Clozapine-Associated Agranulocytosis: A Systematic Review. Is It Really So Frighteningly Common?

BACKGROUND

Clozapine is a very effective therapeutic option for schizophrenic disorders that have been refractory to most other therapies. This extremely positive aspect clashes easily with an adverse effect of the drug that is deemed to be a very dangerous one: agranulocytosis. We asked whether the mandatory strict hematological follow-up prescribed in the black box warning of clozapine's label is proportioned to the actual incidence of agranulocytosis, considering that is the main reason that such a drug is often used only late in the treatment course.

METHODS

We carried out a systematic review of reports examining clozapine administration and agranulocytosis incidence. We specifically selected those where mild and moderate neutropenia was not used as a trigger to stop administration of clozapine, to better estimate the sheer incidence of agranulocytosis when clozapine was continued even with mild hematological effect, where detected. We used PubMed, MEDLINE, EMBASE, Cochrane, and ScienceDirect databases to identify clinical studies conducted between January 1975 and April 2023.

RESULTS

We included 14 studies, mostly retrospective ones, that examined the incidence of hematological adverse effects in patients using clozapine. A total of 2354 subjects were included. The mean age of the subjects was 33.5 years. The mean duration of observation of subjects who took clozapine was 800 days, with a mean daily dose of 319.5 mg per day. Of the 2354 subjects examined, we found that 11 of them experienced agranulocytosis (0.47%).

CONCLUSIONS

These results suggest the evidence of a lower incidence of agranulocytosis than previously estimated and are in line with more recent meta-analyses. We may therefore think that clinical practice may demand a revision of the approach that both psychiatrists and supervising organizations often take when talking about clozapine.

Detection of drug safety signal of drug-induced neutropenia and agranulocytosis in all-aged patients using electronic medical records

PURPOSE

We explored the adverse drug reaction signals of drug-induced neutropenia (DIN) and drug-induced agranulocytosis (DIA) in hospitalized patients and evaluated the novelty of these correlations.

METHOD

A two-step method was established to identify the relationship between drugs and DIN or DIA using 5-year electronic medical records (EMRs) obtained from 242 000 patients at Qilu Hospital of Shandong University. First, the drugs suspected to induce DIN or DIA were selected. The associations between suspected drugs and DIN or DIA were evaluated by a retrospective cohort study using unconditional logistic regression analysis and multiple linear regression model.

RESULTS

Twelve suspected drugs (vancomycin, meropenem, voriconazole, acyclovir, ganciclovir, fluconazole, oseltamivir, linezolid, compound borax solution, palonosetron, polyene phosphatidylcholine, and sulfamethoxazole) were associated with DIN, and six suspected drugs (vancomycin, voriconazole, acyclovir, ganciclovir, fluconazole, and oseltamivir) were associated with DIA. The multivariate linear regression model revealed that nine drugs (vancomycin, meropenem, voriconazole, ganciclovir, fluconazole, oseltamivir, compound borax solution, palonosetron, and polyene phosphatidylcholine) and four drugs (vancomycin, voriconazole, ganciclovir, and fluconazole) were found to be associated with DIN and DIA, respectively. While logistic regression analysis revealed that palonosetron and ganciclovir were associated with DIN and DIA, respectively.

CONCLUSION

Palonosetron and ganciclovir were found to be correlated with drug-induced granulocytopenia. The results of this study provide an early warning of drug safety signals for drug-induced granulocytopenia, facilitating a quick and appropriate response for clinicians.

No adverse events were observed in clozapine-treated patients on extended hematologic monitoring intervals during the coronavirus pandemic in four psychiatric centers in Japan

AIM

As an emergency measure during the coronavirus disease pandemic, the monitoring interval for clozapine use was temporarily extended beyond the regulatory requirement in Japan, which is the safest monitoring interval worldwide. In this study, we aimed to explore the effect of this measure on patients undergoing clozapine treatment.

METHODS

This retrospective chart review study included patients with treatment-resistant schizophrenia (TRS) who were undergoing clozapine treatment at four psychiatric institutions in Japan. Demographic characteristics and clinical information of these patients were collected on April 27, 2020, when Japanese psychiatrists were virtually allowed to prescribe clozapine beyond the regulatory requirement. Furthermore, information of adverse events related to the emergency measure was collected and analyzed.

RESULTS

Of the 41 patients with TRS included in this study, 19 patients underwent extended hematological monitoring during clozapine treatment. No psychiatric or hematological adverse events were observed in the patients during the extended monitoring interval.

CONCLUSION

This study suggested that there were few adverse events of clozapine-treated patients related to emergency measures in Japan. However, hematological monitoring intervals during clozapine treatment have been emergently extended worldwide; hence, it is necessary to verify the results of these measures.

Silent existence of eosinopenia in sepsis: a systematic review and meta-analysis

BACKGROUND

Sepsis is a life-threatening and time-critical medical emergency; therefore, the early diagnosis of sepsis is essential to timely treatment and favorable outcomes for patients susceptible to sepsis. Eosinopenia has been identified as a potential biomarker of sepsis in the past decade. However, its clinical application progress is slow and its recognition is low. Recent studies have again focused on the potential association between Eosinopenia and severe infections. This study analyzed the efficacy of Eosinopenia as a biomarker for diagnosis of sepsis and its correlation with pathophysiology of sepsis.

METHOD

The protocol for this meta-analysis is available in PROSPERO (CRD42020197664). We searched PubMed, EMBASE, Web of Science, and Cochrane Central Register of Controlled Trials CENTRAL databases to identify studies that met the inclusion criteria. Two authors performed data extraction independently. The pooled outcomes were calculated by TP (true positive), FP (false positive), FN (false negative), TN (true negative) by using bivariate meta-analysis model in STATA 14.0 software. Meanwhile, possible mechanisms of sepsis induced Eosinopenia was also analyzed.

RESULTS

Seven studies were included in the present study with a total number of 3842 subjects. The incidence of Eosinopenia based on the enrolled studies varied from 23.2 to 92.7%. For diagnosis of sepsis, the pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio and diagnostic odds ratio of Eosinopenia were 0.66 (95%CI [0.53-0.77]), 0.68 (95%CI [0.56-0.79]), 2.09 (95%CI [1.44-3.02]), 0.49 (95%CI [0.34-0.71]) and 4.23 (95%CI [2.15-8.31]), respectively. The area under the summary receiver operator characteristic curve (SROC) was 0.73 (95%CI [0.68-0.76]). Meta-regression analysis revealed that no single parameter accounted for the heterogeneity of pooled outcomes. For each subgroup of different eosinopenia cutoff values (50, 40, ≤25, 100), the sensitivity was 0.61, 0.79, 0.57, 0.54, and the specificity was 0.61, 0.75, 0.83, 0.51, respectively.

CONCLUSIONS

Our findings suggested that Eosinopenia has a high incidence in sepsis but has no superiority in comparison with conventional biomarkers for diagnosis of sepsis. However, eosinopenia can still be used in clinical diagnosis for sepsis as a simple, convenient, fast and inexpensive biomarker. Therefore, further large clinical trials are still needed to re-evaluate eosinopenia as a biomarker of sepsis.

Association of MICA gene polymorphisms with thionamide-induced agranulocytosis

BACKGROUND

Thionamide-induced agranulocytosis (TIA), namely antithyroid drug (ATD)-induced agranulocytosis, is one of the most feared adverse effect of ATDs. It is defined as a granulocyte count of less than 0.5 × 10⁹/L after ATD administration. Several studies reported that TIA is associated with human leukocyte antigen (HLA) and nearby genes. Our previous study found that the susceptibility genes of TIA are similar in north China and European populations.

METHODS

We evaluated the associations of 23 candidate single nucleotide polymorphisms (SNPs) in 37 patients with TIA and 254 patients with Graves' disease (GD) as controls by iPLEX MassARRAY system.

RESULTS

Five SNPs in the MHC class I polypeptide-related sequence A(MICA) genes [rs4349859 (p = 1.43E-7); rs145575084 (p = 5.79E-6); rs116135464 (p = 3.70E-5); rs148015908 (p = 3.79E-5) and rs189600525 (p = 2.15E-4)] were found to be significantly associated with TIA after Bonferroni correction. After combining with previous data of rs4349859 and HLA-B*27:05, the haplotype analysis showed that patients carrying P-A-C-A-T-T-A haplotype have a higher risk of TIA (p = 9.76E-7; OR = 14.85, 95% CI 3.63-60.77).

