma at the injection site). The patient was transfused with nine units of red blood cells (RBCs), 24 platelets pellets and 4 units of fresh frozen plasma (FFP). The second patient is a 76-year-old woman. She was admitted to hospital for acute coronary syndrome necessitating percutaneous angioplasty with stenting and a glycoprotein IIb/IIIa receptor antagonists, tirofiban + unfractionated (UFH). Four hours later, the patient presented with gingivorrhagia associated thrombocytopenia. She received six platelet pellets transfusion with well clinical and biological improvement. These two observations raise the significance of a close monitoring of platelet count after the initiation of GP IIb/IIIa antagonists infusion, which are sometimes responsible for life-threatening adverse events.

Pathophysiology and Diagnosis of Drug-Induced Immune Thrombocytopenia

Drug-induced immune thrombocytopenia (DITP) is a life-threatening clinical syndrome that is under-recognized and difficult to diagnose. Many drugs can cause immune-mediated thrombocytopenia, but the most commonly implicated are abciximab, carbamazepine, ceftriaxone, eptifibatide, heparin, ibuprofen, mirtazapine, oxaliplatin, penicillin, quinine, quinidine, rifampicin, suramin, tirofiban, trimethoprim-sulfamethoxazole, and vancomycin. Several different mechanisms have been identified in typical DITP, which is most commonly characterized by severe thrombocytopenia due to clearance and/or destruction of platelets sensitized by a drug-dependent antibody. Patients with typical DITP usually bleed when symptomatic, and biological confirmation of the diagnosis is often difficult because detection of drug-dependent antibodies (DDabs) in the patient's serum or plasma is frequently not possible. This is in contrast to heparin-induced thrombocytopenia (HIT), which is a particular DITP caused in most cases by heparin-dependent antibodies specific for platelet factor 4, which can strongly activate platelets in vitro and in vivo, explaining why affected patients usually have thrombotic complications but do not bleed. In addition, laboratory tests are readily available to diagnose HIT, unlike the methods used to detect DDabs associated with other DITP that are mostly reserved for laboratories specialized in platelet immunology.

Species-Specific Involvement of Integrin αIIbβ3 in a Monoclonal Antibody CH12 Triggers Off-Target Thrombocytopenia in Cynomolgus Monkeys

CH12 is a novel humanized monoclonal antibody against epidermal growth factor receptor variant III (EGFRvIII) for cancer treatment. Unfortunately, in pre-clinical safety evaluation studies, acute thrombocytopenia was observed after administration of CH12 in cynomolgus monkeys, but not rats. More importantly, in vitro experiments found that CH12 can bind and activate platelets in cynomolgus monkey, but not human peripheral blood samples. Cynomolgus monkey-specific thrombocytopenia has been reported previously; however, the underlying mechanism remains unclear. Here, we first showed that CH12 induced thrombocytopenia in cynomolgus monkeys through off-target platelet binding and activation, resulting in platelet destruction. We subsequently found that integrin αIIbβ3 (which is expressed on platelets) contributed to this off-target toxicity. Furthermore, three-dimensional structural modeling of the αIIbβ3 molecules in cynomolgus monkeys, humans, and rats suggested that an additional unique loop exists in the ligand-binding pocket of the αIIb subunit in cynomolgus monkeys, which may explain why CH12 binds to platelets only in cynomolgus monkeys. Moreover, this study supported the hypothesis that the minor differences between cynomolgus monkeys and humans can confuse human risk assessments and suggests that species differences can help the prediction of human risks and avoid losses in drug development.

Abciximab-induced delayed profound thrombocytopaenia

Abciximab, the first approved glycoprotein (GP IIb/IIIa) inhibitor, is being widely used during acute coronary syndromes and offers the promising approach to antithrombotic therapy. We present a case of a young woman who initially received abciximab infusion for undergoing percutaneous coronary intervention of left anterior descending artery and was eventually diagnosed with abciximab-induced delayed thrombocytopaenia. This case outlines the importance of close follow-up of these patients to prevent serious adverse events.

