Drug-induced agranulocytosis: evidence for the commitment of bone marrow haematopoiesis

Ceftriaxone-Induced Neutropenia Successfully Treated With Alternative β-Lactam Antibiotics: A Case Report and Review of the Literature

Ceftriaxone-induced neutropenia is a rare and severe adverse effect of the drug. It usually resolves in one to three weeks following the cessation of ceftriaxone and the administration of granulocyte colony-stimulating factor (G-CSF). After neutrophil recovery, patients are often treated with non-β-lactam antibiotics instead of ceftriaxone due to the possibility of cross-reactivity associated with β-lactam allergy. However, in some cases, β-lactam antibiotics are superior to non-β-lactam antibiotics. Few cases of the readministration of β-lactam antibiotics for patients who developed ceftriaxone-induced neutropenia have been reported so far. Moreover, its pathogenesis and management have still not been established. We describe a case of successful readministration of β-lactam antibiotics for a patient who had developed ceftriaxone-induced neutropenia. A 37-year-old man with a prosthetic aortic valve was admitted to our hospital with a fever. Blood culture on admission revealed methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia, and transesophageal echocardiography (TEE) showed aortic valve vegetation with multiple septic emboli seen on brain CT. We diagnosed MSSA infective endocarditis with central nervous complications. He underwent an operation and was treated with ceftriaxone. On admission day 28, he developed neutropenia (33/μL), and ceftriaxone-induced neutropenia was suspected. Vancomycin was started instead of ceftriaxone, and his neutrophil count recovered within two weeks with the administration of G-CSF. After recovery, on day 40 of admission, ampicillin sodium was administered instead of vancomycin. Although he developed mild eosinophilia, he did not exhibit neutropenia and was discharged with an amoxicillin prescription on day 60 of admission. Our report suggests the possibility that patients who develop ceftriaxone-induced neutropenia can be treated safely with an alternative β-lactam antibiotic, ampicillin sodium, without causing β-lactam cross-reactivity of neutropenia.

Medikamentös induzierte Knochenmarkveränderungen

Die zyto- und histomorphologische Untersuchung des Knochenmarks bei Blutbildungsstörungen muss immer auch die Möglichkeit medikamentös induzierter Veränderungen berücksichtigen. Diese können einzelne Differenzierungslinien oder das gesamte Knochenmark betreffen. Sie bestehen aus quantitativen Verschiebungen, d. h. einer Hypo- oder Hyperplasie und/oder Reifungsstörungen. Letztere umfassen eine mitunter extreme Linksverschiebung oder imitieren Vitaminmangelzustände und Atypien wie bei einem myelodysplastischen Syndrom (MDS). Auch die gesamte Hämatopoese kann betroffen sein, wobei im Extremfall das Bild einer aplastischen Anämie hervorgerufen wird. Das Spektrum infrage kommender Medikamente ist sehr breit und die Veränderungen in der Regel zu unspezifisch, um gezielt auf das schädigende Agens zurückzuschließen, was erst in Kenntnis der Medikamentenanamnese möglich wird. In der onkologischen Therapie eingesetzte zytotoxische Substanzen können mit einer durchschnittlichen Latenzzeit von 2–6 Jahren MDS auslösen, die allerdings bei Medikamenten, die in die DNA-Reparatur eingreifen, auch kürzer sein kann.

Rare case of pancrelipase therapy-induced neutropaenia

A 61-year-old man was transferred to our facility from an outside hospital due to refractory neutropaenia of unknown aetiology. The patient presented to the referring hospital with a 5-day history of worsening diarrhoea and abdominal pain. Initial lab results at presentation showed severe neutropaenia with an absolute neutrophil count of 0. Investigations included a bone marrow biopsy which showed slightly hypocellular marrow with near absence of granulocytic precursors. A CT without contrast showed evidence of chronic pancreatitis and acute colitis. The patient's neutropaenia persisted despite granulocyte colony-stimulating factor therapy. The patient was, thus, transferred to our facility for a higher level of care. At our facility, the patient had rapid correction of neutropaenia after discontinuation of pancrelipase therapy. The patient's abdominal pain and diarrhoea also improved while off pancrelipase. Neutropaenia has completely resolved 6 weeks after discharge without any further therapy.

