Probable Vancomycin-Induced Neutropenia

Vancomycin-Induced Neutropenia With Subsequent Perioperative Readministration: A Case Report

Vancomycin (VCM), an essential antibiotic for antimicrobial-resistant Gram-positive cocci, can lead to complications such as neutropenia. Here, we present a case of a 25-year-old male with noncommunicating hydrocephalus due to an intraventricular tumor who developed neutropenia during VCM therapy. Despite the suspected VCM-induced neutropenia, short-term readministration was deemed necessary for perioperative infection prophylaxis. This patient was readministered without neutropenia. A review of the literature revealed an earlier onset of VCM-induced neutropenia than that previously reported, emphasizing the importance of vigilant monitoring. Although readministration of VCM in patients with neutropenia is uncommon, it may be feasible with careful risk assessment, particularly in cases of mild neutropenia and short-term therapy. However, the mechanisms underlying VCM-induced neutropenia remain unclear, necessitating further research on the optimal management strategies.

Hematological adverse events associated with anti-MRSA agents: a real-world analysis based on FAERS

This study investigated the patterns of hematological adverse events related to daptomycin (DAP), tigecycline (TIG), vancomycin (VAN) and linezolid (LIN) in the FDA Adverse Event Reporting System (FAERS). Adverse event associations were analyzed through calculating reporting odds ratio (ROR), proportional reporting ratio (PRR), multiple gamma Poisson shrinkage (MGPS), and Bayesian confidence propagation neural network (BCPNN). A comprehensive descriptive analysis was also conducted considering factors such as age, gender, daily dose, cumulative dose, and time to onset. The leading hematologic adverse events were eosinophilia for daptomycin, coagulation abnormalities and thrombocytopenia for tigecycline, thrombocytopenia, neutropenia, and anemia for linezolid, and thrombocytopenia, eosinophilia, and neutropenia for vancomycin. Most of the affected patients were over 55 years old. Daily doses for the tigecycline and daptomycin groups exceeded the standard daily dose. The times to onset were 14.00 days for daptomycin (interquartile range [IQR], 4.00-21.00), 6.00 days for tigecycline (IQR, 2.00-9.00), 10.00 days for linezolid (IQR, 4.00-16.5), and 10.00 days for vancomycin (IQR,5.00-20.00). It is essential to intensify early monitoring and identification of these adverse events, especially in the context of off-label dosages and for elderly patients and individuals taking medication for over one week.

Neutropenia, Thrombocytopenia, and Eosinophilia: An Unusual Triad in a Patient on Long-Term Vancomycin Therapy

Patient: Female, 46-year-old

Final Diagnosis: Adverse drug reaction • epidural abscess

Symptoms: Eosinophilia • neutropenia • thrombocytopenia

Medication: —

Clinical Procedure: —

Specialty: General and Internal Medicine

Evolving Role of Pharmacogenetic Biomarkers to Predict Drug-Induced Hematological Disorders

ABSTRACT

Drug-induced hematological disorders constitute up to 30% of all blood dyscrasias seen in the clinic. Hematologic toxicity from drugs may range from life-threatening marrow aplasia, agranulocytosis, hemolysis, thrombosis to mild leukopenia, and thrombocytopenia. Pathophysiologic mechanisms underlying these disorders vary from an extension of the pharmacological effect of the drug to idiosyncratic and immune-mediated reactions. Predicting these reactions is often difficult, and this makes clinical decision-making challenging. Evidence supporting the role of pharmacogenomics in the management of these disorders in clinical practice is rapidly evolving. Despite the Clinical Pharmacology Implementation Consortium and Pharmacogenomics Knowledge Base recommendations, few tests have been incorporated into routine practice. This review aims to provide a comprehensive summary of the various drugs which are implicated for the hematological adverse events, their underlying mechanisms, and the current evidence and practical recommendations to incorporate pharmacogenomic testing in clinical care for predicting these disorders.

Clinical and Pharmacokinetic Outcomes of Peak-Trough-Based Versus Trough-Based Vancomycin Therapeutic Drug Monitoring Approaches: A Pragmatic Randomized Controlled Trial

Background

Vancomycin therapeutic drug monitoring (TDM) is based on achieving 24-h area under the concentration–time curve to minimum inhibitory concentration cure breakpoints (AUC₂₄/MIC). Approaches to vancomycin TDM vary, with no head-to-head randomized controlled trial (RCT) comparisons to date.

