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.

Hospitalizations for aplastic anemia and agranulocytosis in Saskatchewan: incidence and associations with antecedent prescription drug use

A population-based study to estimate the incidence of hospitalizations for aplastic anemia and agranulocytosis and to evaluate associations between these disorders and antecedent prescription drug use was performed using the Saskatchewan administrative health care databases. Hospital charts and cancer registration data were utilized to apply strict diagnostic criteria to case identification. Estimates of the annual incidence of aplastic anemia and agranulocytosis were 2.7 and 3.0 per million, which are similar to those from other recent population-based studies with comparable case identification criteria. Only a small number of cases were available to evaluate potential drug causes, leading to an analysis of limited power. Nevertheless, significant associations were found between aplastic anemia and tocainide, gold salts, and antidepressants; and between agranulocytosis and anti-thyroids, trimethoprim-sulfamethoxazole, beta-lactams, sulfasalazine, chlorpromazine, carbamazepine, glyburide, and procainamide, although the associations with antibiotics may indicate a response to the disorders rather than a possible cause. These findings are generally consistent with the results of other case-control investigations.

Clozapine treatment in Australia: a review of haematological monitoring

BACKGROUND

Clozapine is an atypical antipsychotic drug indicated for patients with schizophrenia in whom traditional antipsychotic drugs (such as haloperidol or the phenothiazines) are ineffective, or in those who experience intolerable adverse effects. Clozapine treatment may be complicated by the development of life-threatening agranulocytosis, so regular haematological monitoring is required.

OBJECTIVES

To determine the incidence of clozapine-induced agranulocytosis in Australia and the importance of monitoring white blood cell counts in patients treated with clozapine.

DESIGN

Review of haematological monitoring for the first three years (June 1993-July 1996) of operation of the Australian Clozaril (clozapine; Novartis Australia) Patient Monitoring System (CPMS) central database.

RESULTS

In the 4061 patients prospectively monitored by the CPMS, the incidence of agranulocytosis, neutropenia and leukopenia combined was 2.6% (n = 104); the incidence of agranulocytosis was 0.9% (n = 37). So far there have been no deaths in Australia from the complications of clozapine-induced agranulocytosis.

CONCLUSION

The incidence of agranulocytosis and neutropenia associated with clozapine use in Australia is similar to that in the rest of the world. Monitoring the white blood cell counts of patients being treated with clozapine ensures minimal risk to patients who develop agranulocytosis.

Suicide in schizophrenia: risk factors and clozapine treatment

Suicide is the major cause of premature death in patients with schizophrenia. Among these patients, 40% report suicidal thoughts, 20% to 40% make unsuccessful suicide attempts, and 9% to 13% end their lives by suicide. Traditional antipsychotic drugs undertreat many schizophrenic patients and can produce serious side effects, such as tardive dyskinesia. Clozapine is the only antipsychotic drug that has been shown in controlled clinical trials to be effective in reducing both positive and negative symptoms in schizophrenic patients who fail to respond to typical neuroleptic drugs. The potential decrease in suicide among schizophrenic patients treated with clozapine is estimated to be as high as 85%. Treatment with clozapine is cost-effective, and the significant decrease in the risk of suicide far outweighs the very low risk of mortality from agranulocytosis. Clozapine should be considered for treatment of both neuroleptic-resistant and neuroleptic-responsive schizophrenic patients who have persistent suicidal thoughts or behavior.

Maximizing clozapine therapy: managing side effects

Since its introduction to the United States in 1990, the benefits of clozapine use have been repeatedly validated. Clozapine remains the only antipsychotic with proven efficacy in treatment-resistant schizophrenia. Because clozapine has been part of the psychiatric pharmacopeia for considerably less time than neuroleptics, which have dominated the field for over 4 decades, its underutilization may be partly attributed to a lack of experience in managing associated side effects. Most side effects associated with clozapine are typical of antipsychotics in general, and with clozapine, these side effects are typically benign, tolerable, and manageable. It is conceivable that there remains a concern over the risk of agranulocytosis. However, the mandatory blood monitoring carried out through the Clozaril National Registry has considerably reduced the incidence of fully developed cases of agranulocytosis from premarketing values of approximately 1% to 2% to current values of 0.38% and virtually prevented mortalities. These values are likely to decrease further with the application of cytokine augmentation therapy among patients developing blood dyscrasias. Many side effects of clozapine are observed early after treatment onset and are greatly reduced by dose adjustments. Appropriate management of side effects will facilitate a maximization of the benefits of clozapine treatment. Clearly, the benefits of clozapine therapy far outweigh its risks.

Reducing clozapine-related morbidity and mortality: 5 years of experience with the Clozaril National Registry

The Clozaril National Registry (CNR) was created to help protect patients from developing potentially fatal agranulocytosis secondary to treatment with the antipsychotic medicine clozapine. The CNR, designed and maintained by the manufacturer of the branded Clozaril (clozapine), has the principal goals of (1) prophylaxis-preventing inappropriate retreatment, and (2) quality assurance-overseeing adherence to a "no blood, no drug" policy. This article reviews the estimated impact of the CNR on clozapine-related morbidity and mortality over the first 5 years of commercial experience in the United States.