Clinical picture of heparin-induced thrombocytopenia (HIT) and its differentiation from non-HIT thrombocytopenia

HIT is an acquired antibody-mediated disorder strongly associated with thrombosis, including microthrombosis secondary to disseminated intravascular dissemination (DIC). The clinical features of HIT are reviewed from the perspective of the 4Ts scoring system for HIT, which emphasises its characteristic timing of onset of thrombocytopenia. HIT antibodies recognize multimolecular complexes of platelet factor 4 (PF4)/heparin. However, a subset of HIT sera recognise PF4 bound to platelet chondroitin sulfate; these antibodies activate platelets in vitro and in vivo even in the absence of heparin, thus explaining: delayed-onset HIT (where HIT begins or worsens after stopping heparin); persisting HIT (where HIT takes several weeks to recover); spontaneous HIT syndrome (a disorder clinically and serologically resembling HIT but without proximate heparin exposure); and fondaparinux-associated HIT (four distinct syndromes featuring thrombocytopenia that begins or worsens during treatment with fondaparinux), with a new patient case presented with ongoing thrombocytopenia (and fatal haemorrhage) during treatment of HIT with fondaparinux, with fondaparinux-dependent platelet activation induced by patient serum ("fondaparinux cross-reactivity"). Ironically, despite existence of fondaparinux-associated HIT, this pentasaccharide anticoagulant is a frequent treatment for HIT (including one used by the author). HIT can be confused with other disorders, including those with a) timing similar to HIT (e. g. abciximab-associated thrombocytopenia of delayed-onset); b) combined thrombocytopenia/thrombosis (e. g. symmetrical peripheral gangrene secondary to acute DIC and shock liver); and c) both timing of onset and thrombosis (e. g. warfarin-associated venous limb gangrene complicating cancer-associated DIC). By understanding clinical and pathophysiological similarities and differences between HIT and non-HIT mimicking disorders, the clinician is better able to make the correct diagnosis.

Hypersensitivity reactions to modern antiplatelet and anticoagulant drugs

Anticoagulation and antiplatelet drugs are among the most commonly used medical drugs. In addition to the long-established heparins, hirudins, coumarins and antiplatelet drugs such as acetylsalicylic acid, numerous novel and predominantly synthetic pharmacologic agents have come onto the market in recent years. These new agents act at various sites in coagulation and have significantly broadened treatment options. Whilst immunological hypersensitivity reactions are on the whole rare, they have a considerable impact on patient management when they do occur. The present overview discusses the currently known hypersensitivity reactions to anticoagulant and antiplatelet agents, with particular attention to the newer substance classes including P2Y₁₂ inhibitors, glycoprotein IIb/IIIb receptor antagonists, direct factor Xa inhibitors and direct thrombin inhibitors.

Drug-induced immune thrombocytopenia: incidence, clinical features, laboratory testing, and pathogenic mechanisms

Drug-induced immune thrombocytopenia (DIIT) is a relatively uncommon adverse reaction caused by drug-dependent antibodies (DDAbs) that react with platelet membrane glycoproteins only when the implicated drug is present. Although more than 100 drugs have been associated with causing DIIT, recent reviews of available data show that carbamazepine, eptifibatide, ibuprofen, quinidine, quinine, oxaliplatin, rifampin, sulfamethoxazole, trimethoprim, and vancomycin are probably the most frequently implicated. Patients with DIIT typically present with petechiae, bruising, and epistaxis caused by an acute, severe drop in platelet count (often to <20,000 platelets/pL). Diagnosis of DIIT is complicated by its similarity to other non-drug-induced immune thrombocytopenias, including autoimmune thrombocytopenia, posttransfusion purpura, and platelet transfusion refractoriness, and must be differentiated by temporal association of exposure to a candidate drug with an acute, severe drop in platelet count. Treatment consists of immediate withdrawal of the implicated drug. Criteria for strong evidence of DIIT include (1) exposure to candidate drug-preceded thrombocytopenia; (2) sustained normal platelet levels after discontinuing candidate drug; (3) candidate drug was only drug used before onset of thrombocytopenia or other drugs were continued or reintroduced after resolution of thrombocytopenia, and other causes for thrombocytopenia were excluded; and (4) reexposure to the candidate drug resulted in recurrent thrombocytopenia. Flow cytometry testing for DDAbs can be useful in confirmation of a clinical diagnosis, and monoclonal antibody enzyme-linked immunosorbent assay testing can be used to determine the platelet glycoprotein target(s), usually GPIIb/IIIa or GPIb/IX/V, but testing is not widely available. Several pathogenic mechanisms for DIIT have been proposed, including hapten, autoantibody, neoepitope, drug-specific, and quinine-type drug mechanisms. A recent proposal suggests weakly reactive platelet autoantibodies that develop greatly increased affinity for platelet glycoprotein epitopes through bridging interactions facilitated by the drug is a possible mechanism for the formation and reactivity of quinine- type drug antibodies.

