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

Clinical presentation and management of drug-induced agranulocytosis

OBJECTIVE

In this article, we report and discuss the clinical presentation and management of idiosyncratic drug-induced agranulocytosis (neutrophil count <0.5 × 10(9)/l).

RESULTS/CONCLUSIONS

Idiosyncratic drug-induced agranulocytosis remains a potentially serious adverse event owing to the frequency of severe sepsis with severe deep tissue infections (e.g., pneumonia), septicemia and septic shock in approximately two-thirds of all hospitalized patients. However, several prognostic factors have recently been identified that may be helpful in practice to identify 'susceptible' patients. Old age (>65 years), septicemia or shock, metabolic disorders such as renal failure and a neutrophil count below 0.1 × 10(9)/l are currently consensually accepted as poor prognostic factors. In this potentially life-threatening disorder, modern management with broad-spectrum antibiotics and hematopoietic growth factors (particularly granulocyte colony-stimulating factor) is likely to improve prognosis. Thus, with appropriate management, the mortality rate from idiosyncratic drug-induced agranulocytosis is currently approximately 5%.

Incidence and risk factors of aplastic anemia in Latin American countries: the LATIN case-control study

Background Associations between aplastic anemia and numerous drugs, pesticides and chemicals have been reported. However, at least 50% of the etiology of aplastic anemia remains unexplained.

DESIGN AND METHODS

This was a case-control, multicenter, multinational study, designed to identify risk factors for agranulocytosis and aplastic anemia. The cases were patients with diagnosis of aplastic anemia confirmed through biopsy or bone marrow aspiration, selected through an active search of clinical laboratories, hematology clinics and medical records. The controls did not have either aplastic anemia or chronic diseases. A total of 224 patients with aplastic anemia were included in the study, each case was paired with four controls, according to sex, age group, and hospital where the case was first seen. Information was collected on demographic data, medical history, laboratory tests, medications, and other potential risk factors prior to diagnosis.

RESULTS

The incidence of aplastic anemia was 1.6 cases per million per year. Higher rates of benzene exposure (>/=30 exposures per year) were associated with a greater risk of aplastic anemia (odds ratio, OR: 4.2; 95% confidence interval, CI: 1.82-9.82). Individuals exposed to chloramphenicol in the previous year had an adjusted OR for aplastic anemia of 8.7 (CI: 0.87-87.93) and those exposed to azithromycin had an adjusted OR of 11.02 (CI 1.14-108.02). Conclusions The incidence of aplastic anemia in Latin America countries is low. Although the research study centers had a high coverage of health services, the underreporting of cases of aplastic anemia in selected regions can be discussed. Frequent exposure to benzene-based products increases the risk for aplastic anemia. Few associations with specific drugs were found, and it is likely that some of these were due to chance alone.

Drug use and aplastic anaemia: the French experience. French Cooperative Group for the Epidemiological Study of Aplastic Anaemia

The cause of the rare and severe condition of aplastic anaemia is largely unknown, although certain drugs have been implicated as possible aetiological factors, mostly through the evidence of case reports. A case-control study was conducted in metropolitan France between 1985 and 1988 to investigate aetiological factors in aplastic anaemia. It was conducted in parallel with the establishment of a national register of the incidence of aplastic anaemia, which started in May 1984. The controls used in the study consisted of 2 hospitalized controls (i.e. patients admitted to hospital at the same time as the case) and a neighbour control named by the case. All three controls were matched for age and sex, and were interviewed by the same investigator as the case. A total of 147 cases, 287 hospitalized controls and 108 neighbour controls were interviewed. An association of varying degrees was noted between aplastic anaemia and the following conditions or treatments: clinical hepatitis during the past 6 months; history of chronic immune disorder (mainly rheumatoid arthritis); gold salts and D-penicillamine; colchicine and allo-thiopurinol; acetaminophen and salicylates. This survey confirmed the vanishing role of previously known toxic agents in the aetiology of aplastic anaemia. Some differences observed between the results of the present study and those published previously suggest that targeted studies on each category of drug according to specific disease areas should be initiated.