CONCLUSION

Our findings suggest that five high linked SNPs of MICA gene are significantly associated with susceptibility to TIA.

Clozapine-induced agranulocytosis in Japan: Changes in leukocyte/neutrophil counts before and after discontinuation of clozapine

OBJECTIVE

To determine the prevalence, background factors, and progression of and recovery from clozapine-induced agranulocytosis in Japan.

METHODS

Data on treatment-resistant schizophrenia patients registered with the Clozaril Patient Monitoring Service (CPMS) between July 29, 2009 and January 20, 2016 were extracted. Patients with a neutrophil count <500/mm³ were defined as having agranulocytosis, and those with a leukocyte count <3,000/mm³ or a neutrophil count <1,500/mm³ but not meeting the criteria for agranulocytosis were defined as having leukopenia/neutropenia.

RESULTS

Of 3,746 patients, agranulocytosis and leukopenia/neutropenia were observed in 38 (1.0%) and 182 (4.9%) patients, respectively. Age was significantly higher in the agranulocytosis group (p < .001). Decreased leukocyte counts 1 week prior to discontinuation were observed only in the agranulocytosis group. The median number of days to recovery from agranulocytosis and leukopenia/neutropenia was 10 and 4, respectively, with more variation in the latter.

CONCLUSIONS

Although some patients with leukopenia/neutropenia might carry less pathologic significance, the results of this study reconfirmed the importance of regular blood monitoring for preventing agranulocytosis.

The prevalence of agranulocytosis and related death in clozapine-treated patients: a comprehensive meta-analysis of observational studies

BACKGROUND

Clozapine treatment increases the risk of agranulocytosis, but findings on the epidemiology of agranulocytosis have been inconsistent. This meta-analysis examined the prevalence of agranulocytosis and related death in clozapine-treated patients.

METHODS

A literature search in the international (PubMed, PsycINFO, and EMBASE) and Chinese (WanFang, Chinese National Knowledge Infrastructure, and Sinomed) databases was conducted. Prevalence estimates of agranulocytosis and related death in clozapine-treated patients were synthesized with the Comprehensive Meta-Analysis program using the random-effects model.

RESULTS

Thirty-six studies with 260 948 clozapine-treated patients published between 1984 and 2018 were included in the meta-analysis. The overall prevalence of agranulocytosis and death caused by agranulocytosis were 0.4% (95% CI 0.3-0.6%) and 0.05% (95% CI 0.03-0.09%), respectively. The prevalence of agranulocytosis was moderated by sample size, study quality, year of publication, and that of data collection.

CONCLUSIONS

The prevalence of clozapine-associated agranulocytosis is low. Agranulocytosis-related death appears rare.

A Concise Review of Autoimmune Cytopenias in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is frequently associated with autoimmune complications such as autoimmune hemolytic anemia, immune thrombocytopenia, pure red cell aplasia, and autoimmune granulocytopenia. It is critical to diagnose cytopenias from these secondary complications of CLL accurately, since prognosis and therapy are substantially different from patients who have cytopenias due to extensive bone marrow infiltration by CLL. The pathogenesis of autoimmune cytopenias in CLL is complex; and it involves antigen presentation by CLL cells to polyclonal B cells resulting in production of autoantibody, and alteration of the T cell milieu tilting the balance in favor of an autoimmune response. Traditional therapy of autoimmune complications in CLL consists of immunosuppression with corticosteroids and/or anti-CD20 monoclonal antibodies. In patients who have a suboptimal response, treating the underlying CLL is generally effective in ameliorating secondary cytopenias. Although novel oral therapies such as ibrutinib, idelalisib, and venetoclax have been shown to be extremely effective in the management of CLL, prospective data from larger numbers of patients with longer follow-up are needed prior to recommending their routine use in the management of autoimmune cytopenias in CLL.

Analysis of 754 cases of antithyroid drug-induced agranulocytosis over 30 years in Japan

BACKGROUND

Agranulocytosis is a rare but serious complication of antithyroid drug (ATD) therapy. Characteristics of agranulocytosis have been reported in only a small number of patients.

METHOD

We studied 754 cases of ATD-induced agranulocytosis reported over 30 years. The age distribution and sex ratio were compared with those in 12 503 untreated Graves' patients at Kuma Hospital. The annual number of new Graves' patients in Japan was estimated from the Japan Medical Data Center Data Mart-Pharmacovigilance health insurance receipt database.

RESULTS

Agranulocytosis developed within 90 days after starting ATD therapy in most patients (84.5%). The methimazole dose given at onset was 25.2 ± 12.8 mg/d (mean ± SD). The mean age was 43.4 ± 15.2 years, and the male to female ratio was 1:6.3. When compared with patients at Kuma Hospital, patients with agranulocytosis were older (P < .001) and more females (P < .0001). Of 211 patients with more than 1 granulocyte measurement before onset, 131 (62%) showed normal counts (>1000/μL) within 2 weeks before onset, demonstrating real sudden onset of agranulocytosis. In contrast, some of the 20 patients with more than 4 measurements showed gradual decreases in granulocyte counts. Analysis of physician reports for 30 fatal cases revealed that some deaths might have been prevented. The number of new Graves' patients treated with ATD was estimated at about 35 000 per year, and the incidence rate of agranulocytosis was 0.1% to 0.15% in Japan.

CONCLUSION

This is the largest study of agranulocytosis. Agranulocytosis tends to occur abruptly within 3 months after initiation of ATD therapy, although it develops gradually in some patients. Providing every patient with sufficient information on agranulocytosis is critical.

Antithyroid drug-induced hematopoietic damage: a retrospective cohort study of agranulocytosis and pancytopenia involving 50,385 patients with Graves' disease

CONTEXT

Although antithyroid drug (ATD)-induced hematopoietic damage is a significant concern, it has not been comprehensively investigated.

OBJECTIVE

Our objective was to describe the clinical features of ATD-induced hematopoietic damage.

DESIGN AND SETTING

This was a retrospective cohort study in Tokyo, Japan.

PATIENTS

Between January 1983 and December 2002, 50,385 patients at Ito Hospital were diagnosed with Graves' disease. We retrospectively reviewed their medical, pathological, and laboratory records between January 1983 and December 2010.

MAIN OUTCOME

Incidence and clinical features of ATD-induced agranulocytosis and pancytopenia were evaluated.

RESULTS

Of 55 patients with documented hematopoietic damage, 50 had agranulocytosis and 5 had pancytopenia. All of them received ATD, either methimazole (n = 51) or propylthiouracil (n = 4). Median intervals between initiation of ATD therapy and the onset of agranulocytosis and pancytopenia were 69 d (range, 11-233 d) and 41 d (range, 32-97 d), respectively. Either anemia or thrombocytopenia was also documented in seven of the 50 patients with agranulocytosis. Agranulocytosis was the first manifestation of hematopoietic damage in four of the five patents with pancytopenia. Hematopoietic damage recovered with supportive measures including granulocyte colony-stimulating factor (n = 37), steroids (n = 10), and other supportive measures (n = 8) in 54 patients, whereas the remaining patient died of complications from infection. This study failed to identify the risk factors for ATD-induced hematopoietic damage.

CONCLUSIONS

This study showed that ATD cause hematopoietic changes, which are occasionally severe and potentially fatal. The pathogenesis of agranulocytosis and pancytopenia might overlap, and additional studies are warranted to clarify this and to establish an optimal treatment strategy.

[Retrospective study of clozapine use in Ile-de-France]

INTRODUCTION

Clozapine, synthesized in the sixties, is an atypical antipsychotic drug whose history has been marked by its haematological toxicity. The purpose of this study was, ten years after it had been replaced at French psychiatrists' disposal, to gather data on the prescription modalities of clozapine, assess whether some factors could affect its efficacy, and describe the population of schizophrenic patients concerned.

METHODOLOGY

Psychiatrists in the Paris region were asked to answer a questionnaire about their patients treated with clozapine. The information collected was about socio-demographic data, history of psychiatric disorder and the way clozapine was used. It was a retrospective study concerning 98 patients.