Idiosyncratic Drug-Induced Neutropenia and Agranulocytosis in Elderly Patients

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

When should the clinician suspect a drug-induced blood dyscrasia, and how should he proceed?

Blood dyscrasias account for only a minor fraction of all adverse drug reactions (ADRs), but are relevant because of their relatively high morbidity and mortality. For the majority of drugs, the magnitude of risk is low enough to remain undetected until wider distribution of the drug takes place. Thus, only post-marketing studies, carried out with appropriate methodology and sufficient statistical power, will allow the risk of serious haematological side-effects of new drugs to be ascertained. Publication of carefully studied and thoroughly described single case studies and reports to registries are necessary to detect new associations between drugs and blood dyscrasias, while only large cohort or case-control studies are suited to quantify the risks. Physicians managing a newly detected blood dyscrasia should be aware that it may be drug-induced. They should assess the exact diagnosis, obtain and thoroughly document a detailed exposure history and follow the blood counts after withdrawal of all potentially relevant agents. The recognition and appropriate management of the problem in individual cases is the basis for both effective patient care and the quality of subsequent pharmaco-epidemiological evaluation.

Dipyrone-induced granulocytopenia: a case for awareness

Dipyrone, also known as metamizole, is an analgesic and antipyretic drug that was banned by the United States Food and Drug Administration because of its association with agranulocytosis. However, it is still produced and marketed in several countries in Central and South America as well as in Europe, Asia, and Africa. It can also be found in the United States, where illegal sales have been reported in California gift shops, markets, bakeries, and other retail establishments. Dipyrone is commonly found in the homes of families who are originally from areas where it is still lawfully marketed. We describe a patient who developed granulocytopenia and fever after taking dipyrone and discuss the available literature. Our aim is to raise awareness of this drug, which is commonly used outside the United States, and to call attention to its well-known and potentially lethal side effect.

Demonstration of drug-dependent antibodies in two patients with neutrophenia and successful treatment with granulocyte-colony-stimulating factor

BACKGROUND

Many drugs have been reported as being capable of inducing immune neutropenia, but the causative drug-dependent antibodies were rarely demonstrated.

STUDY DESIGN AND METHODS

This report describes the results of serologic testing and treatment in two children with immune neutropenia related to cefotaxime and metamizole, respectively. Serum samples were tested in the presence and the absence of the drugs using the granulocyte agglutination test (GAT), the granulocyte immunofluorescence test (GIFT), and the monoclonal antibody-specific immobilization of granulocyte antigens (MAIGA) assay.

RESULTS

The serum of one child contained cefotaxime-dependent antibodies that were detectable by the GAT and the MAIGA assay, but not by the GIFT. The serum of the other child gave positive reactions in the GAT and GIFT due to HLA antibodies and in the MAIGA assay only in the presence of metamizole. While cefotaxime-dependent antibody was directed against CD16, the metamizole antibody was directed against CD11b and CD35. The administration of granulocyte-colony-stimulating factor led to an abrupt increase in circulating neutrophils in both cases.

CONCLUSION

The use of more than one technique is necessary for detection of drug-dependent antibodies against neutrophils, and early administration of granulocyte-colony-stimulating factor may result in fewer complications in these patients.

Nonchemotherapy drug-induced agranulocytosis: a review of 118 patients treated with colony-stimulating factors

To determine the role of growth factors in nonchemotherapy drug-induced agranulocytosis, we reviewed 118 published reports of administration of colony-stimulating factors for the disorder. Main outcomes were total duration of neutropenia and mortality. The mean time to neutrophil recovery was 4.6 +/- 3.2 days and 7.7 +/- 5.1 days in patients with a granulocyte count at diagnosis of 0.1-0.5 x 10(3)/mm3 and less than 0.1 x 103/mm3, respectively. The mortality rate was 4.2%. Without therapy with growth factors, the mean time to neutrophil recovery after discontinuation of the offending agent was reported to be 10 +/- 8 days. The mortality rate was 16% in one study. We conclude that hematopoietic growth factors may shorten the duration of neutropenia and reduce mortality in patients with severe drug-induced agranulocytosis.