Non-chemotherapy drug-induced agranulocytosis

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

Update on the role of non-opioids for postoperative pain treatment

Non-opioids play an ever increasing role in the treatment of postoperative pain; either on their own for mild to moderate pain or in combination with other analgesic approaches, in particular opioids, as a component of multimodal analgesia. The analgesics paracetamol (acetaminophen) and dipyrone (metamizole) as well as compounds with an additional anti-inflammatory effect (non-selective non-steroidal anti-inflammatory drugs and selective cyclo-oxygenase-2 inhibitors) are used widely in the perioperative period. Paracetamol is gaining renewed interest in this setting due to its minimal adverse effects and recent availability in a parenteral preparation, but its benefits are insufficiently studied. Dipyrone continues to be used in many countries despite the ongoing debate on the incidence and relevance of its ability to cause agranulocytosis. Among the anti-inflammatory drugs, selective cyclo-oxygenase-2 inhibitors have the most supportive data for their beneficial effects as a component of multimodal analgesia and offer benefits with regard to their adverse effect profile.

Idiosyncratic drug-induced agranulocytosis: Update of an old disorder

In this paper, we review the literature on idiosyncratic drug-induced agranulocytosis, a rare but life-threatening potential adverse event of most drugs. Articles were identified through MEDLINE searches (1966-2005). Additional references were localized through a review of textbooks on hematology and internal medicine, and information gleaned from international meetings. Additional unpublished data from our cohort with drug-induced agranulocytosis at the University Hospital of Strasbourg, France, were also considered. Searches were done using the following key words: "agranulocytosis", "drug-induced agranulocytosis", and "idiosyncratic agranulocytosis" and were restricted to: English- and French-language, human subjects, clinical trial, review, and guidelines. All of the papers and abstracts were reviewed by at least two senior researchers who selected the data used in the study. What we found is that, over the last 20 years, the incidence of idiosyncratic drug-induced agranulocytosis has remained stable - 2.4-15.4 cases per million - despite the emergence of new causative drugs, mainly antibiotics, antiplatelet agents, and antithyroid drugs. To date, drug-induced agranulocytosis remains a serious adverse event due to the frequency of severe sepsis with severe deep infections (such as pneumonia), septicemia, and septic shock in about two-thirds of all patients. In this setting, old age (>65 years), septicemia or shock, metabolic disorders such as renal failure, and a neutrophil count below 0.1x10(9)/L are poor prognostic factors. Nevertheless, with appropriate management using pre-established procedures, with intravenous broad-spectrum antibiotic therapy, and hematopoietic growth factors, the mortality rate is currently around 5%. Given the increased life expectancy and subsequent longer exposure to drugs, as well as the development of new agents, health care professionals should be aware of this adverse event and its management.

Minimising the potential for metabolic activation in drug discovery

Investigations into the role of bioactivation in the pathogenesis of xenobiotic-induced toxicity have been a major area of research since the link between reactive metabolites and carcinogenesis was first reported in the 1930s. Circumstantial evidence suggests that bioactivation of relatively inert functional groups to reactive metabolites may contribute towards certain drug-induced adverse reactions. Reactive metabolites, if not detoxified, can covalently modify essential cellular targets. The identity of the susceptible biomacromolecule(s), and the physiological consequence of its covalent modification, will dictate the resulting toxicological response (e.g., covalent modification of DNA by reactive intermediates derived from procarcinogens that potentially leads to carcinogenesis). The formation of drug-protein adducts often carries a potential risk of clinical toxicities that may not be predicted from preclinical safety studies. Animal models used to reliably predict idiosyncratic drug toxicity are unavailable at present. Furthermore, considering that the frequency of occurrence of idiosyncratic adverse drug reactions (IADRs) is fairly rare (1 in 1000 to 1 in 10,000), it is impossible to detect such phenomena in early clinical trials. Thus, the occurrence of IADRs during late clinical trials or after a drug has been released can lead to an unanticipated restriction in its use and even in its withdrawal. Major themes explored in this review include a comprehensive cataloguing of bioactivation pathways of functional groups commonly utilised in drug design efforts with appropriate strategies towards detection of corresponding reactive intermediates. Several instances wherein replacement of putative structural alerts in drugs associated with IADRs with a latent functionality eliminates the underlying liability are also presented. Examples of where bioactivation phenomenon in drug candidates can be successfully abrogated via iterative chemical interventions are also discussed. Finally, appropriate strategies that aid in potentially mitigating the risk of IADRs are explored, especially in circumstances in which the structural alert is also responsible for the primary pharmacology of the drug candidate and cannot be replaced.

