The incidence of dipyrone-induced agranulocytosis in Greece during 1975

Efficacy of metamizole versus ibuprofen and a short educational intervention versus standard care in acute and subacute low back pain: a study protocol of a randomised, multicentre, factorial trial (EMISI trial)

INTRODUCTION

Low back pain (LBP) is among the top three most common diseases worldwide, resulting in a life with pain-related disability. To date, no study has assessed the efficacy of metamizole (dipyrone), a non-opioid analgesic and antipyretic prodrug compared with the conventional non-steroidal anti-inflammatory drug ibuprofen, in patients with an acute LBP episode. Further, it is unclear, whether a short educational intervention is superior to usual care alone.

OBJECTIVES

The objective of this study is to assess first, whether metamizole is non-inferior to ibuprofen in a new episode of acute or subacute LBP. Second, we aim to assess whether a short educational intervention including evidence-based patient information on the nature of LBP is superior to usual care alone.

METHODS AND ANALYSIS

An investigator-initiated multicentre, randomised, double blind trial using a factorial design will be performed. A total of 120 participants with a new episode of LBP will be recruited from GP practices, outpatient clinics and from emergency departments, and randomised into four different treatment groups: ibuprofen alone, ibuprofen and short intervention, metamizole alone, metamizole and short intervention. The primary endpoint for the medical treatment will be change in pain assessed on an 11-point Numeric Rating Scale after 14 days. The primary outcome for the short intervention will be change in the Core Outcome Measures Index assessed after 42 days.

ETHICS, DISSEMINATION AND FUNDING

This study has been approved by the responsible Ethics Board (Ethikkommission Bern/2018-01986) and the Swiss Agency for Therapeutic Products (Swissmedic/2019DR4002). Results will be published in open access policy peer-reviewed journals. The study is funded by the Swiss National Science Foundation (grant number 32 003B-179346).

TRIAL REGISTRATION NUMBER

NCT04111315.

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.

Safety of Calcium Dobesilate in Chronic Venous Disease, Diabetic Retinopathy and Haemorrhoids

The aim of the present review is to consider the adverse effects and the safety profile of calcium dobesilate. Calcium dobesilate (Doxium) is a veno-tonic drug, which is widely prescribed in more than 60 countries from Europe, Latin America, Asia and the Middle East for three main indications: chronic venous disease, diabetic retinopathy and the symptoms of haemorrhoidal attack. Data sources used for this review comprise the international literature (1970-2003), a postmarketing surveillance (PMS) report for calcium dobesilate from OM Pharma (Geneva, Switzerland) covering the period 1974-1998, and periodic safety update reports (PSUR) covering the period 1995-2003 from the French Regulatory authorities pharmacovigilance database and OM Pharma. Data from the PMS report for 1974-1998 indicated that adverse events with calcium dobesilate did not occur very frequently and had the following distribution in terms of frequency: fever (26%), gastrointestinal disorders (12.5%), skin reactions (8.2%), arthralgia (4.3%), and agranulocytosis (4.3%). No deaths were attributed to calcium dobesilate in the PMS report. Using data on product use in the Swiss Compendium we estimated the prevalence of agranulocytosis to be 0.32 cases/million treated patients, i.e. ten times less than the calculated prevalence of agranulocytosis in the general population. Most adverse events are type B, i.e. rare and unrelated to the pharmacological properties of calcium dobesilate. This review concludes that the risk of an adverse effect with calcium dobesilate 500-1500 mg/day is low and constant over time. The recently raised problem of agranulocytosis (a total of 13 known cases drawn from all data sources) appears to be related to methodological bias. Such a review reinforces the need for a strong international pharmacovigilance organisation using similar methods to detect and analyse the adverse effects of drugs.

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.

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.

Fournier's gangrene after hemorrhoidectomy: association with drug-induced agranulocytosis. Report of a case

An unusual case of Fournier's gangrene after hemorrhoidectomy and drug-induced agranulocytosis, as the predisposing condition, is described. The patient had severe granulocytopenia that was attributed to the recent use of dipyrone. Together with hemodynamic resuscitation, broad-spectrum antibiotic and recombinant human granulocyte colony-stimulating factor were started. Wide surgical excision of all the gangrenous tissues, in addition to laparoscopic formation of a defunctioning sigmoid loop colostomy, was performed. The white blood cell count rose steadily and the patient experienced a rapid recovery. We emphasize that radical surgery must be accompanied by pharmacologic interventions for a successful outcome in such cases.

[Immuno-allergic thrombopenias and leukopenias induced by drugs]

Certain types of cytopenia are due to the destruction of blood cells by an antibody, active only in conjunction with a drug which has previously provoked sensitivity in patients when administered in standard doses. Drug-induced thrombocytopenia and leucopenia of allergic origin are relatively rare. They produce characteristic symptoms, i.e. brutal onset and acute development of the disease; healing takes place when the drug in question is withdrawn. Haematological diseases of drug-related aetiology are being brought to light by serological methods which detect the specific antibody for the drug responsible for the accident. The physiopathological mechanism is still not clearly elucidated.

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.