RESULTS

Subjects were 57 men and 41 women, with a mean age of 38 years. The majority of patients came from metropolitan France. Patients suffered from various clinical subtypes of schizophrenia, as assessed according to DSM IV criteria. Predominant symptomatology during lifetime was most often auditory hallucinations (41%). Mean duration of lifetime neuroleptic treatment was 10.3 years and breaks in follow-up were rare. Mean number of hospitalisations was 6.9 and a little less than half of the patients had been committed involuntarily. Lastly, 38% of patients had attempted suicide at least once and 35% had expressed hetero-agressive behavior. Main indication of clozapine was resistant schizophrenia (88.5% of patients) and mean duration of treatment was 2 years and 4 months. Treatment efficacy was assessed as good or medium in 77.9% of patients, at mean doses (322 mg per day) in keeping with data from the literature. Tolerance was considered on the whole as satisfactory by half of the clinicians. Among the 98 patients of the study, 21.6% had stopped taking clozapine. The reasons for withdrawal were: inefficacy (6.2%), granulopenia (5.2%), epilepsy (1%) and 8.2% for various reasons (half of these cases being non-compliance with treatment). The study of the 5 cases of granulopenia showed that 3 patients had another associated psychotropic medication: 1 patient received only clozapine as monotherapy, 1 data was missing. Two thirds of all patients were receiving another psychotropic drug in association with clozapine, mainly benzodiazepines (18.4%), antidepressants (15.3%) or mood stabilizers (7.1%). The "therapeutic efficacy" variable was compared with some variables in order to isolate factors possibly associated with a better efficacy of clozapine or, on the contrary, with a population of patients poorly responding to treatment. However, no statistically significant difference appeared according to the variables studied, such as gender or lifetime duration of neuroleptic treatment. Moreover, there was no statistically significant difference in efficacy according to schizophrenia subtype, main symptomatology during the course of illness or substance abuse. We studied whether any factor could affect the occurrence of granulopenia. No statistically significant difference was found. The mean age of patients having stopped the treatment because of granulopenia was higher than in the group with other reasons for interruption, but did not reach statistical significance. A trend also appeared towards female predominance (60% of women in the granulopenia group) and 3/4 of patients who had stopped their treatment because of agranulocytosis received another psychotropic drug in association with clozapine.

CONCLUSION

As expected, the main indication for prescribing clozapine was resistant schizophrenia, but contrary to data from the international literature, the efficacy profile was the same whatever the clinical subtype of schizophrenia. The tolerance to clozapine was considered on the whole as satisfactory, but the high proportion of granulopenias leading to treatment withdrawal (5.2% of patients) confirms the need to remain cautious and stresses the importance of regular haematological monitoring. Furthermore, the study of the prescription modalities of clozapine shows that contrary to the guidelines, clozapine is often associated with other psychotropic drugs. In this study, it is striking to note that 75% of granulopenias occurred in a coprescription situation.

Centers for Disease Control and Prevention (CDC). Agranulocytosis associated with cocaine use - four States, March 2008-November 2009

In April 2008, a clinical reference laboratory in New Mexico notified the New Mexico Department of Health (NMDOH) of a cluster of unexplained agranulocytosis cases confirmed by bone marrow histopathology during the preceding 2 months. NMDOH began an investigation, which identified cocaine use as a common exposure in 11 cases of otherwise unexplained agranulocytosis during April 2008-November 2009. In the midst of the NMDOH investigation, in November 2008, public health officials in British Columbia and Alberta, Canada, reported detecting levamisole (an antihelminthic drug used mainly in veterinary medicine and a known cause of agranulocytosis) from clinical specimens and drug paraphernalia of cocaine users with agranulocytosis. In January 2009, NMDOH posted a notification of its findings on CDC's Epidemic Information Exchange (Epi-X) and notified poison control centers. In a separate investigation during April--November 2009, public health officials in Seattle, Washington, identified 10 cases of agranulocytosis among persons with a history of cocaine use. Of the 21 cases, levamisole was detected from clinical specimens in four of the five patients tested. According to the Drug Enforcement Administration (DEA), as of July 2009, 69% of seized cocaine lots coming into the United States contained levamisole as an added agent. This report summarizes the investigations in New Mexico and Washington, which suggested that levamisole in cocaine was the likely cause of the agranulocytosis. Health-care providers should consider these findings in the differential diagnosis of agranulocytosis, and public health officials should be aware of cases of agranulocytosis associated with cocaine use.

Methimazole-induced agranulocytosis in patients with Graves' disease is more frequent with an initial dose of 30 mg daily than with 15 mg daily

BACKGROUND

Antithyroid drugs (ATDs) are prescribed as the initial therapy for the majority of patients with Graves' disease in many areas of the world. Although, it is well known that agranulocytosis is one of the most serious side effects of ATDs, there has not yet been any conclusive evidence that the prevalence of agranulocytosis induced by ATDs is dose related. This study was performed to determine if the prevalence of agranulocytosis is different depending on the starting dosage of ATDs in patients with Graves' disease.

METHODS

Until 1996, we had typically prescribed 30 mg/d of methimazole (MMI) as the initial dosage for the treatment of Graves' disease at our institution. We changed the initial MMI dosage to 15 mg/d as a general rule in 1997. As a consequence, we acquired two groups of patients with Graves' disease who received different dosages of MMI. We retrospectively compared the prevalence of MMI-induced agranulocytosis in patients who received 15 mg/d of MMI to those who received 30 mg/d of MMI.

RESULTS

There were 2087 subjects treated with 30 mg/d of MMI and 2739 treated with 15 mg/d of MMI. The prevalence of agranulocytosis in the 30 mg/d group was significantly higher than in the 15 mg/d group (0.814% vs. 0.219%, respectively, p < 0.01). The prevalence of agranulocytosis plus neutropenia in the 30 mg/d group was also significantly higher than in the 15 mg/d group (1.581% vs. 0.474%, respectively, p < 0.001).

CONCLUSIONS

It is very likely that MMI-induced agranulocytosis occurs with a larger dosage of MMI and is dose related. Considering both the effectiveness and the risk of serious side effects, we recommend 15 mg/d of MMI as the starting dosage for the treatment of Graves' disease.

Drug-related blood dyscrasias in a Swedish reporting system, 1985-1994

Drug-related blood dyscrasias as reported in Sweden during a 10-yr period have been analysed in relation to sales and prescription data. The number of cases reported were as follows: agranulocytosis 390, thrombocytopenia 391, pancytopenia 50 and aplastic anaemia 36. The annual incidence rates per 10(6) inhabitants were: agranulocytosis 4.8, thrombocytopenia 5.6, pancytopenia 1.1 and aplastic anaemia 0.5. Incidences in the elderly were higher for all dyscrasias except aplastic anaemia. The most commonly reported drugs for all dyscrasias were sulphonamides and diuretics, but when related to sales data the risk of agranulocytosis was high for clozapine, dapsone, mianserin and sulphasalazine, while the risk did not seem to be increased for furosemide. For thrombocytopenia, furosemide, co-trimoxazole and the measles, mumps and rubella vaccine were most commonly reported. The risk for pancytopenia and aplastic anaemia was increased for acetazolamide and co-trimoxazole. As spontaneous reporting systems are primarily set up for signalling purposes, such data must always be interpreted with utmost care.

Drugs in the aetiology of agranulocytosis and aplastic anaemia

Agranulocytosis and aplastic anaemia are rare but serious conditions known to be caused by numerous drugs. Most of what is known or suspected about the aetiology is based on case reports, with only a few formal epidemiological studies that provide quantitative estimates of risk. Updated results have been obtained from a combined analysis of data from 3 case-control studies that used similar methods: the International Agranulocytosis and Aplastic Anemia Study (IAAAS), conducted in Israel and Europe; a study conducted in the northeast US; and a study conducted in Thailand. Totals of 362 cases of agranulocytosis, 454 cases of aplastic anaemia and 6458 controls were included in the analyses. The IAAAS and Thai study were population-based, providing estimates of the incidence of the 2 dyscrasias. The overall annual incidence of agranulocytosis in the ambulatory population was 3.4/10(6) in the IAAAS and 0.8/10(6) in Thailand; by contrast the incidence of aplastic anaemia was 2.0/10(6) in the IAAAS and 4.1/10(6) in Thailand. A total of 21 compounds were significantly associated with an increased risk of agranulocytosis in the IAAAS and US studies. Excess risks ranged from 0.06 to 13 cases/10(6) users/wk; the most strongly associated drugs were procainamide, anti-thyroid drugs and sulphasalazine. An association with drugs that had previously been suspected was also seen in Thailand. The overall aetiologic fractions of agranulocytosis due to drug use were 62% in the IAAAS, 72% in the US and 70% in Thailand. Eleven drugs were significantly associated with an increased risk of aplastic anaemia, with excess risks ranging from 1.4 to 60 cases/10(6) users in a 5-month period. The most strongly associated drugs were penicillamine, gold and carbamazepine. Aetiologic fractions were 27% in the IAAAS, 17% in the US and 2% in Thailand, which paralleled the prevalence of use of associated drugs in the 3 populations. The present results confirm that agranulocytosis is largely a drug-induced disease, with similar proportions accounted for in 3 disparate geographic regions. By contrast, although many of the expected associations were observed for aplastic anaemia, most of the aetiology is not explained by drugs. For all associated drugs, the excess risks are sufficiently low that blood dyscrasias should not figure prominently in the balancing of risks and benefits.