METHOD

Complete data on leukopenia and agranulocytosis, gathered from the CNR database for the period of 1990-1994, were reviewed and compared with data from the pre-CNR period.

RESULTS

Use of clozapine in 99,502 patients according to package labeling requirements (distribution of the medicine linked to mandated white blood cell count testing) was associated with a total of 382 cases of agranulocytosis (0.38%) versus an expected cumulative total of 995 cases (based on the pre-CNR rate of 1% to 2%). Based on the expected agranulocytosis rate, up to 149 deaths might have been anticipated. Instead, there were only 12 deaths attributed to complications of agranulocytosis.

CONCLUSION

The CNR provides for universal rechallenge protection as well as controlled dispensing of clozapine. It also serves as an early warning system to promote the safe and effective use of clozapine. The CNR includes quality assurance mechanisms designed to enhance compliance. Despite the added logistic requirements this system places upon physician, pharmacist, and manufacturer, the CNR has helped to reduce substantially potential fatal outcomes. The CNR reinforces both patient and treatment system compliance. Based on this favorable experience concerning agranulocytosis and associated fatalities, the Neuropsychopharmacology Advisory Committee to the U.S. Food and Drug Administration has unanimously recommended a reduction in frequency of the white blood cell count testing requirement after 6 months to every 14 days, instead of weekly. Finally, the CNR database containing white blood cell count and demographic data on every patient in the United States who has received the medicine has served as a unique epidemiologic database.

Drug-associated agranulocytosis: 20 years of reporting in The Netherlands (1974-1994)

In this descriptive study, all 425 reports were included concerning drug-associated agranulocytosis as registered between 1974 and 1994 in the files of the Drug Safety Unit of the Dutch Inspectorate for Health Care. All reports were analysed as to the probability of agranulocytosis or neutropenia according to previously defined criteria. Subsequently, the causal relationship between exposure and outcome was assessed. It concerned 149 men and 271 women. One hundred and twelve reports were unclassifiable because age, gender, or total number of leukocytes at the time of reaction were unknown. In 100 reports agranulocytosis was probable, in 78 possible, in 8 reports neutropenia was probable, in 20 reports neutropenia was possible, and in 107 reports agranulocytosis or neutropenia were unlikely. In the 13 reports of probable agranulocytosis or neutropenia with a certain causal relationship, causative drugs were cimetidine, dipyrone, sulphasalazine, methyldopa, spironolactone, propylthiouracil (2), thiamazole, sulphamethoxazole with trimethoprim, gentamicin, a combination preparation containing aminophenazone, benzylpenicillin and indomethacin. The individual drugs most often reported to cause agranulocytosis or neutropenia were: dipyrone (19), mianserin (15), sulphasalazine (13), sulphamethoxazole with trimethoprim (11), the group of penicillins (9), cimetidine (8), the thiouracil derivatives (8), phenylbutazone (8), and penicillamine (8). Agranulocytosis is a serious and fairly frequently reported adverse reaction. The reporting system of the Drug Safety Unit can be used very well for signal generation concerning adverse reactions to drugs.

[Retrospective study of drug-induced agranulocytosis in hospitalized patients in Geneva and comparison with cases reported to IOCM]

In a retrospective study, 19 cases classified as idiosyncratic drug-induced agranulocytosis were found among 162 files of patients hospitalized in internal medicine clinics of the university hospital where this diagnosis had been coded. This would give an estimated incidence of 2.6 cases per million inhabitants per year for the Geneva area. In most cases several drugs were implicated in causation of the episodes. Suspected drugs were those commonly reported in the literature, but also some drugs which might already have been taken to treat infectious complications of agranulocytosis. A comparison of the Geneva cases with those notified to the Swiss Intercantonal Office for the Control of Medicines reveals a similar profile of involved drugs.

Cost-effectiveness of clozapine monitoring after the first 6 months

BACKGROUND

Clozapine is effective in treating patients with schizophrenia who do not respond to conventional neuroleptic drugs. The drug is unique in that it is available only with a US Food and Drug Administration-mandated system for weekly monitoring of patients' white blood cell counts. No study has been conducted to evaluate the cost-effectiveness of this mandatory monitoring system.

METHODS

A benchmark case was established by utilizing cumulative incidence rates of agranulocytosis from a recent study with a large sample of clozapine-treated patients. We assumed a 20% mortality among patients with agranulocytosis, $30.61 in monitoring costs each week, and 14.4 years of remaining life expectancy after detection of agranulocytosis. Based on these bench-mark assumptions, cost-effectiveness ratios in dollars per quality-adjusted life-year were calculated for the first, second, and third 6-month periods during which a patient was receiving clozapine. Sensitivity analyses were performed with more conservative assumptions in 5 alternative scenarios.

RESULTS

In the benchmark case, costs per quality-adjusted life-year gained were $61,694, $925,418, and $420,644 for the first, second, and third 6-month periods of clozapine treatment, respectively. In the alternative scenarios, these costs ranged from $7923 to $46,056 for the first 6-month period and from $54,025 to $690,850 for the second and third 6-month periods.