Spironolactone-induced agranulocytosis

OBJECTIVE

To report a case of agranulocytosis secondary to spironolactone in a patient with cryptogenic liver disease.

CASE SUMMARY

A 58-year-old Hispanic woman with cryptogenic cirrhosis was admitted to University Hospital on October 31, 1995. Laboratory data revealed a leukocyte count of 1.0 x 10(3)/mm3 and an absolute neutrophil count (ANC) of 10 cells/mm3. Prior to treatment with spironolactone, the leukocyte count was 10.2 x 10(3)/mm3 and ANC 8400 cells/mm3. Agranulocytosis resolved 5 days following the discontinuation of spironolactone. Results from the bone marrow biopsies before and after treatment with spironolactone suggested that agranulocytosis was caused by the drug's toxic effect on the bone marrow.

DISCUSSION

Drug-induced agranulocytosis is a serious adverse effect, occurring at a rate of approximately 6.2 cases per million persons each year. In addition to the case reported here, three other reports of agranulocytosis secondary to spironolactone have been published in the literature. Several factors have been identified that may increase a patient's risk for developing agranulocytosis, including increased age, hepatic or renal impairment, drug dosage and duration, and concurrent medications.

CONCLUSIONS

Agranulocytosis secondary to spironolactone is a serious potential adverse effect. Patients with risk factors for developing this adverse effect should be closely monitored since early detection and discontinuation of spironolactone can improve prognosis.

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.

Granulocyte-colony stimulating factor for sulfasalazine-induced agranulocytosis

OBJECTIVE

To report a case of sulfasalazine-induced agranulocytosis that was successfully treated with granulocyte-colony stimulating factor (G-CSF).

CASE SUMMARY

An 82-year-old woman developed agranulocytosis within two months of initiating sulfasalazine therapy. She was hospitalized, empiric antibiotic and antifungal agents were prescribed, and sulfasalazine therapy was stopped. The patient received G-CSF 600 micrograms/d subcutaneously for six consecutive days, starting on hospital day 5. Agranulocytosis resolved on day 5 and leukopenia on day 6 of G-CSF therapy. No adverse reactions were attributed to administration of this agent and the patient was discharged on hospital day 13.

DISCUSSION

Numerous agents, including sulfasalazine, have been associated with agranulocytosis. Agranulocytic patients frequently experience life-threatening bacterial and fungal infections. Administration of colony stimulating factors may reduce the duration of agranulocytosis and incidence of life-threatening infections.

CONCLUSIONS

G-CSF administration appears to have decreased the duration of this elderly patient's agranulocytosis and hospitalization.

Treatment of drug-induced agranulocytosis with recombinant granulocyte colony-stimulating factor (rh G-CSF)

Five patients with drug-induced agranulocytosis received 300 micrograms recombinant human granulocyte colony-stimulating factor (rh G-CSF) subcutaneously twice daily for 2-5 days. G-CSF therapy resulted in a steep increase of the neutrophil count, which was faster than that in patients with spontaneous recovery reported in the literature. In all four patients with infectious complications fever rapidly declined with the increase of granulocytes. G-CSF may be useful in the management of drug-induced agranulocytosis.

Human immune toxicity

This review examines xenobiotic toxicity to the immune system, stressing in particular those aspects of most relevance to humans. Immunotoxicity is examined especially from three points of view: by what immunological component is affected, by classes of foreign agents that adversely affect the human immune system and by critical evaluation of human case reports and epidemics. Mechanisms by which xenobiotics interrupt cytokine networks are emphasized. The concept that microbial agents, both environmental as well as infectious, may act as immunotoxicants, either alone or in synergism with conventional agents is introduced. Instances of human immunotoxicology are critically evaluated in terms of clinical relevance, i.e. whether increased susceptibility to opportunistic infections or tumor emergence takes place in the affected individuals.

