Idiosyncratic Drug-induced Agranulocytosis Research Articles

Involvement of Extracellular Vesicles in the Proinflammatory Response to Clozapine: Implications for Clozapine-Induced Agranulocytosis.

Most idiosyncratic drug reactions (IDRs) appear to be immune-mediated, but mechanistic events preceding severe reaction onset remain poorly defined. Damage-associated molecular patterns (DAMPs) may contribute to both innate and adaptive immune phases of IDRs, and changes in extracellular vesicle (EV) cargo have been detected post-exposure to several IDR-associated drugs. To explore the hypothesis that EVs are also a source of DAMPs in the induction of the immune response preceding drug-induced agranulocytosis, the proteome and immunogenicity of clozapine- (agranulocytosis-associated drug) and olanzapine- (non-agranulocytosis-associated drug) exposed EVs were compared in two preclinical models: THP-1 macrophages and Sprague-Dawley rats. Compared with olanzapine, clozapine induced a greater increase in the concentration of EVs enriched from both cell culture media and rat serum. Moreover, treatment of drug-naïve THP-1 cells with clozapine-exposed EVs induced an inflammasome-dependent response, supporting a potential role for EVs in immune activation. Proteomic and bioinformatic analyses demonstrated an increased number of differentially expressed proteins with clozapine that were enriched in pathways related to inflammation, myeloid cell chemotaxis, wounding, transforming growth factor-β signaling, and negative regulation of stimuli response. These data indicate that, although clozapine and olanzapine exposure both alter the protein cargo of EVs, clozapine-exposed EVs carry mediators that exhibit significantly greater immunogenicity. Ultimately, this supports the working hypothesis that drugs associated with a risk of IDRs induce cell stress, release of proinflammatory mediators, and early immune activation that precedes severe reaction onset. Further studies characterizing EVs may elucidate biomarkers that predict IDR risk during development of drug candidates. SIGNIFICANCE STATEMENT: This work demonstrates that clozapine, an idiosyncratic drug-induced agranulocytosis (IDIAG)-associated drug, but not olanzapine, a safer structural analogue, induces an acute proinflammatory response and increases extracellular vesicle (EV) release in two preclinical models. Moreover, clozapine-exposed EVs are more immunogenic, as measured by their ability to activate inflammasomes, and contain more differentially expressed proteins, highlighting a novel role for EVs during the early immune response to clozapine and enhancing our mechanistic understanding of IDIAG and other idiosyncratic reactions.

The Role of Myeloperoxidase in Clozapine-Induced Inflammation: A Mechanistic Update for Idiosyncratic Drug-Induced Agranulocytosis.

The risk of idiosyncratic drug-induced agranulocytosis (IDIAG) markedly constrains the use of clozapine, a neuroleptic with unparalleled efficacy. Most clozapine patients experience an early inflammatory response, likely a necessary step in IDIAG onset. However, most patients do not progress to IDIAG, presumably because of the requirement of specific human leukocyte antigen (HLA) haplotypes, T cell receptors, and other unknown factors. We established that clozapine activates inflammasomes and that myeloperoxidase bioactivation of clozapine generates neoantigens, but the connection between these early mechanistic events remained unknown and, thus, was the aim of this work. We found that the myeloperoxidase inhibitor PF-1355 attenuated myeloperoxidase activity in phorbol myristate acetate (PMA)-differentiated THP-1 macrophages, and it also attenuated clozapine-induced release of inflammatory mediators (e.g., IL-1β, CXCL1, and C-reactive protein). In vivo, pretreatment of Sprague Dawley rats with PF-1355 significantly attenuated clozapine-induced increases in neutrophil mobilization from the bone marrow to the blood and spleen, as determined using differential blood counts and flow cytometry. Moreover, the clozapine-triggered release of inflammatory mediators (e.g., IL-1β, calprotectin, CXCL1, and α-1-acid glycoprotein) from the liver, spleen, and bone marrow was dampened by myeloperoxidase inhibition. These data support the working hypothesis that oxidation of clozapine to a reactive metabolite by myeloperoxidase is critical for induction of the inflammatory response to clozapine. Ultimately, a better mechanistic understanding of the early events involved in the immune response to clozapine may elucidate ways to prevent IDIAG, enabling safer, more frequent therapeutic use of this and potentially other highly efficacious drugs.