Objectives

We aimed to compare clinical and pharmacokinetic outcomes between peak–trough-based and trough-only-based vancomycin TDM approaches and to determine the relationship between vancomycin AUC₂₄/MIC and cure rates.

Methods

A multicentered pragmatic parallel-group RCT was conducted in Hamad Medical Corporation hospitals in Qatar. Adult non-dialysis patients initiated on vancomycin were randomized to peak–trough-based or trough-only-based vancomycin TDM. Primary endpoints included vancomycin AUC₂₄/MIC ratio breakpoint for cure and clinical effectiveness (therapeutic cure vs therapeutic failure). Descriptive, inferential, and classification and regression tree (CART) statistical analyses were applied. NONMEM.v.7.3 was used to conduct population pharmacokinetic analyses and AUC₂₄ calculations.

Results

Sixty-five patients were enrolled [trough-only-based-TDM (n = 35) and peak–trough-based-TDM (n = 30)]. Peak–trough-based TDM was significantly associated with higher therapeutic cure rates compared to trough-only-based TDM [76.7% vs 48.6%; p value = 0.02]. No statistically significant differences were observed for all-cause mortality, neutropenia, or nephrotoxicity between the two groups. Compared to trough-only-based TDM, peak–trough-based TDM was associated with less vancomycin total daily doses by 12.05 mg/kg/day (p value = 0.027). CART identified creatinine clearance (CL_CR), AUC₂₄/MIC, and TDM approach as significant determinants of therapeutic outcomes. All patients [n = 19,100%] with CL_CR ≤ 7.85 L/h, AUC₂₄/MIC ≤ 1256, who received peak–trough-based TDM achieved therapeutic cure. AUC₂₄/MIC > 565 was identified to be correlated with cure in trough-only-based TDM recipients [n = 11,84.6%]. No minimum AUC₂₄/MIC breakpoint was detected by CART in the peak–trough-based group.

Conclusion

Maintenance of target vancomycin exposures and implementation of peak–trough-based vancomycin TDM may improve vancomycin-associated cure rates. Larger scale RCTs are warranted to confirm these findings.

Agranulocytosis Induced by Vancomycin. Case Report and Literature Review

Patient: Male, 38

Final Diagnosis: Agranulocytosis induced by Vancomycin

Symptoms: Fever • pain

Medication: Vancomycin

Clinical Procedure: Antibiotic treatment

Specialty: Hematology

Spondylodiscitis in Paediatric Patients: The Importance of Early Diagnosis and Prolonged Therapy

Background: Spondylodiscitis (SD), the concurrent infection of a vertebral disc and the adjacent vertebral bodies, is a very severe disease that can lead to death or cause spinal deformities, segmental instabilities, and chronic pain, which significantly reduces the quality of life for affected patients. Early diagnosis and treatment are essential in order to reduce the risk of negative outcomes. The two cases of SD that are described in this paper might be useful for informing paediatric approaches to children with SD. Case presentation: The cases that are reported here are about two children of approximately 2 and 3 years of age, in whom SD involving the L4⁻L5 and L3⁻L4 interspaces, had a subacute or chronic course. The clinical manifestations were mild, fever was absent, and the lumbar pain lasted for a long time and was the predominant symptom. Moreover, laboratory tests were in the normal range or only slightly abnormal, as were the standard radiographs of the lumbar spine. In both of the cases, SD confirmation was obtained through magnetic resonance imaging (MRI) and MRI was also used to evaluate the response to therapy. In both of our patients, tuberculosis was excluded based on tuberculin skin testing and the Quantiferon TBgold tests being negative. This finding led to the prescription of a broad-spectrum antibiotic therapy, including a drug that was potentially effective against Staphylococcus aureus (Sa). The strict monitoring of the spinal damage with MRI avoided the need for aspirations or biopsies; invasive procedures that are ethically acceptable in pediatric age only in a few selected cases, when the empirical antibiotic is associated with a worsening of spinal damage; or the vertebral osteomyelitis lesion mimics a tumoral lesion. Conclusions: Although rare, SD represents an important disease in children. In toddlers and preschool children, it can have a subacute or chronic course, in which only back pain, irritability, and walking difficulties are the signs and symptoms of the disease. MRI remains the best method for confirming the diagnosis and for evaluating therapy efficacy. Antibiotics are the drugs of choice. Although the duration has not been established, antibiotics should be administered for several weeks.