The growth capacity of hematopoietic progenitor cells in severe neutropenia induced by famotidine

In four cases of severe neutropenia of unknown origin we found a strong inhibition of the growth of granulocyte-macrophage (GM) progenitor cells. The development of GM colonies in culture (GM-CFU-c) was more than 80% reduced in comparison to the control group. In particular, the interleukin 3-(IL-3) and granulocyte macrophage colony-stimulating factor-(GM-CSF) dependent growth was affected; a combination of growth factors (IL-3, GM-CSF, and G-CSF, the granulocyte colony-stimulating factor) resulted in a less reduced growth. The findings were primarily compatible with drug-induced bone marrow failure. Among the medications given to the patients, famotidine, an H2-receptor blocker, was discussed as an agent which possibly triggers off this process. After the withdrawal of famotidine, in three cases a continual increase of the growth of GM precursors was detected, reaching the normal level 7-17 days later. In one case, further investigations of the progenitor cells could not be carried out due to the death of the patient, but the rapid increase of neutrophils in the peripheral blood after withdrawal of famotidine pointed to the recovery of hematopoiesis. In vitro studies showed that famotidine, depending on the dose, inhibits the single growth factor-dependent colony growth (IL-3, GM-CSF, or G-CSF) of bone marrow progenitors from a concentration as low as 10 micrograms/ml. With the combination of all three growth factors only slight inhibitory effects were detectable (up to 150 micrograms/ml famotidine). These results indicate that famotidine, in common with other H2-receptor antagonists, can affect hematopoietic progenitor cells. However, the plasma concentration of famotidine normally used in ulcer therapy does not seem to influence the hematopoiesis. Apparently, the progenitor cells of only a few patients possess a higher sensitivity to the blockade of H2-receptors at this concentration of famotidine. This was demonstrated in one case (patient 3) 2 years after the patient had recovered from famotidine-induced neutropenia. The growth of peripheral myeloid, erythroid, and multilineage progenitor cells of this patient was remarkably reduced even at famotidine concentrations of 0.1-5.0 micron/ml whereas in the control group no inhibition was detected at these famotidine concentrations. Again, the IL-3-dependent colony formation was more affected than in the case of the combination of IL-3, GM-CSF, and G-CSF. After the removal of accessory cells the inhibitory effect of famotidine persisted, demonstrating that accessory cells do not play a major role in this process.

The role of leukocyte-generated reactive metabolites in the pathogenesis of idiosyncratic drug reactions

Evidence strongly suggests that many adverse drug reactions, including idiosyncratic drug reactions, involve reactive metabolites. Furthermore, certain functional groups, which are readily oxidized to reactive metabolites, are associated with a high incidence of adverse reactions. Most drugs can probably form reactive metabolites, but a simple comparison of covalent binding in vitro is unlikely to provide an accurate indication of the relative risk of a drug causing an idiosyncratic reaction because it does not provide an indication of how efficiently the metabolite is detoxified in vivo. In addition, the incidence and nature of adverse reactions associated with a given drug is probably determined in large measure by the location of reactive metabolite formation, as well as the chemical reactivity of the reactive metabolite. Such factors will determine which macromolecules the metabolites will bind to, and it is known that covalent binding to some proteins, such as those in the leukocyte membrane, is much more likely to lead to an immune-mediated reaction or other type of toxicity. Some reactive metabolites, such as acyl glucuronides, circulate freely and could lead to adverse reactions in almost any organ; however, most reactive metabolites have a short biological half-life, and although small amounts may escape the organ where they are formed, these metabolites are unlikely to reach sufficient concentrations to cause toxicity in other organs. Many idiosyncratic drug reactions involve leukocytes, especially agranulocytosis and drug-induced lupus. We and others have demonstrated that drugs can be metabolized by activated neutrophils and monocytes to reactive metabolites. The major reaction appears to be reaction with leukocyte-generated hypochlorous acid. Hypochlorous acid is quite reactive, and therefore it is likely that many other drugs will be found that are metabolized by activated leukocytes. Some neutrophil precursors contain myeloperoxidase and the NADPH oxidase system, and it is likely that these cells can also oxidize drugs. Therefore, although there is no direct evidence, it is reasonable to speculate that reactive metabolites generated by activated leukocytes, or neutrophil precursors in the bone marrow, could be responsible for drug-induced agranulocytosis and aplastic anemia. This could involve direct toxicity or an immune-mediated reaction. These mechanisms are not mutually exclusive, and it may be that both mechanisms contribute to the toxicity, even in the same patient. In the case of drug-induced lupus, a prevalent hypothesis for lupus involves modification of class II MHC antigens.(ABSTRACT TRUNCATED AT 400 WORDS)