Incidence and cause of aplastic anemia, hemolytic anemia, agranulocytosis and thrombocytopenia

A total of 745 patients with cytopenia (aplastic anemia 157, hemolytic anemia 101, agranulocytosis 136, thrombocytopenia 351) were diagnosed during a 5-year period in a health care region comprising 16% of the Swedish population. The total incidence was for aplastic anemia 24.6, hemolytic anemia 15.8, agranulocytosis 21.3 and thrombocytopenia 55.0 cases per 10(6) and year. Compared to 10 years earlier, aplastic anemia and agranulocytosis have become more common, thrombocytopenia occurs with unchanged frequency while hemolytic anemia is rarer. The overall incidence is 5 times higher in elderly (greater than 65 y.) than in younger patients and 1.3 times higher in women than in men, figures that make total incidence figures rather meaningless. The most common cause is "unknown" (45%), the next drug-induced (25-36% including cytostatic drugs). Disregarding cytostatics, the drugs most often encountered are oral diuretics, analgesics, antiphlogistics and sulfonamides.

Clozapine underutilization and discontinuation in African Americans due to leucopenia

Clozapine use has been notably lower in African American patients than in Caucasians. It has been suggested that lower normal ranges for white blood cell (WBC) counts in African Americans, known as benign ethnic neutropenia, may account partially for the disparity. We examined the rates of leucopenia and agranulocytosis as reasons for discontinuation of clozapine in a sample of 1875 patients with schizophrenia treated in the State of Maryland. Between 1989 and 1999, 5.3% (31/588) of African Americans and 2.4% (31/1287) of Caucasians discontinued clozapine treatment due to leucopenia (chi square = 10.35, df = 1, P = 0.001). No African American patients developed agranulocytosis while 8 Caucasian patients (0.62%) developed this blood dyscrasia. Discontinuations due to leucopenia occurred throughout treatment. Discontinuations due to agranulocytosis occurred primarily in the first 18 weeks (7/8; 87.5% patients with agranulocytosis). It is likely that African Americans had clozapine discontinued unnecessarily due to benign ethnic neutropenia. We concur with recent recommendations to acknowledge differences in WBC values in African Americans and to modify prescribing guidelines or formally acknowledge benign ethnic leucopenia like in other countries in order to facilitate greater use of clozapine in these patients.

Non-chemotherapy drug-induced agranulocytosis

Acute agranulocytosis is a rare, potentially life-threatening condition, which is attributable to drugs in > 70% of cases. Agranulocytosis is characterised by a peripheral neutrophil count < 0.5 x 10(9)/l. It often manifests with a severe sore throat, but isolated fever, pneumonia or septicaemia are not uncommon. Agranulocytosis may be caused by many drugs. High-risk drugs include antithyroid drugs, clozapine, ticlopidine, sulfasalazine, dipyrone, trimethoprim/sulfamethoxazole, carbamazepine and probably rituximab. Suspect drugs should be stopped immediately. In febrile patients, blood cultures and, where indicated, site-specific cultures should be obtained and treatment with empirical broad spectrum antibiotics started. Haematopoietic growth factors should be considered in patients with poor prognostic factors (e.g., a neutrophil count < 0.1 x 10(9)/l), severe clinical infection or severe underlying disease or comorbidity. Case fatality has decreased to ~ 5% in recent years, probably owing to improved intensive care treatment and increased alertness of physicians to this severe adverse reaction.

The relation of initial methimazole dose to the incidence of methimazole-induced agranulocytosis in patients with Graves' disease

The relation between the incidence of methimazole (methylmercaptoimidazole; MMI)-induced agranulocytosis and initial MMI dose was evaluated in a group of 514 patients with Graves' disease who were treated between 1995 and 2005. One hundred and forty-six (28.40%) patients had received an initial dose of 30 mg MMI and 277 (53.89%) patients had been treated with 15 mg MMI. Nine patients (1.75%) developed agranulocytosis due to MMI treatment. Six (4.11%) of 146 patients who received an initial dose of 30 mg MMI, two (4.54%) of 44 patients given an initial dose of 20 mg MMI, and one (0.36%) of 277 patients given an initial dose of 15 mg MMI developed agranulocytosis. There was a statistically significant difference in agranulocytosis incidence between patients receiving an initial dose of 30 mg MMI and those who received an initial dose of 15 mg. Although 8 (4.10%) of 195 patients in the high-dose group (20 mg or higher) developed agranulocytosis, only 1 (0.31%) of 319 patients in the low-dose group (15 mg or lower) did. In conclusion, the incidence of agranulocytosis with low-dose MMI therapy was ten times lower than that of the high-dose regimen.

Detection and incidence of drug-induced agranulocytosis in hospital: a prospective analysis from laboratory signals

AIMS

Our objectives were to assess the detection and incidence of drug-induced agranulocytosis in two university hospitals using hematology laboratory data.

METHODS

A prospective study was undertaken at Toulouse University Hospital (France) and Navarra University Hospital (Spain) for 1 year (from 1 May 2004 to 30 April 2005). Using a computerized process and hematology laboratory data, all neutrophil counts with a value less than 500/mm(3) were registered, allowing identification of inpatients suffering from agranulocytosis during the period of the study. Medical records of all selected patients were then consulted. Cytostatic drugs were excluded from this study.

RESULTS

During the period of the study, 225,659 neutrophil counts were performed in both hospitals, of which 2,835 (1.26%) had a neutrophil count less than 500/mm(3), corresponding to 739 patients. Seventeen patients were excluded because of lack of data, and 20 cases of infants younger than 3 months were excluded. Among the remaining patients (n = 702), 23 cases of drug-induced agranulocytosis (excluding cytostatic drugs) were suspected. All cases were classified as "serious" since they led to death in 2 cases, hospitalization or prolongation of hospitalization in 19 cases and threatening of vital prognosis in 2 cases. Withdrawal of suspected drugs was done in all cases with regression of neutropenia in 21 cases. According to hospitalization data, the annual incidence of drug-induced agranulocytosis was 1.62 (1.0-2.6) per 10,000 inpatients in Toulouse University hospital (based on 534 cases) and 3.24 (0.9-8.3) per 10,000 inpatients in Navarra University Hospital (based on 168 cases). The involved drugs were mainly antibacterial (30.4%), immunosuppressive (17.4%), antithyroid (13.0%), antiplatelet (8.7%) and nonsteroidal anti-inflammatory (8.7%) ones. Only seven cases from Toulouse University Hospital were spontaneously reported by physicians during the same period. Thus, the underreporting coefficient (U) was 2.71 (63.2%) in France.

CONCLUSION

Our survey allowed us to identify the suspected drug-induced agranulocytosis through a prospective study in a large sample of inpatients using only laboratory data analysis. We also note an important underreporting rate of this serious adverse drug reaction (ADR) to the official French pharmacovigilance system. Laboratory data analysis could be used for identifying serious ADRs.

Long-term patient monitoring for clozapine-induced agranulocytosis and neutropenia in Korea: when is it safe to discontinue CPMS?

OBJECTIVES

This study documents the incidences of agranulocytosis and neutropenia, and the patterns of incidence of the side effects of long-term clozapine treatment in order to determine an appropriate time to stop the Clozaril Patient Monitoring System (CPMS).

METHODS

Hematological, demographic, and other data from the CPMS for 6782 patients who took clozapine for the past 11 years in the Republic of Korea has been analyzed.

RESULTS

Twenty-nine (53.7%) of fifty-four agranulocytosis cases occurred within the first 18 weeks. The cumulative incidence of agranulocytosis was 1.64% between 6 and 11 years and the crude incidence was 0.8%. Neutropenia occurred in 697 patients, and 365 (52.4%) of these cases occurred within the first 18 weeks. The cumulative incidence of neutropenia was 19.8% between 8 and 11 years, and the crude incidence was 10.3%. There were no cases of agranulocytosis or neutropenia after the 9th year of clozapine treatment.