Clozapine Induces an Acute Proinflammatory Response That Is Attenuated by Inhibition of Inflammasome Signaling: Implications for Idiosyncratic Drug-Induced Agranulocytosis.

Although clozapine is a highly efficacious schizophrenia treatment, it is under-prescribed due to the risk of idiosyncratic drug-induced agranulocytosis (IDIAG). Clinical data indicate that most patients starting clozapine experience a transient immune response early in treatment and a similar response has been observed in clozapine-treated rats, but the mechanism by which clozapine triggers this transient inflammation remains unclear. Therefore, the aim of this study was to characterize the role of inflammasome activation during the early immune response to clozapine using in vitro and in vivo models. In both differentiated and nondifferentiated human monocytic THP-1 cells, clozapine, but not its structural analogues fluperlapine and olanzapine, caused inflammasome-dependent caspase-1 activation and IL-1β release that was inhibited using the caspase-1 inhibitor yVAD-cmk. In Sprague Dawley rats, a single dose of clozapine caused an increase in circulating neutrophils and a decrease in lymphocytes within hours of drug administration along with transient spikes in the proinflammatory mediators IL-1β, CXCL1, and TNF-α in the blood, spleen, and bone marrow. Blockade of inflammasome signaling using the caspase-1 inhibitor VX-765 or the IL-1 receptor antagonist anakinra attenuated this inflammatory response. These data indicate that caspase-1-dependent IL-1β production is fundamental for the induction of the early immune response to clozapine and, furthermore, support the general hypothesis that inflammasome activation is a common mechanism by which drugs associated with the risk of idiosyncratic reactions trigger early immune system activation. Ultimately, inhibition of inflammasome signaling may reduce the risk of IDIAG, enabling safer, more frequent use of clozapine in patients.

Idiosyncratic Drug-Induced Neutropenia and Agranulocytosis in Elderly Patients.

Agranulocytosis is a rare, but serious and life-threatening hematologic disorder in elderly patients. Idiosyncratic drug-induced agranulocytosis (IDIA) has been classically defined by a neutrophil count below 0.5 × 109/L. The annual incidence of IDIA in Europe is about 1.6–9.2 cases per million inhabitants. Increasing age and female sex have been considered as risk factors for the development of this condition. Besides, it is well known that older people take on average more drugs than younger people. This condition is most often associated with the intake of antibacterial agents, antiplatelets, antithyroids, antipsychotics, antiepileptics and nonsteroidal anti-inflammatory drugs (NSAIDs). Initially, agranulocytosis may present without symptoms, but may quickly progress to a severe infection and sepsis. The causative drug should be immediately stopped. In febrile patients, blood cultures and where indicated, site-specific cultures should be obtained and early treatment with empirical broad-spectrum antibiotics started. Even with adequate treatment, the mortality rate is higher in elderly patients reaching up to 20%. Hematopoietic growth factors have proven to be useful as they shorten the duration of neutropenia. However, data on neutropenia and agranulocytosis in the elderly meeting the criteria of evidence-based medicine are still poor in the literature. This review analyzes the results of our experience as well as other published studies of the universal literature.

Severe Neutropenia and Agranulocytosis Related to Antithyroid Drugs: A Study of 30 Cases Managed in A Single Reference Center.