Approach to the diagnosis and management of drug-induced immune thrombocytopenia

Drug-induced immune thrombocytopenia (DITP) is a challenging clinical problem that is under-recognized, difficult to diagnose and associated with severe bleeding complications. DITP may be caused by classic drug-dependent platelet antibodies (eg, quinine); haptens (eg, penicillin); fiban-dependent antibodies (eg, tirofiban); monoclonal antibodies (eg, abciximab); autoantibody formation (eg, gold); and immune complex formation (eg, heparin). A thorough clinical history is essential in establishing the diagnosis of DITP and should include exposures to prescription medications, herbal preparations and even certain foods and beverages. Clinical and laboratory criteria have been established to determine the likelihood of a drug being the cause of thrombocytopenia, but these criteria can only be applied retrospectively. The most commonly implicated drugs include quinine, quinidine, trimethoprim/sulfamethoxazole and vancomycin. We propose a practical approach to the diagnosis of the patient with suspected DITP. Key features are: the presence of severe thrombocytopenia (platelet nadir <20×10(9)/L); bleeding complications; onset 5 to 10days after first drug exposure, or within hours of subsequent exposures or after first exposure to fibans or abciximab; and exposure to drugs that have been previously implicated in DITP reactions. Treatment involves stopping the drug(s), administering platelet transfusions or other therapies if bleeding is present and counselling on future drug avoidance. The diagnosis can be confirmed by a positive drug re-challenge, which is often impractical, or by demonstrating drug-dependent platelet reactive antibodies in vitro. Current test methods, which are mostly flow cytometry-based, must show drug-dependence, immunoglobulin binding, platelet specificity and ideally should be reproducible across laboratories. Improved standardization and accessibility of laboratory testing should be a focus of future research.

Drug-induced immune thrombocytopenia

Thrombocytopenia is caused by immune reactions elicited by diverse drugs in clinical practice. The activity of the drug-dependent antibodies produces a marked decrease in blood platelets and a risk of serious bleeding. Understanding of the cellular mechanisms that drive drug-induced thrombocytopenia has advanced recently but there is still a need for improved laboratory tests and treatment options. This article provides an overview of the different types of drug-induced thrombocytopenia, discusses potential pathologic mechanisms, and considers diagnostic methods and treatment options.

How to approach thrombocytopenia

Thrombocytopenia is a common hematologic finding with variable clinical expression. A low platelet count may be the initial manifestation of infections such as HIV and hepatitis C virus or it may reflect the activity of life-threatening disorders such as the thrombotic microangiopathies. A correct identification of the causes of thrombocytopenia is crucial for the appropriate management of these patients. In this review, we present a systematic evaluation of adults with thrombocytopenia. The approach is clearly different between outpatients, who are frequently asymptomatic and in whom we can sometimes indulge in sophisticated and relatively lengthy investigations, and the dramatic presentation of acute thrombocytopenia in the emergency department or in the intensive care unit, which requires immediate intervention and for which only a few diagnostic tests are available. A brief discussion of the most common etiologies seen in both settings is provided.

Thrombocytopenia following percutaneous coronary intervention

BACKGROUND

Thrombocytopenia following percutaneous coronary intervention (PCI) is an underappreciated condition that is often clinically challenging. There are no guidelines on the management of patients with this condition.