Ramiprii-induced Agranulocytosis Confirmed by a Lymphocyte Cytotoxicity Test

A 50-year-old man who had chronic renal failure presented with neutropenic fever four days after ramipril was initiated. Agranulocytosis due to other causes was ruled out after a bone marrow aspiration and biopsy examination were performed. A relationship between the drug and the adverse effect was suggested. It was established by a novel lymphocyte cytotoxicity test.

Life-Threatening Idiosyncratic Drug-Induced Agranulocytosis in Elderly Patients

Agranulocytosis is a life-threatening disorder in any age, but particularly so in elderly patients who are receiving, on average, a larger number of drugs than younger patients. Drug-induced agranulocytosis still remains a rare event, with an annual incidence rate of approximately 3-12 cases per million population. This disorder frequently occurs as an adverse reaction to drugs, particularly antibacterials, antiplatelet agents, antithyroid drugs, antipsychotics or antiepileptic drugs, and NSAIDs. Although patients experiencing drug-induced agranulocytosis may initially be asymptomatic, the severity of the neutropenia usually translates into the onset of severe sepsis that requires intravenous broad-spectrum antibacterial therapy. In this setting, haematopoietic growth factors have been shown to shorten the duration of neutropenia. Thus, with appropriate management, the mortality rate of idiosyncratic drug-induced agranulocytosis is now 5-10%. However, given the increased life expectancy and subsequent longer exposure to drugs, as well as the development of new agents, physicians should be aware of this complication and its management.

Spironolactone-induced agranulocytosis: a case report

A 43-year-old woman with liver cirrhosis and hepatocellular carcinoma was admitted for the chief problem of ascites. Laboratory data revealed a leukocyte count of 3.8 x 10(9)/L on the second day of admission. Spironolactone was prescribed for diuresis beginning on the third day. Routine blood tests on the tenth day disclosed marked leukopenia (1.8 x 10(9)/L). Four days later, the leukocyte count was still 1.8 x 10(9)/L and a differential count revealed agranulocytosis (neutrophils, 0.25 x 10(9)/L). Eight days after withdrawal of spironolactone, the leukocyte count returned to normal (leukocytes, 4.9 x 109/L; neutrophils, 1.76 x 10(9)/L). On review of the patient's clinical condition, concurrent medication, and previous reports, we highly suspected that this episode of agranulocytosis was caused by spironolactone. Unlike four previously reported cases, this one did not involve furosemide, which is reported to be associated with leukopenia and agranulocytosis.

Drug-induced myelosuppression : diagnosis and management

Myelosuppression is a common and anticipated adverse effect of cytotoxic chemotherapy. It is a potential but rare idiosyncratic effect with any other drug, but there is a recognised association with a number of higher-risk agents which justify additional vigilance. Genetic risk factors are being identified which may predispose individuals to this reaction with particular drugs. As marker tests become available, dose adjustment or alternative treatment choices may help to avoid more severe reactions. Myelosuppression is potentially life threatening because of the infection and bleeding complications of neutropenia and thrombocytopenia. Strategies for monitoring, early detection, diagnostic confirmation and appropriate supportive care are well developed for cytotoxic therapy. Developments in antimicrobial chemotherapy, blood product transfusion support and growth factor therapy have improved outcomes. These advances are largely applicable to idiosyncratic drug-induced myelosuppression, reinforcing the importance of early recognition and referral to appropriate expertise. Many reactions will resolve on drug withdrawal with appropriate supportive care during the period of cytopenia. Prolonged marrow failure may require more specific treatment with intensive immunosuppression or consideration of bone marrow transplantation.