Background: The most important series devoted to antithyroid drug-induced severe neutropenia and agranulocytosis are Japanese studies, almost specifically in relation to the intake of methimazole. The clinical data of 30 Caucasian patients followed up for antithyroid drug-induced neutropenia at a third-level hospital are reported. Methods: The data of 30 patients with idiosyncratic antithyroid drug-induced neutropenia and agranulocytosis from a cohort study on drug-induced neutropenia and agranulocytosis conducted at the University Hospital of Strasbourg (France) were retrospectively reviewed. Results: The mean patient age was 61.7 years old (range: 20–87), and the gender ratio (F/M) was 4. Several comorbidities were reported in 23 patients (76.7%), with the mean Charlson comorbidity index of 1. The causative drugs were carbimazole and benzylthiouracil, in 28 (93.3%) and 2 cases, respectively, prescribed primarily for multi-hetero-nodular goiter or thyroid nodule to 18 patients (60%). Sore throat and acute tonsillitis (40%), isolated fever (20%), septicemia (13.3%), documented pneumonia (6.7%), and septic shock (6.7%) were the main clinical features upon admission. The mean neutrophil count at nadir was 0.02 and 0 × 109/L (range: 0–0.3). Regarding the patients’ hospital course: 13 cases (43.3%) worsened during hospitalization, severe sepsis was found in 26.7%, systemic inflammatory response syndrome—in 13.3%, and septic shock—in 3.3% of the cases, respectively. Broad-spectrum antibiotics were indicated for all the patients, and 21 (73.3%) of them received hematopoietic growth factors. Hematological recovery (neutrophil count ≥ 1.5 × 109/L) was seen at 8.3 days (range: 2–24), but faster in those receiving hematopoietic growth factors (4.9 days, p = 0.046). Two patients died during hospitalization, and the rest had a favorable clinical outcome. Conclusions: Antithyroid drug-induced neutropenia represents a serious complication resulting from the rates of severe infections especially in those cases severe neutropenia. In this setting, an established procedure for the management of patients seems useful or even indispensable in view of potential mortality.

Agranulocytoses médicamenteuses idiosyncrasiques : analyse de 7 ans dans un hôpital universitaire français

IntroductionIdiosyncratic drug-induced agranulocytosis is a rare but potentially serious haematological disorder. The pathophysiological mechanisms are complex and poorly understood. We aimed at investigating agranulocytosis drug related causes from the myelograms with “myeloid maturation arrest” performed in our university hospital over the last seven years. MethodsA retrospective analysis of myelograms collected for agranulocytosis was performed from 1st January 2010 to 31th December 2016. We used the method of Bégaud et al. for drug causality assessment. ResultsAmong the 104 myelograms analysed, 41 agranulocytosis were drug-induced, whose 28 were idiosyncratic. Among these 28 cases, 26 different drugs were involved. Agranulocytosis was a known adverse reaction in the summary of the product characteristics for 24 drugs, mainly associated with undetermined frequency (n=7). Mean onset latency was 38.1 days after starting the drug (calculated for n=23 cases) and granulocyte growth factors were used in 50% of cases without shortening the mean delay of blood count recovery. Bone marrow presented hypereosinophilia in 29% of cases. Pharmacovigilance reporting rate was 48%. ConclusionA “maturation arrest” in the myelogram is not pathognomonic for idiosyncratic drug-induced agranulocytosis. This rare event require multidisciplinary care involving haematologists, biologists and pharmacovigilance experts. Agranulocytosis reporting rate was high compared with usual adverse drug reaction reporting rate (5 to 10%), probably related to the potential severity of this event.

State of Art of Idiosyncratic Drug-Induced Neutropenia or Agranulocytosis, with a Focus on Biotherapies.