OBJECTIVE

To review recent data in etiologies, risk factors, prevention, management, and prognostic implications of thrombocytopenia following PCI.

EVIDENCE ACQUISITION

Search of MEDLINE, EMBASE, the Cochrane Database, and Google Scholar using the term thrombocytopenia + PCI and other relevant keywords to identify systematic reviews, clinical trials, cohort studies, case series, and case reports. The review was limited to English-language articles published between January 1980 and June 2009. Articles on patients with baseline thrombocytopenia prior to PCI were excluded.

EVIDENCE SYNTHESIS

Thrombocytopenia is not infrequent following PCI. The typical patient with post-PCI thrombocytopenia is on multiple therapies that can potentially cause a decrease in the platelet count. Identification of the cause is critical because management of the condition varies significantly based on the etiology. The severity of the thrombocytopenia also determines the clinical management of the patient. Several observational studies have demonstrated the adverse prognostic impact of the complication on clinical outcomes and have identified risk factors.

CONCLUSIONS

Judicious use of therapies that can cause thrombocytopenia, efficient detection of the cause of the decrease in platelet count, and appropriate management of the condition can potentially improve the quality of care and outcomes following PCI. Further research into risk factors that predispose post-PCI patients to developing thrombocytopenia is warranted.

The safety and side effects of monoclonal antibodies

Monoclonal antibodies (mAbs) are now established as targeted therapies for malignancies, transplant rejection, autoimmune and infectious diseases, as well as a range of new indications. However, administration of mAbs carries the risk of immune reactions such as acute anaphylaxis, serum sickness and the generation of antibodies. In addition, there are numerous adverse effects of mAbs that are related to their specific targets, including infections and cancer, autoimmune disease, and organ-specific adverse events such as cardiotoxicity. In March 2006, a life-threatening cytokine release syndrome occurred during a first-in-human study with TGN1412 (a CD28-specific superagonist mAb), resulting in a range of recommendations to improve the safety of initial human clinical studies with mAbs. Here, we review some of the adverse effects encountered with mAb therapies, and discuss advances in preclinical testing and antibody technology aimed at minimizing the risk of these events.

Adverse drug reactions affecting blood cells

Numerous medications and other xenobiotics are capable of producing adverse reactions (ADRs) affecting red cells, platelets or neutrophils. Occasionally, more than one blood element is affected simultaneously. As with all drug reactions, some side effects are a direct consequence of a known pharmacologic action of the drug and are dose-dependent; others occur sporadically and relatively independent of dose. The latter ("idiosyncratic") reactions are unpredictable and, in general, have no known underlying genetic basis. Many are antibody-mediated, as would be expected since cellular immune effector cells have little direct access to circulating blood cells. In this chapter, we will discuss idiosyncratic drug reactions affecting blood and blood forming tissues with an emphasis on those thought to be immune-mediated.

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.

Pathobiology of secondary immune thrombocytopenia

Primary immune thrombocytopenic purpura (ITP) remains a diagnosis of exclusion both from nonimmune causes of thrombocytopenia and immune thrombocytopenia that develops in the context of other disorders (secondary immune thrombocytopenia). The pathobiology, natural history, and response to therapy of the diverse causes of secondary ITP differ from each other and from primary ITP, so accurate diagnosis is essential. Immune thrombocytopenia can be secondary to medications or to a concurrent disease, such as an autoimmune condition (eg, systemic lupus erythematosus [SLE], antiphospholipid antibody syndrome [APS], immune thyroid disease, or Evans syndrome), a lymphoproliferative disease (eg, chronic lymphocytic leukemia or large granular T-lymphocyte lymphocytic leukemia), or chronic infection, eg, with Helicobacter pylori, human immunodeficiency virus (HIV), or hepatitis C virus (HCV). Response to infection may generate antibodies that cross-react with platelet antigens (HIV, H pylori) or immune complexes that bind to platelet Fcγ receptors (HCV), and platelet production may be impaired by infection of megakaryocyte (MK) bone marrow–dependent progenitor cells (HCV and HIV), decreased production of thrombopoietin (TPO), and splenic sequestration of platelets secondary to portal hypertension (HCV). Sudden and severe onset of thrombocytopenia has been observed in children after vaccination for measles, mumps, and rubella or natural viral infections, including Epstein-Barr virus, cytomegalovirus, and varicella zoster virus. This thrombocytopenia may be caused by cross-reacting antibodies and closely mimics acute ITP of childhood. Proper diagnosis and treatment of the underlying disorder, where necessary, play an important role in patient management.