CONCLUSIONS

The incidence of agranulocytosis in the Republic of Korea was similar to those in the rest of the world. While agranulocytosis began several years after clozapine treatment, long-term monitoring of white blood cells is necessary. We suggest that the CPMS should be stopped or less frequently after the 9th year of treatment.

Evaluation of an interchangeability switch in patients treated with clozapine: A retrospective review

OBJECTIVE

To report the findings of a switch from brand-name to generic clozapine in a Canadian outpatient population.

METHOD

The medical records of 58 outpatients diagnosed with schizophrenia and other psychotic disorders and stabilized on brand-name clozapine therapy were reviewed retrospectively. Patients were switched from brand-name to generic clozapine on their next dispensing supply after September 29, 2003. Data regarding clozapine dose regimens, physicians' visits, hospitalizations, and adverse events were collected from the patients' charts for the 6 months preceding and the 6 months after the switch from brand-name to generic clozapine. Relevant measurement changes in those data associated with the switch are evaluated.

RESULTS

No significant changes in dose, number of physician's visits, or hospitalization rates were observed as a consequence of the switch from brand-name to generic clozapine. In addition, there were no reported increases in the frequency of the most common adverse events, including decreases in white blood cell counts. None of the patients received a "nonrechallengeable" status, and no discontinuation of clozapine therapy occurred for any reason (toxicity or treatment failure) in the 6 months after the formulation switch.

CONCLUSION

In the current outpatient population, retrospective evaluation of the conversion from brand-name clozapine to the first generic alternative available on the Canadian market did not reveal any significant treatment changes.

Lithium and clozapine rechallenge: a retrospective case analysis

BACKGROUND

Clozapine is a uniquely effective antipsychotic, although its use is limited by the risk of neutropenia. Lithium is occasionally prescribed during a clozapine rechallenge, with the hope that it will prevent a second neutropenia or agranulocytosis. There are concerns, however, that lithium use will mask the onset of a neutropenia, leading to a more severe dyscrasia. The objective of this analysis was to determine the utility and safety of lithium coprescription in clozapine rechallenge.

METHOD

A retrospective case analysis was performed of all patients who had experienced a previous clozapine-induced blood dyscrasia and had a clozapine rechallenge with lithium coprescribed in a tertiary referral center between September 1998 and September 2003.

RESULTS

Twenty-five patients met the study criteria; 1 patient (4%) had a second episode of neutropenia or agranulocytosis while undergoing the rechallenge. This rate was significantly lower (p = .021) than the national (U.K.) rate (21.2%). Although recurrent dyscrasias were not more common, or more severe, than those seen with rechallenge in general, our single case did show some evidence that the patient's neutropenia was masked by lithium use.

CONCLUSION

This study provides support for the utility of lithium in preventing neutropenias in rechallenge; extra vigilance may be required, however, to detect masked blood dyscrasias.

[Invasive aspergillosis (IA) in patients treated in the Institute of Tuberculosis and Chest Diseases in the years 1993-2005--diagnostic problems]

The aim of this study was to present the diagnostic problems in pts treated for invasive aspergillosis (IA) in the IIIrd Clinic of the Institute of Tuberculosis in the years 1993-2005. The material consisted of clinical documentation of 18 pts. 15 out of 18 pts (83,4%) died. In all those cases autopsy examination was done. In 13 pts IA was the main and in another 2 only the accessory cause of death. All pts were treated with corticosteroids and/or cytostatic drugs because of lung cancer (13 pts), haematologic disorders (1 pts), Wegener's granulomatosis (3 pts) and idiopathic pulmonary fibrosis (1 pts). In 13 out of 18 pts granulocytopenia was revealed (on an average from 0,008 x 10(9)/L to 0,95 x 10(9)/L) one month before death. In 13 pts IA was limited to the lungs, in 5 others there were also fungal lesions in brain, kidneys, liver, spleen, pleura, pericardium and heart. Pts with disseminated form of IA had significantly lower granulocyte count and were treated with higher doses of corticosteroids than others. Immunosupressive drugs and granulocytopenia can be regarded as predisposing factors. IA was diagnosed before death only in 5 out of 18 pts. This was mainly caused by the lack of the symptoms of infection (4 pts) and negative results of mycological (6 pts) and serological examination (8 pts). We should underline that mycological examination was only done in 11 pts and serological examination of blood for fungal antigen only in 6 pts. We conclude that mycological infection ought to be searched in all pts treated with high doses of corticosteroids and those with prolonged granulocytopenia, especially if they have the symptoms of infection which does not respond to antibiotic therapy.

Relative incidence of agranulocytosis and aplastic anemia

Agranulocytosis and aplastic anemia are both rare, life-threatening blood dyscrasias. Agranulocytosis is mainly caused by medicines, whereas the etiology of aplastic anemia is largely unexplained. In two epidemiologic studies using the same methods, we observed a striking inverse relationship between the incidence of the two diseases in different regions, including five countries in Europe, and Israel and Thailand. The annual incidence of agranulocytosis ranged from 1.1 to 4.9 cases per million, and that of aplastic anemia, from 0.7 to 4.1 per million; the inverse correlation was consistent among the regions (R2 = 0.74). There is no clear explanation for this previously unreported pattern, but it seems unlikely to be due to methodology.

Hematological adverse events in clozapine-treated children and adolescents

OBJECTIVE

To retrospectively examine rates of hematological adverse events (HAEs) in psychiatrically ill, hospitalized children treated with clozapine.

METHOD

Clozapine treatment was administered in an open-label fashion using a flexible titration schedule, and data from weekly complete blood counts was obtained. The rate of neutropenia and agranulocytosis (HAEs) development was determined for 172 eligible patients (mean age at clozapine initiation, 15.03 +/- 2.13 years) with a median observation period of 8 months.

RESULTS

Neutropenia (absolute neutrophil count <1,500/mm) developed in 23 (13%) patients and agranulocytosis (absolute neutrophil count <500/mm) in one (0.6%) patient. The cumulative probability of developing an initial HAE at 1 year of clozapine treatment was 16.1% (95% confidence interval 9.7%-22.5%). Eleven (48%) of 24 patients who developed an HAE were successfully rechallenged on clozapine. Eight (5%) of 172 patients from this sample eventually discontinued clozapine because of an HAE (one agranulocytosis, seven neutropenia).

CONCLUSIONS

The occurrence of HAEs is a significant risk associated with the administration of clozapine. However, in this sample, few children actually discontinued therapy because of an HAE and the incidence of agranulocytosis does not appear higher than what has been reported in the adult literature.

Neutropenia, agranulocytosis and dipyrone

CONTEXT

Neutropenia and agranulocytosis may be defined as granulocyte counts of less than 1,500/mm3 and 500/mm3, respectively. Agranulocytosis is a rare and serious disease often caused by drugs. Its mortality rate is around 10%. The most common manifestations are infections such as tonsillitis, pharyngitis, stomatitis or pneumonia. Although dipyrone is one of the drugs known to be associated with agranulocytosis, the strength of the association has been a matter of much debate. Moreover, alternative analgesic and antipyretic agents are not devoid of serious side effects.

CONCLUSIONS

It is therefore necessary to establish the incidence of agranulocytosis in Latin America and the role of dipyrone. The ongoing LATIN Study is a multicenter international case-control study that will provide answers for these questions.

Incidence of aplastic anemia and agranulocytosis in Latin America--the LATIN study

CONTEXT AND OBJECTIVE

Aplastic anemia and agranulocytosis are rare but life-threatening disorders, often caused by drugs and other environmental exposures. Reported incidence of these diseases seems to vary between different geographic regions, and few data on their incidence are available for Latin American countries. The aim of this work is to determine the incidence of agranulocytosis and aplastic anemia in Brazil.

DESIGN AND SETTING

Incidence study. Seven centers took part in the pilot phase, so as to represent all Brazilian regions.

METHODS

Each center conducted an active search for new cases in a defined region by means of regular contacts with all hematologists, main clinical laboratories and clinicians in hospitals of the region.

RESULTS

74 patients with aplastic anemia and 16 with agranulocytosis were identified. Patients with agranulocytosis had a median age of 31 years (interquartile range, IQR: 12.5-48.2); 32.2% were male and 81.2% were white. The median age of aplastic anemia patients was 21 years (IQR 15.0-35.2); 62.2% were male, 50.0% were white and 39.2% mulatto. The incidence of agranulocytosis was estimated to be 0.5 cases per million individuals per year, ranging from 0.0 to 1.1 cases per million per year between regions. The incidence of aplastic anemia was 2.7 cases per million per year, ranging from 1.1 to 7.1 cases per million per year between regions.