Introduction: Idiosyncratic drug-induced neutropenia and agranulocytosis is seldom discussed in the literature, especially for new drugs such as biotherapies outside the context of oncology. In the present paper, we report and discuss the clinical data and management of this relatively rare disorder, with a focus on biotherapies used in autoimmune and auto-inflammatory diseases. Materials and methods: A review of the literature was carried out using the PubMed database of the US National Library of Medicine. We searched for articles published between January 2010 and May 2019 using the following key words or associations: “drug-induced neutropenia”, “drug-induced agranulocytosis”, and “idiosyncratic agranulocytosis”. We included specific searches on several biotherapies used outside the context of oncology, including: tumor necrosis factor (TNF)-alpha inhibitors, anti-CD20 agents, anti-C52 agents, interleukin (IL) 6 inhibitors, IL 1 inhibitors, and B-cell activating factor inhibitor. Results: Idiosyncratic neutropenia remains a potentially serious adverse event due to the frequency of severe sepsis with severe deep tissue infections (e.g., pneumonia), septicemia, and septic shock in approximately two-thirds of all hospitalized patients with grade 3 or 4 neutropenia (neutrophil count (NC) ≤ 0.5 × 109/L and ≤ 0.1 × 109/L, respectively). Over the last 20 years, several drugs have been strongly associated with the occurrence of idiosyncratic neutropenia, including antithyroid drugs, ticlopidine, clozapine, sulfasalazine, antibiotics such as trimethoprim-sulfamethoxazole, and deferiprone. Transient grade 1–2 neutropenia (absolute blood NC between 1.5 and 0.5 × 109/L) related to biotherapy is relatively common with these drugs. An approximate 10% prevalence of such neutropenia has been reported with several of these biotherapies (e.g., TNF-alpha inhibitors, IL6 inhibitors, and anti-CD52 agents). Grade 3–4 neutropenia or agranulocytosis and clinical manifestations related to sepsis are less common, with only a few case reports to date for most biotherapies. Special mention should be made of late onset and potentially severe neutropenia, especially following anti-CD52 agent therapy. During drug therapy, several prognostic factors have been identified that may be helpful when identifying ‘susceptible’ patients. Older age (>65 years), septicemia or shock, renal failure, and a neutrophil count ≤0.1 × 109/L have been identified as poor prognostic factors. Idiosyncratic neutropenia should be managed depending on clinical severity, with permanent/transient discontinuation or a lower dose of the drug, switching from one drug to another of the same or another class, broad-spectrum antibiotics in cases of sepsis, and hematopoietic growth factors (particularly G-CSF). Conclusion: Significant progress has been made in recent years in the field of idiosyncratic drug-induced neutropenia, leading to an improvement in their prognosis (currently, mortality rate between 5 and 10%). Clinicians must continue their efforts to improve their knowledge of these adverse events with new drugs as biotherapies.

Idiosyncratic drug-induced neutropenia & agranulocytosis.

Few data is currently available on neutropenia and agranulocytosis related to drug intake. We report here data on 203 patients with established idiosyncratic drug-induced agranulocytosis, followed up in a referral centre within a university hospital. Data from 203 patients with idiosyncratic drug-induced agranulocytosis were retrospectively reviewed. All cases were extracted from a cohort study on agranulocytosis in the Strasbourg University Hospital (Strasbourg, France) RESULTS: : The mean age was 61.6 years old (range: 18-95), the gender ratio (F/M) was 1.3. Several comorbidities were present in 63.5%. The most frequent causative drugs were: antibiotics (49.3%), especially ß-lactams and cotrimoxazole; antithyroid drugs (16.7%); neuroleptic and anti-epileptic agents (11.8%); antiviral agents (7.9%); and platelet aggregation inhibitors as ticlopidine and acid acetylsalicylic (6.9%). The main primary clinical manifestations during hospitalization included: isolated fever (26.3%); septicaemia (13.9%); documented pneumonia (13.4%); sore throat and acute tonsillitis (9.3%); and septic shock (6.7%). The mean neutrophil count at nadir was 0.148 x 109/L (range: 0-0.48). All febrile patients were treated with broad-spectrum antibiotics and 107 (52.7%) with hematopoietic growth factors. The mean duration of haematological recovery (neutrophil count ≥1.5 x 109/L) was 7.8 (range: 2-20). This mean duration was reduced to 2.1 days (range: 2-16) (p = 0.057) with hematopoietic growth factors. Outcome was favourable in 91.6% of patients; seventeen died. Thirty-seven patients (18.2%) required intensive care. The present study demonstrated that idiosyncratic drug-induced agranulocytosis is a relative rare events; that antibiotics, antithyroid, neuroleptic and anti-epileptic agents, and platelet aggregation inhibitors are the main incriminated drug classes; that agranulocytosis typically serious, with at least 50% exhibiting severe sepsis and a mortality rate <10%; and that modern management of such disorder may reduce the infection-related mortality.

Idiosyncratic Drug-Induced Severe Neutropenia and Agranulocytosis in Elderly Patients (≥75years): A Monocentric Cohort Study of 61 Cases.