CONCLUSIONS

While the costs of monitoring patients with schizophrenia in the first 6-month period of clozapine treatment seem to be justifiable, monitoring thereafter may not be cost-effective because of the very low incidence of agranulocytosis in the later periods.

[Acute drug-induced agranulocytosis: experience of the Regional Center of Pharmacovigilance of Lyon over 7 years]

Sixty-two cases of drug-induced agranulocytosis, spontaneously reported to the regional drug monitoring centre in Lyon from 1988 to 1994, have been analysed. The mean age of patients was 58.6 years, and sex ratio was 1:1. The mean delay of onset was 46.2 days and absolute neutrophil counts (ANC) dropped below 0.1 x 10(9)/l in 73 per cent of patients. Bone marrow aspirates disclosed absence of myeloid series in 28 per cent of investigated cases. Neutrophil recovery occurred after a mean of 9.3 days, and the overall fatality rate was 6.5 per cent. Haematopoietic growth factors (HGF) were used in 11 patients with an ANC below 0.1 x 10(9)/l and/or a hypoplastic bone marrow. We have found no clear indication for a potential benefit of HGF treatment, but HGF were usually administered late during the course of neutropenia, i.e., after a mean of 6 days. The incidence rate estimated for people living in the Rhône administrative division was 3.3 per million per year, similar to that found in epidemiological studies. Drugs most frequently involved were anti-infective agents and psychotropic drugs.

Confidence intervals for the excess risk in case-control studies

Kaufman et al. compute the 'excess risk' of a disease in the presence of an exposure as the product of the incidence rate of the disease in the source population, the complement of the aetiologic fraction and the relative risk minus one. Methods for calculating confidence intervals for this quantity are derived when (as in case-control studies) the relative risk is estimated by the odds ratio, firstly from multiple logistic regression analysis and secondly without adjustment for covariates. For the latter an innovative approach based on confidence bounds for the two exposure parameters is suggested. The performance of these systems of confidence intervals is assessed by simulation for the former and by exact enumeration of the distributions involved in the latter. Illustrative examples from a study of agranulocytosis and indomethacin are presented.

Vesnarinone-induced granulocytopenia: incidence in Japan and recommendations for safety

Vesnarinone (OPC-8212) is a new positive inotropic agent that augments myocardial contractility. A recent multi-center randomized trial in the United States demonstrated that 60 mg/day of vesnarinone significantly reduced morbidity and mortality and improved quality of life in patients with symptomatic chronic heart failure. Vesnarinone, however, is also known for its propensity to cause granulocytopenia. In search of effective safety measures against this side effect, data have been collected in Japan as part of the post-marketing surveillance of this drug. This article reviews the results of this post-marketing surveillance and other works available to date, including an illustrative case report, and presents measures that should be taken with regard to safety during treatment with vesnarinone. Vesnarinone-induced granulocytopenia has appeared in relatively early stages of vesnarinone therapy, and characteristically results in a rapid decrease in granulocyte count. Hematologic monitoring should be performed at least once a week during the initial 16 weeks of vesnarinone therapy. Granulocyte colony-stimulating factor may contribute to recovery from severe granulocytopenia, although it should be used carefully because of its potential to cause adult respiratory distress syndrome.

[Acute drug-induced agranulocytosis. Clinical study apropos of 30 patients and evolution of etiologies over 2 decades]

Between 1982 and 1993, 30 patients were treated for drug-induced agranulocytosis. They did not receive cytotoxic chemotherapy nor radiotherapy during the past 6 months. There is a higher incidence in women (21 females, nine males). Mean age is 59.3 years old. The drug could be found in 25 cases including noramidopyrine five cases, antithyroid drugs four cases, non steroidal anti-inflammatories drugs four cases. Five patients died of infection during agrulocytosis. Sepsis was documented in three cases. We used hematopoietic growth factors in two cases. Neutrophils rose up to 0.5.10(9)/l between 2 to 14 days after the diagnosis and 1.10(9)/l between 3 to 16 days. Time when absolute neutrophil count was less than 0.5.10(9)/l was shorter (p = 0.008) when bone marrow was rich with maturation arrest but with few or no mature forms rather than reduction of granulocytic precursors. By comparison with a similar study made in the same institution between 1971 and 1981, there were fewer cases each year. Drugs involved were not similar: phenicols were not found, reference to noramidopyrine is less frequent. Now antithyroid drugs is becoming one of the most important etiologies.

Risks of rhG-CSF treatment in drug-induced agranulocytosis

Nine patients with drug-induced agranulocytosis received recombinant human granulocyte colony-stimulating factor (rhG-CSF) to accelerate myeloid recovery because of life-threatening infections related to neutropenia. All patients showed a quick recovery of their granulocyte counts. Side effects were substantial, however. Three patients, two with a severe infection and one with preexisting pulmonary infiltrates, developed worsening of their respiratory status during neutrophil recovery, resulting in clinical manifestations of the adult respiratory distress syndrome (ARDS). In view of these major complications, the exact place of hematopoietic growth factors in the treatment of drug-induced agranulocytosis remains to be determined.