CONCLUSIONS

Aplastic anemia and agranulocytosis are rare diseases in Brazil. However, there is considerable variability in their incidences between different regions.

Population-Based Drug-Induced Agranulocytosis

BACKGROUND

Since the publication of a major international case-control study on the risk of agranulocytosis associated with the use of medicines in the 1980s, many new drugs have been introduced in therapeutics.

METHODS

Seventeen units of hematology contribute to the case-control surveillance of agranulocytosis and aplastic anemia in Barcelona, Spain. After a follow-up of 78.73 million person-years, 177 community cases of agranulocytosis were compared with 586 sex-, age, and hospital-matched control subjects with regard to previous use of medicines.

RESULTS

The annual incidence of community-acquired agranulocytosis was 3.46:1 million, and it increased with age. The fatality rate was 7.0%, and the mortality rate was 0.24:1 million. The drug most strongly associated with a risk of agranulocytosis was ticlopidine hydrochloride with an odds ratio (OR) of 103.23 (95% confidence interval [CI], 12.73-837.44), followed by calcium dobesilate (OR, 77.84 [95% CI, 4.50-1346.20]), antithyroid drugs (OR, 52.75 [95% CI, 5.82-478.03]), dipyrone (metamizole sodium and metamizole magnesium) (OR, 25.76 [95% CI, 8.39-179.12]), and spironolactone (OR, 19.97 [95% CI, 2.27-175.89]). Other drugs associated with a significant risk were pyrithyldione, cinepazide, aprindine hydrochloride, carbamazepine, sulfonamides, phenytoin and phenytoin sodium, beta-lactam antibiotics, erythromycin stearate and erythromycin ethylsuccinate, and diclofenac sodium. Individual attributable incidences for all these drugs, which collectively accounted for 68.6% of cases, were less than 1:1 million per year.

CONCLUSIONS

Agranulocytosis is rare but serious. A few drugs account for two thirds of the cases. Our results also provide reassurance regarding the risk associated with a number of newly marketed drugs.

A prospective study of the incidence of agranulocytosis and aplastic anemia associated with the oral use of metamizole sodium in Poland

BACKGROUND

Metamizole is a common analgesic and antipyretic drug. However, its use has been associated with a risk of side-effects involving agranulocytosis and aplastic anemia. These reactions are rare and unpredictable. The aim of this prospective study was to evaluate the risks of these complications in Poland, where this medication is available without prescription.

MATERIAL/METHODS

Six hematological centers, serving approximately 40% (ca. 15 million people) of the country's population, participated in the study. All cases of agranulocytosis and aplastic anemia were recorded and their severity and association with the use of drugs, especially metamizole sodium, were evaluated. All the patients receiving cytostatic or immunosuppressive drugs were excluded.

RESULTS

During the 12 months of the study, 2 cases of aplastic anemia and no cases of agranulocytosis were confirmed which may have been associated with the use of metamizole. Overall, we recorded 16 cases of agranulocytosis and 27 cases of aplastic anemia. The two cases of metamizole sodium-induced aplastic anemia were non-fatal in character.

CONCLUSIONS

Considering the consumption of 112,300,094 tablets of metamizole in Poland a year, the figures obtained result in an incidence of 0.25 cases of aplastic anemia per 1 million persons per day of treatment; this value being less than that for other nonsteroidal anti-inflammatory drugs. Nevertheless, caution is recommended in the application of metamizole, particularly over long periods and in large doses.

Incidence of Agranulocytosis in Southwest France

BACKGROUND

Updated knowledge of background event rates is fundamental to risk assessment.

OBJECTIVE

To estimate the incidence of agranulocytosis in the general population in Southwest France.

METHODS

All definite cases of acute non-cancer drug-related agranulocytosis in subjects aged more than 16 years were systematically retrieved weekly from Medical departments or labs in the catchment area (approximately 3.5 millions inhabitants). Event rates were compared to population figures from 1999 census data, and Poisson 95% confidence intervals computed.

RESULTS

From January 1st 1997 to December 31st 1998, 87 cases of agranulocytosis were identified, 58 being validated by an independent ad hoc panel of experts. The overall annual incidence rate was 9.2 per million inhabitants (95%CI: 6.9;13.0); 7.7 (95%CI: 4.8;11.7) per million in men, and 10.5 (95%CI: 7.2; 14.8) per million in women. These rates of all-cause acute agranulocytosis can be used as expected background reference rate for specific risk assessment.

Neutropenia and agranulocytosis in England and Wales: incidence and risk factors

The objectives of this study were to estimate the incidence of idiosyncratic neutropenia and agranulocytosis in England and Wales and to evaluate their risk factors and outcomes. The study was conducted using data from the General Practice Research Database. All cases of idiosyncratic neutropenia or agranulocytosis were identified and the incidence was estimated. This was followed by a nested case-control study, estimating odds ratios with drug exposure from conditional logistic regression. From 1987 to 1999, 3,224 patients with idiosyncratic neutropenia (50 with agranulocytosis) were identified. The incidences of neutropenia and agranulocytosis were estimated to be 120 and 7 cases per million people per year, respectively. The adjusted odds ratios for neutropenia were 34.7 (95% confidence interval 12.0-99.7) for current users of thyroid inhibitors, 9.5 (4.4-20.8) for users of disease-modifying antirheumatic drugs, and 7.6 (4.9-11.9) for users of aminosalicylates. Other drugs with statistically significantly increased risks of neutropenia included antibacterial drugs, non-opioid analgesics, NSAIDs, antidepressants, ulcer-healing drugs, and anti-epileptics. The increase in risk of neutropenia predominantly occurred during the first months of treatment. For most drugs investigated in this study, there was no relationship to daily dose. The excess 1-year mortality was low among neutropenia and agranulocytosis cases and mostly explained by the underlying disease state. In conclusion, the highest risks of neutropenia were generally found in patients starting treatment. The excess 1-year mortality was low among neutropenia and agranulocytosis cases and can be mostly explained by the underlying disease state.

Risk of drug-induced agranulocytosis: the case of calcium dobesilate

BACKGROUND

In the last 20 years, some cases of agranulocytosis associated with calcium dobesilate consumption in Spain have been reported. A high risk of dobesilate-associated agranulocytosis (121 cases per million per year) calculated using both a case-control and a case-population strategy has been published. However few spontaneous reports have been noted in the same period of time. No explanation exists for this disagreement.

METHODS

Estimated incidence rates of agranulocytosis in the IAAAS study and the calculated risk of dobesilate-associated agranulocytosis were used as background risks in a Poisson-based methodology, to calculate the number of coincidental reports of agranulocytosis among patients treated with dobesilate. The influence of treatment duration, notification rate and population characteristics were calculated.

RESULTS

During the period 1978-2000, a total of 23 cases would have taken place if the background risk of agranulocytosis were 4.7 per million per year (IAAAS's risk); however, only 9 spontaneous cases of agranulocytosis associated to dobesilate were noted. A simulation showed that with notification rates equal to or higher than 17%, it was not possible to exclude that the 9 cases were false-positives. With notification rates equal or inferior to 16%, it would be unlikely that cases of agranulocytosis were noted in this population with a risk of 4.7 per million per year; therefore, it is necessary to assume a higher agranulocytosis risk. More than 1 case per year could be a false-positive if the background risk of agranulocytosis is 9.5 per million per year, this being the appropriate risk for a population of patients older than 60 years. The duration of treatment beyond 30 days increases the probability of a random coincidence of the intake of drug and an agranulocytosis event.

CONCLUSIONS

The disagreement between calculated dobesilate-associated agranulocytosis risk and the number of noted spontaneous reports may be explained by at least three different factors: under-reporting, duration of treatment and age of patients. It is possible, with the methodology presented, to estimate the influence of these factors to avoid confusion with possible false-positive cases and then to design the correct prospective trial that can provide the true agranulocytosis risk.

The incidence of metamizole sodium-induced agranulocytosis in Poland

Metamizole sodium continues to be used extensively as an analgesic in Poland. This study was the first undertaken to quantify the incidence of agranulocytosis associated with metamizole sodium in Poland, and to compare the findings with those from other countries. Based on data obtained retrospectively from medical records covering the period 1997-2001 in six haematology centres representative of Poland as a whole, the crude estimate obtained was a rate of 0.2 cases per million person-days of use. This is the same order of magnitude as the value from an epidemiological study covering several countries (0.3-4.0).