Drug-induced agranulocytosis: prognostic factors in a series of 168 episodes

The prognostic value of 36 clinical and analytical parameters at diagnosis in patients with drug-induced agranulocytosis was analysed in an adult population. This multicentre, retrospective study examined possible prognostic factors by multiple logistic regression analysis in a series of 168 clinical episodes. The overall mortality was 16%. Renal insufficiency at diagnosis and the development of bacteraemia were associated with a poor prognosis. Advanced age, decreased leucocyte count, lymphocytopenia, bone marrow myeloid hypoplasia, increased percentage of bone marrow plasma cells and shock were found to be associated with a poor prognosis only in the univariate analysis. An independent analysis of the myeloid cellularity at diagnosis showed an inverse correlation with the time to recovery of the granulocyte counts (r = -0.43; P = 0.001). Our data indicate that despite some important clinical differences (higher incidence of infections of the oropharynx, shorter period of neutropenia and almost exclusive presence of gram-negative organisms), the infections complicating the treatment of cancer patients have the same prognostic features than those seen in patients with acute agranulocytosis. Therefore the established therapeutic guidelines for neutropenia after cancer chemotherapeutic agents are applicable to patients with acute agranulocytosis.

Granulocyte-macrophage colony stimulating factor for the treatment of drug induced agranulocytosis

Drug induced agranulocytosis is an uncommon but potentially fatal complication. In some cases, it may be associated with hypoplasia and depletion of granulocytic precursors in the marrow, leading to prolonged neutropenia. We report on the use of granulocytic-macrophage colony stimulating factor (GM-CSF) in two such cases, at a dose of 10 micrograms per kilogram per day subcutaneously. The absolute neutrophil count rose above 500/mm3 in 3 days in both cases. We believe that GM-CSF expedited the recovery of granulocyte counts in our patients and warrants further study in the management of drug induced neutropenia.

Transient pancytopenia. A report from the International Agranulocytosis and Aplastic Study

From a population-based study on the incidence of potentially drug-associated blood dyscrasias 28 cases were identified with pancytopenia. Who recovered within 90 days after diagnosis. Early recovery occurred more frequently in patients showing normal or increased cellularity of the bone marrow than in patients with bone marrow hypoplasia. Median recovery times of leukocytes were 14 and 10 days and of platelets 21 and 9 days in patients with and without bone marrow hypoplasia, respectively. Age and sex distribution were similar in both groups. Of 28 patients, 11 reported a period of fever before onset of pancytopenia. Sixteen patients in whom information on drug use was available had taken a median of 4 drugs before the onset of symptoms that were related to pancytopenia. From these results we present the hypothesis that transient pancytopenia with or without marrow hypoplasia can be the expression of the same type of bone marrow injury and that drugs or viral infections should be considered as etiological factors.

Drug metabolism by leukocytes and its role in drug-induced lupus and other idiosyncratic drug reactions