Clozapine-induced transient white blood count disorders

BACKGROUND

The aim of the study was to shed more light on the incidence and course of clozapine-induced transient white blood count (WBC) disorders.

METHOD

In an analysis of our clozapine drug monitoring program, we evaluated the data of 68 patients receiving clozapine for the first time. Incidence rates were calculated by actuarial life table analysis. The potential influence of sex, age, dose, and plasma level was evaluated using discriminant analysis.

RESULTS

Two patients developed progressive neutropenia, leading to agranulocytosis in one case. We also found the following transient hematologic dysfunctions: neutropenia (22.0%), eosinophilia (61.7%), and leukocytosis (40.9%). One patient showed chronic leukocytosis. Additionally, minor changes in the number of lymphocytes, monocytes, and basophilic granulocytes were detected in the study population.

CONCLUSION

Hematologic side effects are frequently induced by the atypical antipsychotic clozapine. Next to agranulocytosis, a progressive and potentially lethal hematologic adverse effect, most of the WBC disorders are transient and appear to be harmless.

Agranulocytosis: incidence and risk factors

The use of clozapine has been limited by the risk of agranulocytosis. The cumulative incidence of agranulocytosis is 0.80% after 1 year and 0.91% after 1 1/2 years. Risk is greatest during the first 3 months of treatment and greater among women and the elderly. White-cell counts tend to spike upward before the occurrence of agranulocytosis. The occurrence of a white-cell count spike of > or = 15% above the previous count predicts development of agranulocytosis within 75 days (risk ratio = 3.02; 95% confidence interval, 1.38-6.57). Our results indicate that hematologic monitoring is necessary and effective. They also suggest that the frequency of monitoring could be reduced after the initial period of maximal risk.

Emergencies caused by side effects of psychiatric medications

Psychiatric medications cause side effects in several organ systems that need emergency evaluation and treatment. Serious cardiovascular side effects include postural hypotension, cardiac conduction blockade, and SA mode dysfunction; serious neurological side effects include extrapyramidal reactions, seizures, delirium, catatonia, pseudotumor cerebri, ataxia, and glaucoma; serious genitourinary side effects include urinary retention, nephrotic syndrome, and priapism, and the serious hematological side effect of agranulocytosis. Also potentially fatal syndromes secondary to psychiatric drugs are the neuroleptic malignant syndrome, hyperandrenergic crisis, the serotonin syndrome, and lithium toxicity. Individual psychiatric drug classes most notorious for causing side effects with high morbidity and mortality are low potency neuroleptics, clozapine, tertiary tricyclics, monoamine oxidase inhibitors, and lithium.

Antithyroid drug-induced agranulocytosis: clinical experience with ten patients treated at one institution and review of the literature

The frequency, predisposing factors and course of agranulocytosis (granulocytes < 250/microliter) secondary to antithyroid drugs were studied in a cohort of 1256 continuously treated outpatients with hyperthyroidism during the 15 year period from 1973 to 1987. Two cases of agranulocytosis were detected; the frequency was 0.18% (95%-confidence intervals, 0.0-0.44%). This prevalence appears to be lower than reported in previous studies (up to 1.8%). For other adverse drug reactions, there was a clear-cut relationship to initial thionamide dose and to the body mass index; most reactions occurred during the first weeks of treatment. In addition, eight patients referred for thionamide drug- induced agranulocytosis were studied, and the following results obtained: Methimazole dose in patients with agranulocytosis was almost twice as in other patients (63.3 +/- 19.7 vs 34.3 +/- 29.7 mg daily) suggesting that this complication was related to dose. The interval between start of antithyroid drug treatment and first symptoms of agranulocytosis was 33 days (median; range, 23-55 days); hence, prolonged treatment beyond this period would appear relatively safe. Withdrawal of the causative agent and treatment of infection led to recovery of leukocyte counts within 15 days (median; range, 5-31 days). Two fatal outcomes were seen in referred patients. In one severely hyperthyroid patient with methimazole-induced agranulocytosis, recombinant human granulocyte/macrophage colony stimulating factor induced clinical and hematologic recovery within a few days of administration. In conclusion, agranulocytosis is the most severe side effect of antithyroid drugs. According to our results and a literature review, it occurs almost exclusively during the first ten weeks of treatment and is probably related to the drug dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Risk of agranulocytosis and aplastic anemia in relation to history of infectious mononucleosis: a report from the international agranulocytosis and aplastic anemia study

The general objective of this study was to evaluate the risks of agranulocytosis and aplastic anemia in relation to drug use. Other potential risk factors, including history of infectious mononucleosis, were also evaluated. In an international population-based case-control study, cases of agranulocytosis and aplastic anemia and controls, who were patients with selected diagnoses, were identified from the same hospitals. Information on drug use was obtained in a structured interview. Limited information on environmental exposures and on selected items of medical history, including infectious mononucleosis, was also recorded. The possible effects of these factors on the risk of the two blood dyscrasias were evaluated. Relative risks were estimated by stratified analysis and by multiple logistic regression. Among 319 cases of agranulocytosis, 12 patients (4%) gave a history of infectious mononucleosis at least 1 year previously; among 2180 controls the corresponding number was 11 (0.5%) (multivariate relative risk estimate, 6.2; 95% confidence interval, 2.3-17). A nonsignificant elevation in the relative risk was observed for aplastic anemia. The data suggest that infectious mononucleosis may confer a long-term increase in the risk of agranulocytosis. However, the association was an unexpected one, identified in the course of multiple comparisons, and it must be independently confirmed.