Drug-induced immune thrombocytopenia: pathogenesis, diagnosis, and management

Drug-induced immune thrombocytopenia (DITP) can be triggered by a wide range of medications. Although many cases of DITP are mild, some are characterized by life-threatening bleeding symptoms. The pathogenesis of DITP is complex, in that at least six different mechanisms have been proposed by which drug-induced antibodies can promote platelet destruction. It is possible in many cases to identify antibodies that react with platelets in the presence of the sensitizing drug, but the required testing is technically demanding and not widely available. Therefore, a decision on whether to discontinue an implicated medication in a patient suspected of having DITP must be made on clinical grounds. An algorithm is available that can be helpful in assessing the likelihood that a particular drug caused thrombocytopenia, but the most important aspects of patient management are a high index of suspicion and a careful history of drug exposure in an individual who presents with acute, often severe thrombocytopenia of unknown etiology. How drugs induce platelet-reactive antibodies and how, once formed, the antibodies cause platelet destruction following exposure to the drug is poorly understood. Further studies to address these issues and characterize more completely the range of drugs and drug metabolites that can cause DITP are needed.

Acute profound thrombocytopenia with second exposure to eptifibatide associated with a strong antibody reaction

We present a case of eptifibatide-induced acute profound thrombocytopenia in a 64-year-old male receiving eptifibatide for the second time during percutaneous coronary intervention. Although rare, short and self-limited episodes of acute and profound thrombocytopenia have been associated with eptifibatide exposure. The thrombocytopenia is thought to be immune mediated, and assays are available to test for eptifibatide-induced platelet antibodies.

Drug-induced thrombocytopenia

Drug-induced thrombocytopenia was first described in the 19th century, yet our understanding of its pathogenesis continues to evolve. The list of drugs implicated in drug-induced thrombocytopenia is extensive and growing. Many, if not most, of these medications induce thrombocytopenia by immune mechanisms. Because the degree of thrombocytopenia can put patients at risk for serious bleeding, a prompt diagnosis is key to clinical management. The laboratory approach to diagnosing drug-induced thrombocytopenia is 2-pronged. First, nondrug causes of thrombocytopenia must be ruled out. Second, testing for drug-dependent platelet antibodies, available at specialized reference laboratories, often can identify the offending medication, although usually not in time for initial clinical management. Once a medication is suspected of causing thrombocytopenia, it must be discontinued promptly, and the patient should be monitored closely. Thrombocytopenia generally resolves quickly after offending medication withdrawal, and the prognosis of drug-induced thrombocytopenia is then excellent.

Drug-induced thrombocytopenia: pathogenesis, evaluation, and management

Although drugs are a common cause of acute immune-mediated thrombocytopenia in adults, the drug etiology is often initially unrecognized. Most cases of drug-induced thrombocytopenia (DITP) are caused by drug-dependent antibodies that are specific for the drug structure and bind tightly to platelets by their Fab regions but only in the presence of the drug. A comprehensive database of 1301 published reports describing 317 drugs, available at www.ouhsc.edu/platelets, provides information on the level of evidence for a causal relation to thrombocytopenia. Typically, DITP occurs 1 to 2 weeks after beginning a new drug or suddenly after a single dose when a drug has previously been taken intermittently. However, severe thrombocytopenia can occur immediately after the first administration of antithrombotic agents that block fibrinogen binding to platelet GP IIb-IIIa, such as abciximab, tirofiban, and eptifibatide. Recovery from DITP usually begins within 1 to 2 days of stopping the drug and is typically complete within a week. Drug-dependent antibodies can persist for many years; therefore, it is important that the drug etiology be confirmed and the drug be avoided thereafter.