BackgroundLittle data is currently available in the literature on neutropenia and agranulocytosis in the elderly, and, to our knowledge, idiosyncratic drug-induced agranulocytosis is particularly poorly covered, or not at all.ObjectiveWe herein describe the clinical picture and outcome of patients aged ≥75 years with established idiosyncratic drug-induced agranulocytosis.Patients and MethodsData from 61 patients over 75 years old with idiosyncratic drug-induced agranulocytosis were retrospectively reviewed. All cases were extracted from a cohort study on agranulocytosis (n = 203) in the Strasbourg University Hospitals (Strasbourg, France), a referral center.ResultsThe mean age was 84.9 years (range 75–95), the gender ratio (F/M) was 2.4. Underlying diseases were present in 74 %. The most frequent causative drugs were antibiotics (43.8 %), antithyroid drugs (15.8 %), neuroleptic and anti-epileptic agents (12.3 %), and antiaggregant platelet agents (10.5 %). The primary clinical features during hospitalization included isolated fever (27.6 %), septicemia or septic shock (24.1 %), and pneumonia (20.7 %). The mean neutrophil count at nadir was 0.15 × 109/L (range 0–0.4). All febrile patients were treated with broad-spectrum antibiotics and 36 with hematopoietic growth factors. Outcome was favorable in 85.3 % of patients; nine patients died. Two elderly patients (3.3 %) died of uncontrolled septic shock relating to the depth of the neutropenia. Comparison of mortality between <75- and ≥75-year-old patients revealed a statistical difference: 4.2 % versus 14.8 % (p = 0.023).ConclusionsOur study demonstrates that 30 % of idiosyncratic drug-induced agranulocytosis concerned elderly patients. Antibiotic, antithyroid, neuroleptic, anti-epileptic, and antiaggregant platelet agents are the primary causative drug classes. Idiosyncratic drug-induced agranulocytosis is typically serious in this frail population of elderly patients, with at least 50 % suffering from severe sepsis and with a mortality rate of approximately 15 %. Modern management of agranulocytosis may reduce the infection-related mortality (3.3 %).

Exploring an animal model of amodiaquine-induced liver injury in rats and mice

Amodiaquine (AQ) is associated with a relatively high incidence of idiosyncratic drug-induced liver injury (IDILI) and agranulocytosis. A previous study reported that a combination of high dose AQ and glutathione (GSH) depletion led to liver injury. However, the characteristics of this toxicity were very different from AQ-induced liver injury in humans. We developed a model of AQ-induced liver injury with characteristics similar to the injury in humans by treating mice with lower doses of AQ for several weeks. In this study we found that not only did GSH depletion not increase AQ covalent binding to hepatic proteins at this lower dose, but also it paradoxically prevented the liver injury. We extended the model to rats and found AQ treatment led to a mild delayed onset liver injury that resolved despite continued treatment with AQ. Immunohistochemistry indicated the presence of Kupffer cell activation, apoptosis and hepatocyte proliferation in the liver. There was also an increase in serum IL-2, IL-5, IL-9, IL-12, MCP-1 and TGFβ, but a decrease in leptin. Coincident with the elevated serum ALT, the number of liver CD4+ T-cells, IL-17 secreting cells and TH17/Treg cells increased at Week 3 and decreased during continued treatment. Increases in NK1.1+ cells and activated M2 macrophages were also observed during liver injury. These results suggest that the outcome of the liver injury was determined by the balance between effector and regulatory cells. Co-treatment with cyclosporin prevented AQ-induced liver injury, which supports an immune mechanism. Retinoic acid (RA), which has been reported to enhance natural killer (NK) cell activity, exacerbated AQ-induced liver injury. These results suggest that AQ-induced IDILI is immune mediated and the subsequent adaptation appears to represent immune tolerance.

Clinical Articularities of Drug-induced Agranulocytosis or Severe Neutropenia in Elderly Patients

Agranulocytosis is a life-threatening disorder in any age and also in the elderly subjects who are receiving on the average a larger number of drugs than younger subjects. This disorder frequently occurs as an adverse reaction to drugs, particularly to antibiotics, antiplatelet agents, anti-thyroid drugs, neuroleptics or anti-epileptic agents and nonsteroidal anti-inflammatory agents. Although patients experiencing drug-induced agranulocytosis may initially be asymptomatic, the severity of the neutropenia usually translates into the onset of severe sepsis that requires intravenous broad-spectrum anti-biotherapy. In this setting, hematopoietic growth factors have been shown to shorten the duration of neutropenia. Thus with appropriate management, the mortality rate of idiosyncratic druginduced agranulocytosis is now of 5% to 10%. Today, drug-induced agranulocytosis still remains a rare event with an annual incidence from 3 to 12 cases per million of people. However, given the increased life expectancy and subsequent longer exposure to drugs, as well as the development of new agents, physicians should be aware of this complication and its management.