Agranulocytosis and other blood dyscrasias associated with dipyrone (metamizole)

OBJECTIVE

Agranulocytosis is a potentially lethal adverse drug reaction of dipyrone (metamizole). According to case-control studies, the frequency is low, approximately one per million users. The aim of the study was to describe the pattern of blood dyscrasias associated with dipyrone, identify possible risk factors and calculate the incidence of agranulocytosis associated with dipyrone.

METHODS

All spontaneous reports of serious blood dyscrasias associated with dipyrone in Sweden were reviewed. The reports were scrutinised for additional information, including bone marrow findings. The reported incidence of agranulocytosis was estimated from total prescription sales of dipyrone.

RESULTS

The reported incidence of agranulocytosis with dipyrone in Sweden was estimated to be at least 1:1439 (95% confidence interval 1:850, 1:4684) prescriptions. Ninety-two percent of the cases of blood dyscrasias occurred during the first 2 months of treatment. Additional risk factors were identified in 36% of the patients. In a total of five cases of which four were fatal, all three haematopoieses were affected according to bone marrow sample findings. Among the fatal cases, a higher proportion had bi- or tricytopenia than among the non-fatal cases ( P<0.005).

CONCLUSION

Based on sales data and spontaneous reporting of adverse drug reactions in Sweden, the risk of agranulocytosis with dipyrone seems to be considerably higher than the previously estimated risks. Dipyrone is also associated with other blood dyscrasias, and the prognosis for combined dyscrasias seems to be poorer than for isolated agranulocytosis.

[Risk of drug-induced agranulocytosis: an approximation to risk analysis arising from spontaneous notification of agranulocytosis cases among patients treated with calcium dobesilate]

BACKGROUND

Frequently, decisions about the safety of drugs are based on isolated cases of patients that develop a disease, while they have been taken a drug. A new method to detect, using spontaneous reporting, increases in agranulocytosis risk among patients treated with calcium dobesilate is shown.

METHOD

Using data of dobesilate sales, the maximum number of patients treated in a year was calculated. Spontaneous reports of agranulocytosis associated to dobesilate notified along the period 1985-2000 were identified. The number and the maximum number of cases explained by the agranulocytosis risk in a general population were calculated using the distribution of Poisson, assuming several reporting rates. Similarly, the influence of number of patients older than 60 and the duration of exposure to the drug were analysed.

RESULTS

The number of spontaneously reporting cases of agranulocytosis associated to dobesilate, in the period 1985-2000 was not greater than the maximum number of cases predicted by the agranulocytosis risk in a general population. Probably, a high number of dobesilate-treated patients had an advanced age and/or took the drug during several months. In these conditions, it is more difficult to identify an increase of risk associated to drug.

CONCLUSIONS

To calculate the risk of agranulocytosis associated to a drug is required to consider the basal risk of agranulocytosis in a general population as well as its possible modifications in the population of patients treated with the drug.

Utilization pattern of metamizole in northern Sweden and risk estimates of agranulocytosis

OBJECTIVE

This study was carried out in order to investigate the utilization pattern of metamizole to better estimate the quantitative risk of agranulocytosis since a cluster of such cases have been observed in Sweden.

METHODS

Cases of agranulocytosis submitted to the Swedish Adverse Drug Reactions Advisory Committee (SADRAC) between 1996 and 1999 were identified. Based on the utilization pattern of metamizole in inpatients at three hospitals and in outpatients in two counties in northern Sweden risk estimates of agranulocytosis during metamizole treatment were estimated. The utilization of metamizole was investigated by scanning 3567 case records at 10 hospital departments as well as stored prescriptions at six pharmacies during a 3-month study period.

RESULTS

Ten cases of agranulocytosis during treatment with metamizole have been reported to SADRAC over the period 1996 to 1999. During the 3-month study period metamizole was prescribed to 666 (19%) inpatients. Of these, approximately 96% received the drug for less than 1 week, 7.2% had used the drug previously. At the participating pharmacies 112 metamizole prescriptions for outpatients were found. The drug was prescribed in 34% for less than 1 week, in 28% for 7-15 days, and in 38% for more than 15 days. The mean prescribed daily dose was 2.7 g. Given certain assumptions including the actual amounts prescribed the calculated risks of agranulocytosis would be approximately one out of every 31,000 metamizole-treated inpatients and one of every 1400 metamizole-treated outpatients.

CONCLUSION

This study indicates that in most inpatients the use of metamizole in northern Sweden was within the approved indications for the drug. However, a considerable number of outpatients received the drug for a longer time than recommended and this may carry an increased risk for developing agranulocytosis.

Nonchemotherapy drug-induced agranulocytosis: experience of the Strasbourg teaching hospital (1985-2000) and review of the literature

Agranulocytosis is a life-threatening disorder that frequently occurs as an adverse reaction to drugs. The overall incidence of nonchemotherapy drug-induced agranulocytosis (DIA) ranges from 2.6 to 10 cases per million patients exposed to drugs per year. Although patients experiencing DIA may initially be asymptomatic, the severity of the neutropenia usually leads to severe sepsis, requiring intravenous broad-spectrum antibiotic therapy. In this setting, old age, septicaemia, shock, and the metabolic complications of infection, such as renal failure, are poor prognostic variables. The severity of neutropenia (< 0.1 x 10(9))/l) and its duration (> 10 days) may also impact negatively on the outcome. With appropriate management using pre-established procedures, the mortality rate is now around 5%. Haematopoietic growth factors have been shown to shorten the duration of neutropenia in DIA. However, it has yet to be determined whether their use translates into a better outcome in DIA patients experiencing sepsis. DIA still remains a rare event. 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.

A follow-up study of a population of schizophrenic patients treated with clozapine

1. Clozapine is a dibenzodiazepine neuroleptic which presents the advantage of not having undesirable neurological side-effects. Its efficacy for the treatment of the symptoms of schizophrenia is known, but the use of clozapine is limited to treatment-resistant schizophrenic patients as it induces agranulocytosis with a higher incidence than that of other neuroleptic drugs. 2. The present study was designed in order to evaluate the benefit/risk of chronic treatment. The analysis was performed using the files of schizophrenic patients. These patients were not stabilized by a classical neuroleptic treatment and/or presented individual secondary effects. 3. Clozapine induced neutropenia and 1 case of agranulocytosis in 3 females. Analysis of leukocyte expression highlighted some premonitory symptoms in patients who presented neutropenia. The observation of 2 to 3 early successive peaks in leukocyte expression (between the third and tenth week of treatment) could be predictive of neutropenia in the 3 to 4 months of treatment. 4. The patients who presented a lower leukocyte base-line following a peak had a higher risk, of developing neutropenia. This might explain some late accidents beyond the first six months of treatment. 5. The present study confirmed the advantages of clozapine treatment and demonstrated that the risk of neutropenia may be diminished by the detection of premonitory symptoms and the early monitoring of patients at risk i.e. female patients and subjects with a lower leukocyte base-line.

Agranulocytosis associated with calcium dobesilate clinical course and risk estimation with the case-control and the case-population approaches

OBJECTIVE

Calcium dobesilate is used in the treatment of diabetic retinopathy, chronic venous insufficiency, haemorrhoids and other ill-defined vascular conditions. It has been associated with agranulocytosis in anecdotal reports. We describe the clinical course of a series of patients who developed agranulocytosis while taking this drug, and we estimate the risk by means of both a case-control and a case-population strategy.

METHODS

All cases of agranulocytosis meeting strict predefined diagnostic criteria in an area of 3.3 to 3.9 x 106 inhabitants in the period 1980-1998 were identified. Cases and age-, gender- and hospital-matched controls were interviewed with a structured questionnaire including a detailed drug history. Each case was reviewed and confirmed by a haematologist, who was blind with respect to drug exposures. Consumption data were used to estimate the risk of agranulocytosis associated with calcium dobesilate using a case-population approach in which the incidence of agranulocytosis among users of calcium dobesilate was compared with that among the non-exposed population.

RESULTS

After a follow up of 68.55 x 10(6) person-years, 345 cases of agranulocytosis (242 community cases) were assembled. Reliable information was obtained from 216 cases. Two patients exhibited positive rechallenge. Twelve cases (5.6%) and 5 of 1380 controls (0.4%) had taken calcium dobesilate in the week before. With the case-control approach, the odds ratio was 23.66 [95% confidence interval (CI), 7.54-74.24], the attributable risk was 5.3% (95% CI, 3.0-9.4), and the number of cases attributable to dobesilate in the study area during the study period was 12.8. The case-population estimates were an incidence of 121.03 cases per 10(6) patient-years, a relative risk of 39.55 (95% CI, 17.96-77.49), an attributable risk of 6.73% (CI 3.4-12.9), and 16.30 cases attributable to dobesilate in the study area during the study period.