Adverse effects of observational studies when examining adverse outcomes of drugs: case-control studies with low prevalence of exposure

OBJECTIVES

The case-control study is commonly used to examine adverse drug events, in which prevalence of exposure in the source population is frequently very low. The objective of the current study was to examine the bias inherent in the odds ratio assessing the association between exposure and an adverse outcome when prevalence of exposure in the source population is extremely low.

DESIGN

Monte Carlo simulations examined the effect of sample size, exposure prevalence, and magnitude of the underlying odds ratio on the bias of the estimated risk ratio, and the power to detect a non-zero risk ratio.

RESULTS

Once the underlying odds ratio was at least four, the adverse effects of low prevalence of exposure was minimal. Studies with small sample sizes and low prevalence of exposure, coupled with small to moderate effect sizes, can result in biased estimates of association between exposure and disease status. With a sample size of 200 and an exposure prevalence of 0.5% in the control population, the bias in the estimated odds ratio can be as large as 115%. However, bias becomes negligible as sample size becomes large (n > or = 2000), even when prevalence of exposure is very low. Once the expected number of exposed controls is at least eight, the bias in the estimated odds ratio was no more than 5%.

CONCLUSIONS

Studies with small sample sizes and low prevalence of exposure, coupled with small to moderate effect sizes can result in biased estimates of association between exposure status and adverse drug effects. However, bias becomes negligible as sample size becomes large.

Antihypertensive drugs and the risk of idiopathic aplastic anaemia

AIMS

A recent report has raised concern that nifedipine may be associated with an increased risk of aplastic anaemia. This large population-based study evaluated the risk of idiopathic aplastic anaemia in users of calcium channel blockers compared with that of other antihypertensive drugs.

METHODS

The study was based on information derived from the General Practice Research Database. We conducted a follow-up study with a nested case-control analysis of 322 448 subjects who received antihypertensive drugs. Cases were people who had a first-time diagnosis of aplastic anaemia during January 1, 1988 through September 30, 1997. The risk estimate of aplastic anaemia was calculated for all antihypertensive drugs. For the nested case-control analysis, six controls were matched to each case on age, sex and general practice attended. Odds ratios compared the risk of idiopathic aplastic anaemia for all antihypertensive drugs relative to nonusers.

RESULTS

There were 13 cases of newly diagnosed idiopathic aplastic anaemia. The estimated risk of aplastic anaemia per 100 000 users was 0.8 (95% CI 0.1, 4.7) for calcium channel blockers, 1.4 (95% CI 0.5, 4.1) for beta-adrenoceptor blockers, 2.3 (95% CI 0.6, 8.6) for angiotension-converting enzyme (ACE) inhibitors and 5.9 (95% CI 1.6, 21.5) for users of other antihypertensive drugs. In the case-control analysis of 13 cases and 77 controls, the odds ratio was 0.3 (95% CI 0.02, 3.3) for calcium channel blockers, 0.5 (95% CI 0.1, 2.5) for beta-adrenoceptor blockers, 0.7 (95% CI 0.1, 5.6) for ACE inhibitors, 1.2 (95% CI 0.1, 11.8) for users of other antihypertensive drugs and 0.7 (95% CI 0.1, 7.2) for users of multiple drugs with a calcium channel blocker compared with nonusers.

CONCLUSIONS

The present study suggests that the use of calcium channel blockers is not associated with an increased risk of aplastic anaemia.