Development of a novel mouse model of amodiaquine-induced liver injury with a delayed onset

Amodiaquine (AQ) treatment is associated with a high incidence of idiosyncratic drug-induced liver injury (IDILI) and agranulocytosis. Evidence suggests that AQ-induced IDILI is immune mediated. A significant impediment to mechanistic studies of IDILI is the lack of valid animal models. This study reports the first animal model of IDILI with characteristics similar to mild IDILI in humans. Treatment of female C57BL/6 mice with AQ led to liver injury with delayed onset, which resolved despite continued treatment. Covalent binding of AQ was detected in the liver, which was greater in female than in male mice, and higher in the liver than in other organs. Covalent binding in the liver was maximal by Day 3, which did not explain the delayed onset of alanine aminotransferase (ALT) elevation. However, coincident with the elevated serum ALT, infiltration of liver and splenic mononuclear cells and activation of CD8 T-cells within the liver were identified. By Week 7, when ALT levels had returned close to normal, down-regulation of several inflammatory cytokines and up-regulation of PD-1 on T-cells suggested induction of immune tolerance. Treatment of Rag1−/− mice with AQ resulted in higher ALT activities than C57BL/6 mice, which suggested that the adaptive immune response was responsible for immune tolerance. In contrast, depletion of NK cells significantly attenuated the increase in ALT, which implied a role for NK cells in mild AQ-induced IDILI. This is the first example of a delayed-onset animal model of IDILI that appears to be immune-mediated.

Effect of Aminoglutethimide on Neutrophils in Rats: Implications for Idiosyncratic Drug-Induced Blood Dyscrasias

Aminoglutethimide (AMG) is an aromatic amine aromatase inhibitor associated with a high incidence of idiosyncratic blood dyscrasias, especially agranulocytosis. Animal models of idiosyncratic drug reactions (IDRs) represent essential tools to study these reactions; however, there is currently no valid model of idiosyncratic drug-induced agranulocytosis. Although AMG does not cause agranulocytosis in most animals or humans, drugs associated with serious IDRs generally cause a higher incidence of mild reactions that resolve despite continued treatment. Therefore, the effects of AMG on neutrophils and bone marrow in rats were studied to understand the mechanisms of more serious IDRs. An increase in peripheral blood neutrophils occurred as early as 24 h after AMG treatment with minimal changes to the total leukocyte count. Further investigation using 5-bromo-2'-deoxyuridine (BrdU) found an increased release of neutrophils from the bone marrow. Histologically, this corresponded to an increase in myeloid cells in the bone marrow, which was confirmed by differential staining with CD45 and CD71. AMG treatment stimulated an increase in colony forming unit granulocyte-macrophage and colony forming unit granulocyte ex vivo. There was also a marked increase in the number of activated neutrophils in the circulation expressing the extravasation marker CD62L. These findings indicate that AMG affects neutrophil production, release, and function. Similar effects on neutrophil kinetics in clozapine-treated rats have previously been found, and transient neutrophilia has been observed in patients taking other drugs associated with idiosyncratic agranulocytosis; therefore, the changes observed with AMG may be biomarkers to predict the risk that a drug will cause agranulocytosis.

