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

Nonchemotherapy drug-induced agranulocytosis in children detected by a prospective pharmacovigilance program

OBJECTIVES

A prospective evaluation of nonchemotherapy drug-induced agranulocytosis (DIA) cases, which are infrequent in the pediatric population. We characterize agranulocytosis cases and assess lab test differences between drug- and nondrug-induced agranulocytosis.

METHODS

Through our Prospective Pharmacovigilance Program from Laboratory Signals at Hospital we detected pediatric agranulocytosis cases from July 2007 to December 2010. This program estimates the incidence, drug causality, clinical features, outcomes of DIA pediatric cases, and assesses laboratory differences with respect to non-DIA.

RESULTS

We detected 662 agranulocytosis in 308 pediatric patients, of which 14 were caused by nonchemotherapy drugs. The incidence rate of DIA for 10,000 pediatric patients was 3.92 (Poisson 95% confidence interval 1.09-8.77); 78.6% of DIA cases occurred in patients younger than 3 years. The final outcome was recovery without sequela in all cases. The pharmacologic group most frequently implicated was antimicrobial drugs (11 drugs), 7 of which were beta-lactams. The drugs most frequently suspected were cefotaxime and vancomycin (3 cases each). We found 3 drugs (cloperastine, codeine, and enoxaparin) not previously described to induce DIA. Automatic linear modeling (n = 56, R² = 45.2%) showed a significant inverse association with platelets (R² = 17.5%), hemoglobin, and alanine transaminase, and a direct association with red cell distribution (R² = 16.2%). A generalized linear model (Type III, n = 1188; DIA, n = 86; likelihood ratio chi-squared = 156.16) retained eosinophils (p <.001), platelets (p <.001), total serum proteins (p <.001), and hemoglobin (p =.039).

CONCLUSIONS

We found a higher incidence of DIA in children than previously described. Our findings also suggest an immune-mediated destruction or myeloid toxicity, possibly facilitated by an increase in drug exposure.

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.

Agranulocytosis associated with dipyrone (metamizol)

OBJECTIVES

Reported estimates of the risk of agranulocytosis associated with metamizol have varied by several orders of magnitude. We assessed this association in a large database for the surveillance of blood dyscrasias.

METHODS

Since 1980, all laboratory units of haematology in a defined area (3.3-4.1x10(6) inhabitants) contribute to the ascertainment of all cases of agranulocytosis meeting strict diagnostic criteria. These cases of patients with agranulocytosis and sex-, age-, hospital- and date-matched controls were interviewed using a structured questionnaire about previous drug exposures, and relative risks were calculated for several categories of exposure to metamizol.

RESULTS

After a total follow-up of 78.73x10(6) person-years, 273 community cases of agranulocytosis had been found--of which 96 were excluded for various reasons and 177 were included in the case-control analysis--and were compared with 586 matched controls. Thirty cases of agranulocytosis (16.9%) and nine controls (1.5%) had been exposed to metamizol during the week before the index day. The adjusted relative risk was 25.8 [95% confidence interval (CI), 8.4-79.1], and the attributable incidence was 0.56 (0.4-0.8) cases per million inhabitants and per year. The risk disappeared after more than 10 days since the last dose of metamizol, and it increased with duration of use. Those with agranulocytosis exposed to metamizol had taken the drug for longer periods than the exposed controls. Compared with the cases recently reported from Sweden, the duration of use of metamizol by our exposed cases was substantially shorter, and the use of concomitant medications potentially causing agranulocytosis was lower.

DISCUSSION

In our milieu, agranulocytosis attributable to metamizol is rare. Geographical disparities in its risk estimate can be partly explained by differences in its patterns of use, in terms of dose, duration and concomitant medications.

Case-population studies in pharmacoepidemiology

The case-population approach aims at providing a risk estimate by comparing the incidence of the disease of interest among those exposed to the drug under study with the incidence among the non-exposed. For that purpose, the cases with the disease of interest have to be ascertained independently of the exposure status. Their rate and pattern of exposure have to be ascertained by interview with a structured questionnaire. Information on the patterns and the prevalence of drug consumption is needed in order to estimate the rate of exposure, and drug consumption statistics can be used to this end. In this paper, we review the main characteristics of studies using this approach or a similar one, and studies where series of cases exposed to the drug of interest were compared with drug consumption statistics. We looked at selected basic methodological requirements. Most of the studies reviewed suffer from incomplete case ascertainment, inaccurate definition of the disease of interest, incomplete information on exposures and other risk factors, and/or limited control of potential confounding, among other limitations. All the reviewed studies had several limitations regarding the estimation of the population at risk. The methods used in case-population studies should be clearly described, particularly with respect to the identification of the cases (numerator) and the estimation of the consumption prevalence (denominator). Case-population studies can give approximate risk estimates, but the method should be validated by comparing its results with those of case-control studies.

Possible association between ocular chloramphenicol and aplastic anaemia--the absolute risk is very low

AIMS

To determine whether topical ocular chloramphenicol increases the risk of aplastic anaemia and to estimate the magnitude of this risk, if any.

METHODS

Population-based prospective case-control surveillance of aplastic anaemia in a community of 4.2 million inhabitants from 1980 to 1995 (67.2 million person-years) plus case-population estimate of the risk, based on sales figures of ocular chloramphenicol in the study area during the study period.

RESULTS

One hundred and forty-five patients with aplastic anaemia and 1,226 controls were included in the analysis. Three cases (2.1%) and 5 controls (0.4%) had been exposed to ocular chloramphenicol during the relevant etiological period. The adjusted odds ratio was 3.77 (95% confidence interval, 0.84-16.90). Two cases had also been exposed to other known causes of aplastic anaemia. The incidence of aplastic anaemia among users of ocular chloramphenicol was 0.36 cases per million weeks of treatment. The incidence among non users was 0.04 cases per million weeks.

CONCLUSIONS

An association between ocular chloramphenicol and aplastic anaemia cannot be excluded. However, the risk is less than one per million treatment courses.

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.

Adverse drug reactions leading to hospital admission

This article describes the implementation of a simple method of drug surveillance set up at a hospital emergency ward. From a total of 48,678 patients admitted, the medical records of those presenting with one or more of a pre-established list of admission diagnoses (n = 7728; 15.8%) were checked. Of these 554 (1.1%) were diagnosed as experiencing an adverse drug reaction. When the medical record suggested an adverse drug reaction, drugs taken before admission were ascertained by interviewing the patients with a structured questionnaire. After excluding upper gastrointestinal bleeding (226 cases) and certain bone marrow blood dyscrasias (42 cases), 286 patients with drug-induced events leading to hospital admission were identified in 2 years. Fatal adverse drug reactions, previously undescribed reactions, and some specific examples, such as digoxin-amiodarone interaction, drug-induced pancreatitis, nicardipine-induced AV block, severe skin reactions, and NSAID-induced bronchospasm, are described. Basically, this method consists of assembling series of cases systematically, and is therefore devoid of selective bias. In addition, it allows a more in-depth clinical and anamnesic study of specific diseases, as compared with voluntary reporting.