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.

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.

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.

Diclofenac-associated thrombocytopenia and neutropenia

OBJECTIVE

To report a case of thrombocytopenia and a case of neutropenia, both associated with the use of diclofenac.

CASE SUMMARIES

A 63-year-old woman was receiving diclofenac for osteoarthritis. During a hospital admission for pneumonia, she was found to have severe thrombocytopenia. Diclofenac therapy was stopped and the thrombocytopenia resolved. Several months later she was inadvertently treated with diclofenac by another physician and again experienced thrombocytopenia, which again resolved on discontinuation of the drug and has not recurred since. A 72-year-old man was receiving diclofenac for 9 months for osteoarthritis. He was then found to have asymptomatic neutropenia. Diclofenac therapy was stopped and the neutropenia resolved with no other intervention. He was not rechallenged.

DISCUSSION

Severe thrombocytopenia and neutropenia are extremely rare adverse reactions to diclofenac. To date, there is only 1 case of each that is well documented and supported in the literature.

CONCLUSIONS

Severe thrombocytopenia and neutropenia are potential serious adverse effects of the use of diclofenac. Patients who are receiving diclofenac and develop symptoms of either thrombocytopenia or neutropenia should have a complete blood count, and if this diagnosis is confirmed, the drug therapy should be stopped.

Double-blind study with dipyrone versus tramadol and butylscopolamine in acute renal colic pain

To investigate the combined analgesic and spasmolytic effect of dipyrone, 104 patients suffering from "severe" or "excruciating" colic pain due to a confirmed calculus in the upper urinary tract were randomized to receive i.v. either 2.5 g dipyrone (36 patients), 100 mg tramadol (35 patients), or 20 mg butylscopolamine (33 patients) in a multicentre, observer-blind, parallel-group study conducted in 8 German centres. The three treatment groups were homogeneous when analyzed by age, sex, height, and baseline pain intensity. Dipyrone was significantly more effective than tramadol in reducing pain for the primary endpoint, pain intensity differences (PID) at 20, 30, and 50 min after drug administration, and was significantly more effective than butylscopolamine at 30 and 50 min for the secondary efficacy endpoint, pain intensity differences on a categorical scale. Dipyrone had the highest SPID0-2 h of the three drugs (P < 0.05). Only 5 patients receiving dipyrone needed "rescue" medication as compared with 13 patients given tramadol and 11 patients receiving butylscopolamine. Adverse events were observed in 4 patients receiving butylscopolamine and in 1 patient each given dipyrone and tramadol. "Distinct" pain relief as assessed on a visual analogue scale (VAS) is a reliable method of determining the onset of analgesic action in the colic pain model.

Treatment of fever in childhood

Although the need for routine antipyretic therapy in children has often been questioned, there are no data to contra-indicate this. Not all fevers need to be treated but many physicians do so to relieve parental concern. The most commonly used antipyretic drugs are acetylsalicylic acid (ASA), paracetamol (acetaminophen) and dipyrone (metamizol). Paracetamol and ASA have been extensively evaluated but there are few clinical trials on dipyrone. In the last decade a strong statistical association has been observed between salicylates and Reye syndrome. Paracetamol is the most common cause of acute hepatic failure. Dipyrone has been associated with agranulocytosis. In the light of these findings the extensive use of antipyretics drugs has been seriously questioned.

Propafenone associated agranulocytosis

Propafenone hydrochloride was approved for marketing by the United States (U.S.) Food and Drug Administration (FDA) in November 1989. During U.S. clinical trials of propafenone, one case of agranulocytosis was seen. Seven additional cases have been reported outside the U.S. One German report of profound but reversible granulocytopenia appeared in 1982. In January 1991, the FDA reviewed adverse events reported with propafenone. Four reports of agranulocytosis were identified and are described. The reporting rate of approximately one case of agranulocytosis per 10,000 propafenone prescriptions per year likely underestimates the true incidence of this adverse event.