Clozapine-induced agranulocytosis. Incidence and risk factors in the United States

BACKGROUND

Clozapine is an atypical antipsychotic agent that is more effective than standard neuroleptic drugs in the treatment of patients with refractory schizophrenia. Unlike classic neuroleptic agents, clozapine is not associated with the development of acute extrapyramidal symptoms or tardive dyskinesia. The main factor limiting its use is the risk of potentially fatal agranulocytosis, estimated to occur in 1 to 2 percent of treated patients. After clozapine was approved by the Food and Drug Administration, it became available for marketing in the United States in February 1990 only as part of a special surveillance system (the Clozaril Patient Management System, or CPMS), in which a weekly white-cell count was required for the patient to receive a supply of the drug.

METHODS

We evaluated the CPMS data for February 1990 through April 1991 by survival analysis to determine the incidence of agranulocytosis and the effects of potential risk factors such as age and sex. Data were available for 11,555 patients who received clozapine during the period after marketing began.

RESULTS

Agranulocytosis developed in 73 patients, resulting in death from infectious complications in 2 patients. Episodes of agranulocytosis occurred in 61 patients within three months after they began treatment. The cumulative incidence of this side effect was 0.80 percent (95 percent confidence interval, 0.61 to 0.99) at 1 year and 0.91 percent (95 percent confidence interval, 0.62 to 1.20) at 1 1/2 years. The risk of agranulocytosis increased with age and was higher among women.

CONCLUSIONS

The occurrence of agranulocytosis is a substantial hazard of the administration of clozapine, but this hazard can be reduced by monitoring the white-cell count. The increasing risk of agranulocytosis with age and the reduced incidence after the first six months of treatment provide additional guidelines for the prescription and monitoring of clozapine treatment in the future.

Retrospective prevalence and incidence of drug-induced agranulocytosis in the city of São Paulo-Brasil

Retrospective study carried out in São Paulo, Brazil, from September 1981 through March 1990. During this period the study investigated 19,389 hematological patients, aiming to assess the prevalence and estimate the incidence of drug-induced agranulocytosis. To assess the Hematology Center's catch population, where the study took place, we adopted the incidence of hemophilia A, chronic myeloid leukemia and acute leukemia, described by the international literature as reference for our catch population estimate. Our findings revealed a prevalence of 1 case of agranulocytosis per 3,878 subjects treated at the São Paulo Hematology Center which translates into an incidence of 0.44 to 0.82 cases of agranulocytosis per million inhabitants, per year.

Sulfasalazine associated agranulocytosis in Sweden 1972-1989. Clinical features, and estimation of its incidence

During the 18 year period 1972-1989 a total of 62 cases of agranulocytosis associated with the use of sulphasalazine were reported to the Swedish Adverse Drug Reactions Advisory Committee (SADRAC). The median age of the patients was 52 y and median duration of sulphasalazine treatment was 43 days. The fatality rate was 6.5%, and among patients who recovered the median recovery time was 10 days. Twelve patients were treated concomitantly with other drugs generally suspected to induce agranulocytosis. From sales and prescription data the average incidence of agranulocytosis during sulphasalazine therapy was estimated to be 1/1750 patient years of exposure. From an ongoing Prescription Monitoring Project in a Swedish county it was possible to calculate the proportion of patients receiving sulphasalazine for different periods of time. The incidence of agranulocytosis during the first 30 days was estimated to be 1/2400 patients, while it was 1/700 between Days 31-90 and 1/11200 during Days 91-365. The risk of developing agranulocytosis during sulphasalazine treatment is considerable during the first three months of treatment, and the traditional way of expressing the risk (1/1750 patient years) underestimates the risk for the individual patient.

Agranulocytosis and aplastic anemia among Ramathibodi Hospital patients

A one-year prospective prevalence study on aplastic anemia and agranulocytosis was performed in Ramathibodi Medical School. A total of 91,581 complete blood counts were screened for potential cases of aplastic anemia and agranulocytosis according to defined criteria. Nineteen cases of aplastic anemia and five cases of agranulocytosis were found. The prevalence of the two conditions was discussed.

Descriptive epidemiology of agranulocytosis

BACKGROUND

To determine the incidence of agranulocytosis, a descriptive epidemiologic study was performed.