Severe Neutropenia Following a Prolonged Course of Vancomycin That Progressed to Agranulocytosis with Drug Reexposure

To report a case of severe neutropenia after discontinuing prolonged treatment with vancomycin that progressed to agranulocytosis with vancomycin reexposure. A 78-year-old woman presented with severe neutropenia (absolute neutrophil count [ANC] 37 cells/μL) and hypocellular bone marrow with absence of myeloid elements 8 weeks after discontinuing a 3-week treatment course of vancomycin 750 mg every 12 hours. Filgrastim 300 μg daily was started for neutropenia and vancomycin 750 mg every 12 hours and aztreonam 1 g every 8 hours were initiated for catheter-related acute thrombophlebitis of the upper extremity. The patient's ANC decreased to 10 cells/μL within 3 days of starting vancomycin. We suspected an autoimmune process, potentially related to vancomycin exposure, and began treatment with methylprednisolone 1 mg/kg daily. The ANC precipitously dropped to 0 cells/μL despite treatment with steroids and an increased filgrastim dose of 480 μg/day. All antibiotics were discontinued on the fifth day of hospitalization. Within 48 hours, her neutrophil count showed recovery (white blood cell count 500 cells/μL; 10% neutrophils). Idiosyncratic drug-induced agranulocytosis is an uncommon phenomenon but is often associated with serious consequences such as sepsis. We believe this case is unique because of the unusually late neutropenia discovered several weeks after finishing a prolonged course of vancomycin. Furthermore, agranulocytosis developed after unintentional rechallenge with vancomycin. According to the Naranjo probability scale, this case illustrates a probable adverse event caused by vancomycin. This case demonstrates a serious adverse event potentially associated with vancomycin use, and calls attention to the safety of rechallenging with vancomycin during a possible drug-induced neutropenia.

Clinical presentation and management of drug-induced agranulocytosis

Objective: In this article, we report and discuss the clinical presentation and management of idiosyncratic drug-induced agranulocytosis (neutrophil count <0.5 × 109/l). Results/conclusions: Idiosyncratic drug-induced agranulocytosis remains a potentially serious adverse event owing to the frequency of severe sepsis with severe deep tissue infections (e.g., pneumonia), septicemia and septic shock in approximately two-thirds of all hospitalized patients. However, several prognostic factors have recently been identified that may be helpful in practice to identify ‘susceptible’ patients. Old age (>65 years), septicemia or shock, metabolic disorders such as renal failure and a neutrophil count below 0.1 × 109/l are currently consensually accepted as poor prognostic factors. In this potentially life-threatening disorder, modern management with broad-spectrum antibiotics and hematopoietic growth factors (particularly granulocyte colony-stimulating factor) is likely to improve prognosis. Thus, with appropriate management, the mortality rate from idiosyncratic drug-induced agranulocutosis is currently approximately 5%.

Effect of Clozapine on Neutrophil Kinetics in Rabbits

Clozapine is an atypical antipsychotic drug effective in the treatment of refractory schizophrenia; however, its use is limited due to its propensity to cause agranulocytosis in some patients. Little is known about the mechanism of idiosyncratic drug-induced agranulocytosis, in part because of the lack of a valid animal model. Clozapine is oxidized by activated human neutrophils and bone marrow cells to a reactive nitrenium ion by the myeloperoxidase-hydrogen peroxide system of neutrophils. This reactive metabolite has been shown in vitro to induce the apoptosis of neutrophils and bone marrow cells. While in vitro studies demonstrated the toxic potential of clozapine upon oxidation, it is not clear if similar conditions occur in vivo. In response to the difficulties encountered with detecting apoptotic neutrophils in vivo, we conducted a series of studies in rabbits using two fluorescent cell-labeling techniques to study the effect of clozapine treatment on neutrophil kinetics, that is, their rates of production and removal from circulation. The fluorescein dye, 5-(and-6)-carboxyfluorescein diacetate succinimidyl ester (CFSE), was used as a general cell label to measure the half-life of neutrophils in blood. In addition, the thymidine analogue, 5-bromo-2-deoxyuridine (BrdU), was used to label dividing cells, thus enabling the measurement of the efflux of neutrophils from the bone marrow. Clozapine, indeed, increased the rate of both the release of neutrophils from the bone marrow and their subsequent disappearance from circulation. Failure of the bone marrow to compensate for a shorter neutrophil half-life could lead to agranulocytosis. Alternatively, the damage to neutrophils caused by clozapine could, in some patients, lead to an immune-mediated response against neutrophils resulting in agranulocytosis.