Flow cytometry in the diagnosis of drug-induced thrombocytopenia: two illustrative cases

Drug-induced thrombocytopenia is a challenging diagnosis in the clinical practice because of the many drugs or alternative causes that may be implicated. Exact identification of such drug(s) is required to guide future management and avoid re-exposure. We describe two cases of isolated thrombocytopenia in which cytometric analysis, a readily available technique, allowed the identification of the causative drug in the context of complex therapies (rifampicin and abciximab causing late onset thrombocytopenia).

Hypersensitivity reactions to biological agents with special emphasis on tumor necrosis factor-alpha antagonists

PURPOSE OF REVIEW

Several biological agents have been introduced into the drug market and more are emerging. Adverse reactions to these agents have recently been classified into five different subtypes. Some of these reactions are frequent but without consequences for the patients. Others are less frequent but potentially life-threatening, and they include allergic reactions.

RECENT FINDINGS

Hypersensitivity reactions are well described adverse drug reactions, corresponding to the ss-type of the newly proposed classification of adverse reactions induced by biological agents. We focus our search on tumor necrosis factor-alpha antagonists, as they represent a dramatic improvement in the therapy of both rheumatic and inflammatory bowel diseases and because adverse reactions have been closely scrutinized. We also add cases from our own experience. We found very few properly documented allergic reactions.

SUMMARY

Hypersensitivity reactions to tumor necrosis factor-alpha antagonists are not rare. Whether these manifestations have to be considered type beta or type gamma reactions is still a matter of debate. There is a need for allergological tests in vivo and in vitro.

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.

Drug-induced thrombocytopenia

Drug-induced thrombocytopenia (DIT) is a relatively common clinical disorder. It is imperative to provide rapid identification and removal of the offending agent before clinically significant bleeding or, in the case of heparin, thrombosis occurs. DIT can be distinguished from idiopathic thrombocytopenic purpura, a bleeding disorder caused by thrombocytopenia not associated with a systemic disease, based on the history of drug ingestion or injection and laboratory findings. DIT disorders can be a consequence of decreased platelet production (bone marrow suppression) or accelerated platelet destruction (especially immune-mediated destruction).

Glycoprotein IIb/IIIa inhibitor-induced thrombocytopenia

Thrombocyte glycoprotein IIb/IIIa inhibitors prevent fibrinogen binding and thereby thrombocyte aggregation. The inhibition of thrombocyte activation at the damaged coronary plaque is the target of the new therapeutic strategies in treating acute coronary syndrome. This reduces the ischemic complications associated with the non-STelevation myocardial infarction (NSTEMI) and percutaneous coronary intervention (PCI). Thrombocytopenia is a known complication of glycoprotein (GP) IIb/IIIa inhibitors. Although, in general, GP IIb/IIIa inhibitor-induced thrombocytopenia is a harmless side effect which responds readily to thrombocyte transfusion, it can occasionally be a very serious complication associated with serious bleeding. In addition patients developing thrombocytopenia have unfavorable outcome (e.g., death, myocardial infarction, bypass surgery or additional PCI) in comparison to patients without thrombocytopenia. Advanced age (> 65 years), low BMI and a low initial thrombocyte count (<180,000/microl) are independent risk factors of thrombocytopenia. The risk of bleeding is higher with this form of thrombocytopenia not only due to the low thrombocyte count but also to the impaired function of the remaining thrombocytes. It is important to closely monitor platelet count during GP IIb/IIIa antagonist treatment. Platelet count monitoring two, six, twelve and 24 hour after starting the treatment reveals most cases of acute thrombocytopenia. Side effects can be avoided by the early discontinuation of the GP IIb/IIIa antagonist treatment. This article reviews the diagnosis and treatment of glycoprotein IIb/IIIa inhibitor-induced thrombocytopenia and summarizes the differential diagnosis from heparin-induced thrombocytopenia and laboratory-related pseudothrombocytopenia.