DISCUSSION

This study adds to evidence indicating that the case-population method is adequate for the study of rare type B adverse drug reactions. An additional advantage of this approach is that the incidence of the disease of interest among those exposed to the drug can be estimated. The risk of agranulocytosis associated with calcium dobesilate should be considered in relation to poor evidence of its clinical efficacy.

Haematological safety of antipsychotic drugs

Many clinicians have become concerned about the safety of new antipsychotics particularly in view of the association of agranulocytosis with clozapine and of aplastic anaemia with remoxipride. The Committee on Safety of Medicines and Medicines Control Agency 'yellow card' post-marketing surveillance data were analysed for reports of haemopoietic disorders with the 16 antipsychotics in common use. Corrections for relative risk were made in three separate ways: (i) control for degree of use, using Northern Ireland prescribing data for 1995; (ii) percentage of total reports from 1963 to 1996; and (iii) examination of the first 5 years' post-marketing data only. After clozapine and remoxipride the highest risks of haemopoietic reactions appeared to be associated with the aliphatic phenothiazine derivatives thioridazine and chlorpromazine. There is therefore no evidence of any increased risk with high-potency drugs such as haloperidol or pimozide or with the newer drugs such as sulpiride or risperidone. Continued vigilance, however, is necessary as more new atypicals become available and begin to be widely prescribed.

Blood dyscrasias in clozapine-treated patients in Italy

BACKGROUND AND OBJECTIVE

Clozapine is a dibenzodiazepine derivative that is more effective than standard neuroleptic drugs in refractory schizophrenic patients, but its introduction in some countries was delayed by its propensity to cause blood dyscrasias. However, over the last ten years, different reports have clearly demonstrated that agranulocytosis and neutropenia can be easily prevented by means of strict hematologic surveillance. This article reviews the results of the first five years of the Italian Clozapine Monitoring System (ICLOS).

DESIGN AND METHODS

The hematologic parameters of 2,404 patients registered between 1995 and 1999 were collected in a central database, before the patients began clozapine-treatment, weekly for the first 18 weeks, and then monthly throughout the duration of therapy. On the basis of conventional criteria, different risk levels have been identified with total leukocyte <3. 0x10(9)/L and/or an absolute neutrophil count <1.5x10(9)/L leading to immediate discontinuation of the drug.

RESULTS

The analysis shows that 0.9% of the patients developed neutropenia and 0.7% agranulocytosis, mainly during the first 18 weeks of clozapine treatment. Drug discontinuation led to the normalization of hematologic parameters in all cases, and the use of growth factors reduced the risk of infectious complications. Transient leukocytosis and eosinophilia were also observed but these did not have any serious clinical effects.

INTERPRETATION AND CONCLUSIONS

The ICLOS study confirms that regular hematologic monitoring is highly effective in minimizing the incidence of clozapine-associated blood dyscrasias. The lower than initially expected rates of agranulocytosis and associated deaths are encouraging in view of the benefits of this drug in treatment-resistant schizophrenia and other neurologic disorders.

Estimating risks for matching factors in case-control studies

Matching for factors such as age and sex is a convenient method for minimizing confounding in case-control studies, but it does not allow inferences about the effects of the matching factors unless case ascertainment is virtually complete and the distribution of the matching factors in the source population is known. When this is so, the effect of a particular factor can be estimated by comparing the population distribution of that factor with what is observed in the case series. Such a comparison, however, may itself be confounded by other factors that are related to both the matching factors and the disease under investigation. This article proposes a method for evaluating matching factors as risk factors, which uses information on the distribution of potential confounders in the reference series and exposure relative risk estimates to adjust the person-time proportionality constant in a Poisson regression model. The method is particularly suited to data sets in which many of the elementary matching strata contain few or no cases and/or controls. It makes use of standard analytic procedures, but requires the estimation of an additional variance-covariance component for the estimated Poisson regression coefficients. Further factors that may confound the relationship between exposure and disease are easily accommodated. The method is demonstrated in two examples: a matched case-control study of drugs in relation to the rare blood dyscrasia, agranulocytosis, that was conducted in Europe and Israel, and a case-control study of ovarian cancer in Australia.

Agranulocytosis induced by pyrithyldione, a sedative hypnotic drug

OBJECTIVE

Pyrithyldione, a sedative-hypnotic drug with a poor clinical pharmacological development, was associated with anecdotal cases of agranulocytosis in the 1940s in the USA, in the 1960s and 1970s in the ex-Democratic Republic of Germany and in the 1980s in Japan. We describe the estimation of the risk of agranulocytosis associated with its use in Spain, which led to its withdrawal from the market.

METHODS

In collaboration with the haematology units of all the hospitals in a defined area (3.3-3.9 x 10(6) inhabitants), all cases of agranulocytosis meeting strict diagnostic criteria were identified. Each case - defined as an episode of agranulocytosis - was reviewed by a haematologist without knowledge of previous drug exposures. Cases and age-, gender- and hospital-matched controls were interviewed with a structured questionnaire about previous drug exposures. In addition, in order to estimate the risk of pyrithyldione-associated agranulocytosis through a case-population approach, its consumption among the cases was compared with its consumption among the general population.

RESULTS

After a follow-up of 66.5 x 10(6) person-years, 330 cases of agranulocytosis (230 community cases) were assembled. Reliable information on previous exposures was obtained for 204 cases. They were compared with 1314 controls. Eleven patients (14 cases, 6.9%) and zero controls had been exposed to pyrithyldione. The adjusted OR was 200.11 (CI 95% 22. 62-infinity). All patients were female; none had a fatal outcome; three exhibited positive rechallenge; and all had concomitantly taken other drugs. Although pyrithyldione was a prescription-only medicine, only 8% had been dispensed with medical prescriptions. Assuming the worst case, i.e. that all the exposed cases could be attributed to pyrithyldione, the incidence was 35.6 cases per 100, 000 patient-years (95% CI, 18.9-60.9), which gives a risk ratio estimate of 109.6 (57.5-191.5) if compared with the incidence of agranulocytosis among the non-exposed population [3.26 cases (CI 95% 2.83-3.71) per 10(6) inhabitants and per year].

DISCUSSION

Pyrithyldione was viewed by pharmacists as a mild hypnotic, and apparently this had conferred to this drug an unjustified image of safety. The National Commission of Pharmacovigilance recommended to the Ministry of Health its withdrawal from the market when eight cases of agranulocytosis had been identified. However, it took more than 2 years to withdraw it, and six additional cases occurred in the study area. This illustrates the need for quick regulatory action when pharmacoepidemiological data suggest an unfavourable benefit/risk ratio.

Agranulocytosis in Bangkok, Thailand: a predominantly drug-induced disease with an unusually low incidence. Aplastic Anemia Study Group

Agranulocytosis, a syndrome characterized by a marked reduction in circulating granulocytes, is strongly associated with medical drug use in Europe and the United States. Unregulated use of common pharmaceutical agents in developing countries has been suspected of causing large numbers of cases of agranulocytosis and deaths, especially among children. To elucidate the incidence and etiology of agranulocytosis in Thailand, a population-based case-control study of symptomatic agranulocytosis that resulted in hospital admission was conducted in Bangkok from 1990 to 1994. An attempt was also made to study the disease in Khonkaen (in northeastern Thailand) and Songkla (in southern Thailand), but there were insufficient cases in the latter regions, and the analysis was confined to subjects from Bangkok. In that region, the overall incidence of agranulocytosis was 0.8 per million per year; there were no deaths. As expected, the incidence was higher in females (0.9 per million), and it increased with age (4.3 per million beyond age 60). Among 25 cases and 529 controls the relative risk estimate for a combined category of all suspect drugs was 9.2 (95% confidence interval = 3.9-21), and the proportion of cases that could be attributed to drug use was 68%. For individual drugs and drug classes the data were sparse; within these limitations, the strongest association appeared to be with antithyroid drugs. One case and three controls were exposed to dipyrone, a drug known to cause agranulocytosis; with such scanty data the risk could not be evaluated. Exposure to pesticides or solvents was not associated with an increased risk. This is the first formal epidemiologic study of agranulocytosis in a developing country. As in the West, most cases are attributable to medical drug use. However, the incidence of agranulocytosis in Bangkok, and apparently, in Thailand as a whole, is unusually low, and the disease does not pose a public health risk.