METHODS

With the use of computerized Medicaid billing data from 1980 through 1985 from Minnesota, Michigan, and Florida, the ratio of persons hospitalized with a discharge diagnosis of neutropenia to persons with any claim for medical service was first used as an estimate of the incidence rate of the condition. Patients with cancer and patients receiving cytotoxic and immunosuppressive drugs were excluded. The information provided by a review of medical records for a subset of neutropenia cases was used to determine the proportion with neutropenia after excluding cases with recurrent or chronic neutropenia, and to determine the proportion with agranulocytosis.

RESULTS

The incidence rates (95% confidence intervals) of agranulocytosis, excluding recurrent or chronic disease, were 2.3 (1.4 to 3.7), 7.7 (6.6 to 8.9), and 15.4 (11.3 to 20.4) per million per year in each state, respectively. The overall incidence was 7.2 (6.3 to 8.1) per million per year.

CONCLUSIONS

Agranulocytosis is an extremely uncommon condition. The excess risk of agranulocytosis due to any drug other than cytotoxic drugs must, therefore, be very low.

Clozapine-associated agranulocytosis: risk and aetiology

This paper reviews the epidemiology and pathogenesis of clozapine-associated agranulocytosis. According to present clinical experience, granulocytopenia can be expected in approximately 3% of patients during clozapine treatment. The risk of serious sequelae of granulocytopenia can be minimised by regular white blood cell count monitoring. Although research suggests that some patient groups may be at higher risk of developing this serious adverse reaction, we cannot yet predict the susceptible patients, so all patients exposed to clozapine should receive regular blood monitoring throughout treatment. Because of the risk of agranulocytosis, clozapine should only be used in schizophrenic patients who are resistant to, or intolerant of, conventional antipsychotic medications. Unless compliance with blood monitoring is assured, clozapine treatment should not be recommended.

Agranulocytosis associated with aprindine and other antiarrhythmic drugs: an epidemiological approach

The risk of agranulocytosis associated with anti-arrhythmic drugs has been assessed by studying previous drug exposure of all cases collected through a multicentre surveillance network in a defined geographical area during the period 1980-1988. One hundred and eighty-one patients with agranulocytosis (less than 500 granulocytes mm-3 at least in two different blood counts) were interviewed with a structured questionnaire. Eight cases attributable to anti-arrhythmic drugs were identified, all of them related to aprindine. Data on the consumption of several anti-arrhythmic drugs were identified, all of them related to aprindine. Data on the consumption of several anti-arrhythmic drugs (amiodarone, aprindine, quinidine, propafenone) were obtained in order to estimate the risk of agranulocytosis related with the previous use of these drugs. A relevant risk was identified only for aprindine, of the order of two cases per 1000 patient-years. Our data suggest that the risk of agranulocytosis associated with aprindine is lower than previously found.

Risks of agranulocytosis and aplastic anemia in relation to the use of cardiovascular drugs: The International Agranulocytosis and Aplastic Anemia Study

The risks of agranulocytosis and aplastic anemia in relation to the use of cardiovascular drugs were estimated in a population-based case-control study conducted in Israel and Europe (total population, 23 million). Cardiovascular drug use in the week before onset of illness was compared between 270 patients hospitalized with agranulocytosis and 1870 hospitalized control subjects. Propranolol (relative risk, 2.5), dipyridamole (3.8), digoxin (2.5), and acetyldigoxin (9.9) were significantly associated with agranulocytosis. The excess risks attributable to these drugs ranged from one to three cases per 10 million persons exposed for up to 1 week. Increased risks were also observed for cinepazide (used by six cases and no control subjects), procainamide (7, 1), and aprindine (5, 1); based on crude relative risk estimates, the excess risks for the latter two drugs were approximately three per million persons exposed for up to 1 week. The use of cardiovascular drugs in a 5-month period ending 1 month before hospital admission was compared between 152 patients with aplastic anemia and 2180 control subjects. Furosemide was the only significantly associated drug (relative risk, 3.1); the excess risk attributable to any exposure in a 5-month interval was 1.7 per million.

Drug-induced agranulocytosis: experience in two university hospitals

STUDY OBJECTIVE

to describe demographic data, offending drugs, clinical features, hematological profiles, clinical course, general outcome, factors influencing fatal result and microbiological aspects

DESIGN

Retrospective descriptive analysis

SETTING

Two university hospitals

PATIENTS

28 patients with 31 episodes of drug-induced agranulocytosis from Chulalongkorn Hospital (1976-1988) and 24 patients with 25 episodes from Songklanagarind Hospital (1983-1989)

RESULTS

Female exceeds male by ratio of 2.1:1, age ranged 15-73 years. The common drugs were antimicrobial agents, penicillins and sulfonamides; antithyroid drugs; antituberculous drugs and non-steroidal antiinflammatory drugs (NSAIDs), unidentified in 16 per cent. About 61 per cent occurred more than 14 days after drug exposure. The key presentations revealed fever, prostration and sorethroat. Two marrow appearances were recognised: left-shifted granulopoiesis with few or no mature forms (type-I) in 66 per cent; and the other, selective reduction of granulocytic precursors (type-II). Penicillins, sulfonamides, antithyroid drugs and NSAIDs were all related to type-I. The leukocyte count, neutrophil and monocyte numbers were significantly higher in type-I, as well much more rapid recovery time (mean +/- SD, 4.4 +/- 1.5 vs 12.4 +/- 14.1 days, p = 0). The possible sites of infection were identified in 59 per cent, the major ones were oral cavity and GI tract. The organisms were isolated in 58 per cent from the primary sites and 25 per cent from hemocultures, of which Pseudomonas aeruginosa was the most common. The case fatality rate is 12.5 per cent. The dead victims had the higher age, and strongly association with type-II marrow appearance (p = 0.038).