This review presents a unifying hypothesis that provides a connection between several types of hypersensitivity reactions associated with several types of drugs and explains some of the therapeutic effects (antiinflammatory activity and antithyroid effects) of these same drugs. This hypothesis centers on the oxidation of these drugs to chemically reactive metabolites by peroxidases. The drugs of interest have functional groups that are easily oxidized. The major peroxidase involved in this hypothesis is MPO because of its critical location in leukocytes which play a key role in the function of the immune system. However, thyroid peroxidase can probably also oxidize many of the same drugs to reactive metabolites, and this may be responsible for the thyroid autoimmunity observed in connection with some hypersensitivity reactions. Peroxidases have also been described in the skin and in platelets, and their presence may be responsible for the high incidence of skin reactions in the hypersensitivity response and the occurrence of immune-mediated thrombocytopenia, respectively. Involvement of other peroxidases, such as prostaglandin peroxidase, may also be important for antiinflammatory effects of drugs. In addition, leukocytes contain prostaglandin synthetase, and the activation of leukocytes leads to the release of arachidonic acid and the production of prostaglandins. This process may also lead to the metabolism of drugs to reactive metabolites. In studies of the metabolism of procainamide and dapsone, aspirin and indomethacin did not inhibit the formation of the hydroxylamine by neutrophils and mononuclear leukocytes. This is evidence against the involvement of prostaglandin synthetase in these oxidation; however, preliminary studies with other drugs suggest that prostaglandin synthetase may contribute to the metabolism of some drugs by leukocytes. Furthermore, the metabolism of phenylbutazone, phenytoin, and tenoxicam, as well as our preliminary work with other drugs such as carbamazepine, suggests that the range of drugs that are metabolized to reactive metabolites by peroxidases may be broader than initially suspected. There are several other drugs that do not fit into the functional group classes covered in this review but have similar properties. A good example is alpha-methyldopa, which is associated with drug-induced lupus, immune-mediated hemolytic anemia, and other hypersensitivity reactions. Such drugs may also be metabolized to reactive metabolites by peroxidases. Another aspect of the hypothesis is that an infection, or other inflammatory condition, may be an important risk factor for a hypersensitivity reaction because such a stimulus leads to activation of leukocytes which can lead to formation of reactive metabolites from certain drugs.(ABSTRACT TRUNCATED AT 400 WORDS)

Agranulocytosis associated with "Mexican aspirin" (dipyrone): evidence for an autoimmune mechanism affecting multipotential hematopoietic progenitors

A case of acute, transient agranulocytosis and thrombocytopenia associated with ingestion of dipyrone is reported. This once widely used analgesic, which is now banned in the United States, was obtained by the patient as "aspirin" while traveling in Mexico. Studies of the effects of this patient's serum on purified CD34+ marrow cells, which were highly enriched for hematopoietic progenitors, showed not only a drug-dependent suppression of the in vitro growth of myeloid progenitors, as has been reported previously, but also a drug-dependent suppression of primitive multipotential progenitors (CFU-Mix) and erythroid progenitors (BFU-E). These findings indicate that autoimmune, antibody-hapten interactions which have been reported to occur in dipyrone- and aminopyrine-induced agranulocytosis are not restricted to the neutrophil lineage.

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.

Acute gingival necrosis caused by drug-induced agranulocytosis

A case of acute gingival necrosis, which was caused by drug-induced agranulocytosis, is reported. The patient had classic signs and symptoms, and the treatment of oral lesions was symptomatic. Regeneration of the gingival mucosa was almost complete 20 days after the onset of the disease.

Toxic effects of the histamine H(2) receptor antagonist metiamide on bone-marrow haemopoietic and stromal progenitor cells in vitro

The histamine H(2)-receptor antagonist, metiamide has been shown to cause agranulocytosis in vivo. In vitro colony forming assays for bone-marrow stromal fibroblast progenitors (CFU-F) and granulocyte/macrophage progenitor cells (CFU-GM) were performed, using murine bone marrow, to assess the relative sensitivity of committed haemopoietic cells, and the marrow stromal microenvironment to metiamide toxicity. CFU-F were more susceptible than CFU-GM to inhibition by metiamide, with 50% inhibition of colony formation (ID(50)) at 17 and 180 mug/ml in the CFU-F and CFU-GM assays, respectively. Inhibition of CFU-GM required the continuous presence of the drug, while CFU-F were inhibited similarly by either short-term (20-hr) or prolonged (10-day) incubation with metiamide (ID(50) 27 and 17 mug/ml, respectively). It is suggested that bone-marrow stromal cell damage may be an important contributory factor in the haemopoietic toxicity of metiamide.