Idiosyncratic Drug-Induced Agranulocytosis: The Paradigm of Deferiprone

Non chemotherapy drug-induced agranulocytosis is considered a potentially life-threatening idiosyncratic blood dyscrasia, thought to result from a partly elucidated immune and/or toxic damage on myelopoiesis, due to a multitude of drugs. Offending agents include clozapine, ticlopidine, antithyroid compounds, dipyrone, sulfasalzine, trimethropim/sulfomethoxazole, carmabazepine, and to a lesser extent, deferiprone (L1) and probably rituximab. Suspected drugs should be immediately stopped and, in symptomatic patients, once appropriate cultures have been obtained, broad-spectrum antibiotic treatment should be administered. Hematopoietic growth factors may be considered, specifically in patients with poor prognostic factors. Due to improved intensive care treatment and alertness of physicians the case fatality of the disorder has recently been decreased to 5%.

Agranulocytoses médicamenteuses idiosyncrasiques

Idiosyncratic drug-induced agranulocytosis is a potential adverse event of most drugs, rare but life-threatening. Its annual incidence does not exceed 10 cases per million population in Europe and has remained stable over the past two decades. Its pathogenesis is poorly understood. The principal drugs associated with it are antithyroid drugs, antibiotics including trimethoprim, sulfamethoxazole, and beta-lactamines, ticlopidine, sulfasalazine and dipyrone. Clinical presentation is highly variable but a severe infection is observed in more than one third of cases. Poor prognostic factors include a neutrophil count under 100/mm(3), age > 65 years, septicemia or shock, and severe comorbidity. Improvement in the management of infectious complications and the use of hematopoietic growth factors in severe cases helps explain that mortality rate has fallen to less than 5%.

Recognition and management of drug-induced blood cytopenias: the example of drug-induced acute neutropenia and agranulocytosis

Background: More than several hundred drugs, toxins, and herbs have been reported to cause blood abnormalities, and drugs account for 20 – 40% of all instances of cytopenias. Objective: In the present paper, we report and discuss the recognition and the management of drug-induced acute neutropenia or agranulocytosis (neutrophil count of < 0.5 × 109/l). Methods: A bibliographic search was performed on the PubMed database of the US National Library of Medicine for articles published from January 1990 to January 2008. Additional not published data of our cohort of drug-induced agranulocytosis in the University Hospital of Strasbourg, France were incorporated in this review. Results/conclusions: Idiosyncratic drug-induced acute neutropenia or agranulocytosis is a serious adverse event due to the frequency of severe infections (such as deep infections, septicemia and septic shock) but modern management with broad spectrum antibiotics and hematopoietic growth factors is likely to improve the prognosis. Given the increased life expectancy, increasing use of medications as a therapeutic modality and subsequent longer exposure to drugs, as well as the development of new agents, healthcare professionals should be aware of this adverse event and its management.

Idiosyncratic drug-induced agranulocytosis or acute neutropenia

Idiosyncratic drug-induced agranulocytosis or acute neutropenia is an adverse event resulting in a neutrophil count of under 0.5 x 10/l. Patients with such severe neutropenia are likely to experience life-threatening and sometimes fatal infections. Over the last 20 years, the incidence of idiosyncratic drug-induced agranulocytosis or acute neutropenia has remained stable at 2.4-15.4 cases per million, despite the emergence of new causative drugs: antibiotics (beta-lactam and cotrimoxazole), antiplatelet agents (ticlopidine), antithyroid drugs, sulfasalazine, neuroleptics (clozapine), antiepileptic agents (carbamazepine), nonsteroidal anti-inflammatory agents and dipyrone. Drug-induced agranulocytosis remains a serious adverse event due to the occurrence of severe sepsis with severe deep infections (such as pneumonia), septicemia and septic shock in around two thirds of patients. In this setting, old age (>65 years), septicemia or shock, metabolic disorders such as renal failure, and a neutrophil count under 0.1 x 10/l are poor prognostic factors. Nevertheless with appropriate management using preestablished procedures, with intravenous broad-spectrum antibiotic therapy and hematopoietic growth factors, the mortality rate is currently around 5%. Given the increased life expectancy and subsequent longer exposure to drugs, as well as the development of new agents, healthcare professionals should be aware of this adverse event and its management.