Mianserin and agranulocytosis in New Zealand

The frequency with which agranulocytosis was associated with mianserin in New Zealand was calculated, by two methods, from spontaneous reports to the Intensive Medicines Monitoring Programme (IMMP)--one gave a frequency of 1 in 1354 (95% CI 1 in 3145 to 1 in 685) and the other gave a rate of 1 in 1743 (95% CI 1 in 2895 to 1 in 1116). There were 3 deaths. Age and dose seemed to be related to occurrence of agranulocytosis. The frequency of the complication seemed to be higher than that reported for other countries, perhaps because higher doses were prescribed in New Zealand but also perhaps because of a selection bias in surveys elsewhere. The occurrence of agranulocytosis with mianserin in New Zealand is higher than that of white-cell dyscrasias reported with use of chloramphenicol, phenylbutazone, and oxyphenbutazone, and although the case-fatality rate of agranulocytosis is lower with mianserin than with the other drugs, the overall mortality rate may be higher.

The incidence of agranulocytosis during treatment of dermatitis herpetiformis with dapsone as reported in Sweden, 1972 through 1988

During the 17-year period 1972 through 1988, a total of seven cases of agranulocytosis associated with the use of dapsone for the treatment of dermatitis herpetiformis were reported in Sweden. The median age of the patients involved was 61 years; three of them were male. The median duration of dapsone treatment was 7 weeks and the daily prescribed dose was 100 mg. Based on sales and prescription data, the crude relative risk of agranulocytosis during dapsone treatment of dermatitis herpetiformis was 50, and the total risk was one case per 3000 patient years of exposure to dapsone. In relation to the number of new cases of dermatitis herpetiformis, agranulocytosis was estimated to develop in 1 of 240 to 425 patients receiving dapsone therapy. Patients should be instructed to seek medical care immediately in case of fever.

Nebulized amphotericin B as prophylaxis against invasive aspergillosis in granulocytopenic patients

The efficacy of inhaled amphotericin B in prevention of invasive aspergillosis in patients with granulocytopenia (granulocytes less than 0.5 X 10(9)/l for greater than 10 days) was investigated over a 12-month period. Amphotericin B prophylaxis was administered twice daily for the period of granulocytopenia to 34 patients who were at risk during 144 episodes of granulocytopenia. The cohort at risk was compared with historical controls. In the 2 years prior to institution of prophylaxis, 14 patients (11.4% of those at risk) developed invasive aspergillosis. All cases occurred whilst the patients were nursed on the open wards. Aspergillosis did not develop in 25 granulocytopenic patients nursed in single rooms with HEPA filtration. Since institution of prophylaxis, there have been no cases of invasive aspergillosis. These data suggest that nebulized amphotericin B may be useful in preventing invasive pulmonary aspergillosis in granulocytopenic patients, especially those nursed on the open wards, and warrants further investigation.

[Empirical treatment of febrile episodes in granulocytopenic patients with a combination of piperacillin and ofloxacin. Preliminary study]

We evaluated the efficacy and toxicity of piperacillin-ofloxacin as an empiric treatment of fever in patients with neutropenia. 24 febrile episodes occurring in 21 patients (mean neutropenia: 204/mm3) were treated. The neutropenia was due to an hematologic malignancy in 6 cases and to chemotherapy in 15 cases. Fever was related to septicemia in 4 cases, urinary tract infection in 1 case, other infectious sites without microbiological documentation in 11 cases, and was of unknown origin in 8 cases. Empirical therapy was started within 24 hours of the occurrence of fever greater than 38.5 degrees C with the combination of intravenous piperacillin (12 g/day in 3 divided doses) and oral ofloxacin (400 mg/day in 2 doses). The overall response rate was 86% (19/22) of evaluable cases, with an immediate success rate (apyrexia within 48 hours) of 46%. Of the 3 failures, one was bacteriologically documented and was due to a multiply resistant strain of Staphylococcus haemolyticus (to which both piperacillin and ofloxacin were resistant). The therapy was clinically well tolerated in all except 3 patients, in whom intolerance to intravenous piperacillin was observed, leading to discontinuation of the drug in 2 cases. More extensive and comparative trials should better determine the place of this piperacillin-ofloxacin combination as first-line treatment of febrile episodes in patients with neutropenia.

Agranulocytosis and significant leucopenia with neuroleptic drugs: results from the AMUP program

In the Federal Republic of Germany adverse drug reactions (ADR) have been continuously assessed at the departments of Psychiatry of Berlin and Munich since May 1979. About 13,000 neuroleptic-treated inpatients were monitored until August 1988. Approximately 1100 patients were exposed to clozapine, 6800 to haloperidol and 6000 to perazine, the two most frequently used neuroleptic drugs. In this 9-year period seven cases of agranulocytosis were observed, all in women. One case occurred with clozapine in monotherapy, the other six with perazine, three times in monotherapy, once in combination with trimethoprim/sulfamethoxazole and in one case each in combination with tricyclic antidepressants. Significant leucopenia (less than or equal to 3000/mm3) was observed in an additional eight cases. On four occasions each butyrophenones (twice in combination with TCA) and tricyclic neuroleptics (once in combination with TMS) were involved. The number of exposed patients per drug is too small for calculation of statistically valid incidence rates, especially in view of the frequent polypharmacy. The course of agranulocytosis was benign in all seven cases and required no other treatment than drug withdrawal in three cases. The early detection by regular WBCs is supposed to be mainly responsible for this and is therefore recommended at weekly intervals. This measure of safety appears most important for all medium potency tricyclic neuroleptics. As to treatment of agranulocytosis, additional measures (antibiotics, intensive medical care) depend upon the severity of the clinical picture.

Behavior of the exposure odds ratio in a case-control study when the hazard function is not constant over time

In case-control studies of adverse drug effects there is rarely much evidence to support the assumption that the hazard function among users is constant during therapy. Nonetheless, this assumption is often implicitly made. We will use both clinical reasoning and a simple model to show how non-constancy of the hazard function affects odds ratio interpretation. When the hazard function is non-constant and there is more than one temporal pattern of drug usage, the odds ratio will estimate a weighted mean of incidence ratios with weights dependent on the corresponding fractions of person-time. If the duration-specific incidence ratios differ widely, the odds ratio will depend not only on the drug but also on its usage pattern in the study population. This may explain some of the large regional odds ratio variation for dipyrone-related agranulocytosis in the International Agranulocytosis and Aplastic Anemia Study (JAMA 1986; 256: 1749-1757.

Drug-induced agranulocytosis

Agranulocytosis is a rare but potentially serious adverse side effect of many drugs. Although it was recognised as an idiosyncratic type of drug reaction more than 50 years ago, its pathogenesis is still not fully understood. Drug-related antibodies are responsible for the neutropenia in the so-called 'immune' or 'aminopyrine' type of agranulocytosis. In contrast to former assumptions, the disappearance of leucocytes is not only due to rapid destruction of circulation cells, but it can result also from failure of the production of granulopoetic cells. In some other groups of drugs there is no evidence of immune-mediated disease, but direct toxicity to bone marrow cells has been observed using biochemical methods or inhibition of the growth of granulopoetic colonies in semisolid culture media. Until now it has not been possible to define the enzymatic abnormality which could explain this metabolic type of idiosyncrasy. The quantification of the incidence of potentially drug-induced agranulocytosis in general, and in particular its association with single drugs, requires studies on large populations and the use of strict epidemiological methodology to prevent reporting of grossly biased results. Data from recent case control studies show definitely lower risks for some relevant groups of drugs than formerly appreciated. As expected, agranulocytosis has been observed in association with some recently introduced drugs. This underlines the necessity for continued postmarketing monitoring of potential haematological side effects and for further case control studies to furnish data to aid prescribing physicians and health authorities in decision-making.

Incidence of aplastic anemia: the relevance of diagnostic criteria. By the International Agranulocytosis and Aplastic Anemia Study

The incidence of aplastic anemia was estimated in a 4-year study conducted in Israel and seven areas in Europe. Strict definition criteria were used, and all data and bone marrow specimens were reviewed by a panel of experienced hematologists. Complete ascertainment of cases was attempted by establishing a telephone network including all relevant hospitals in the study areas. The incidence of aplastic anemia was estimated to be less than three per million per year, a figure lower than previously reported. The most likely explanation for the differences among studies is variation in diagnostic criteria, which might lead to an overestimation of the incidence in some previous studies.

Analgesic use, blood dyscrasias, and case-control pharmacoepidemiology. A critique of the International Agranulocytosis and Aplastic Anemia Study

The International Agranulocytosis and Aplastic Anemia Study (IAAAS) of analgesic-induced risks of blood dyscrasias represents the current "state of the art" in case-control pharmacoepidemiology. We present a conceptual framework for examining the goal, methods, and analysis of an epidemiologic study of drug risks and review the IAAAS within this framework. In our view, the new risk estimates reported by the IAAAS are not inherently more accurate than existing ones, nor have they been measured in clinically and sociodemographically relevant groups of patients over the anticipated course of therapy. Thus, the reported risks cannot be used to guide clinical or regulatory decisions concerning available treatment options for such patients. Furthermore, we believe that the IAAAS methods for selection of cases and controls, ascertainment of exposure, and data analysis may well have led to invalid estimates even for those risks that are reported. We hope that closer attention to the conceptual framework we suggest and the methodologic issues we raise will enable future case-control pharmacoepidemiologic studies to provide more useful and accurate answers to questions concerning the adverse effects of drugs.