Glycopeptide-Induced Neutropenia: Cross-Reactivity Between Vancomycin and Teicoplanin

Objective:

To report teicoplanin-related neutropenia that developed after an episode of neutropenia induced by vancomycin therapy.

Case Summary:

A 57-year-old female suffered from osteomyelitis of the left humerus, with a white blood cell (WBC) count of 2.8 × 103/mm3 and absolute neutrophil count (ANC) of 0.28 × 103/mm3, occurring after 24 days of vancomycin therapy. Vancomycin was changed to teicoplanin and the agranulocytosis resolved 4 days later. However, a new episode of neutropenia, with a WBC count of 2.8 × 103/mm3 and ANC of 0.448 × 103/mm3, occurred 11 days after teicoplanin initiation. Agranulocytosis resolved 4 days following withdrawal of teicoplanin.

Discussion:

Because of the close time relationship between drug administration and the development of symptoms and signs, as well as between drug withdrawal and changes in WBC count and ANC, the episodes of neutropenia were suspected to be drug related. Teicoplanin-induced agranulocytosis that followed vancomycin-induced agranulocytosis suggests a possible cross-reactivity between the 2 drugs. Both reactions were categorized as probable according to the Naranjo probability scale.

Conclusions:

For all patients with vancomycin-induced neutropenia, possible cross-reactivity of teicoplanin should be monitored.

Epidemiology of Vancomycin-Induced Neutropenia In Patients Receiving Home Intravenous Infusion Therapy

Background:

Vancomycin is frequently used to manage serious resistant gram-positive Infections. Neutropenia, whose epidemiology has not been well characterized, is a potentially serious adverse event associated with the use of vancomycin.

Objective:

To characterize the incidence and risk factors for development of vancomycin-induced neutropenia in patients treated with home intravenous vancomycin therapy.

Methods:

A retrospective chart review was conducted of adult patients receiving vancomycin therapy through the University of New Mexico Home Intravenous Infusion Clinic between January 1998 and December 2004. Data collection included demographics, comorbid conditions, dose and duration of vancomycin therapy, indications for vancomycin use, vancomycin concentrations, all concurrent medications, laboratory data, culture and susceptibility data, reasons for antibiotic alteration or discontinuations, all other recorded adverse events, management of adverse events, and outcomes of adverse events.

Results:

A total of 372 charts of patients managed through the clinic were reviewed and 114 patients treated with vancomycin were identified. Fourteen (12%) cases of vancomycin-induced neutropenia were identified; 4 (3.5%) cases included a reduction in absolute neutrophil count to 500 cells/mm3 or less. The mean ± SD duration of vancomycin therapy and time to neutropenia were 32 ± 29 and 26 ± 15 days, respectively. Laboratory monitoring was performed on a weekly basis and resolution of vancomycin-induced neutropenia occurred promptly after discontinuation. Total vancomycin doses used and serum concentrations were not associated with the development of neutropenia.

Conclusions:

Vancomycin-induced neutropenia may occur at a higher frequency than previously reported. Clinicians should monitor hematologic parameters at least weekly in patients receiving home intravenous vancomycin therapy.

Nonchemotherapy drug-induced neutropenia and agranulocytosis: could medications be the culprit?

Drug-induced agranulocytosis is a severe complication that has been implicated with most classes of medications. Medications such as clozapine, trimethoprim-sulfamethoxazole and methimazole have been more commonly associated with agranulocytosis than other agents. Although the pathogenesis isn't fully elucidated, it appears to be two-fold with a direct toxicity to the myeloid cell line and immune-mediated destruction. Patients may be asymptomatic at the time neutropenia is discovered or may present with more severe complications such as sepsis. In approximately 5% of cases drug-induced agranulocytosis may be fatal. Management of drug-induced agranulocytosis includes the immediate discontinuation of the offending medication, initiation of broad-spectrum antibiotics and consideration of the use of granulocyte colony-stimulating factors in high-risk patients.

Severe neutropenia following a prolonged course of vancomycin that progressed to agranulocytosis with drug reexposure

OBJECTIVE

To report a case of severe neutropenia after discontinuing prolonged treatment with vancomycin that progressed to agranulocytosis with vancomycin reexposure.

CASE SUMMARY

A 78-year-old woman presented with severe neutropenia (absolute neutrophil count [ANC] 37 cells/μL) and hypocellular bone marrow with absence of myeloid elements 8 weeks after discontinuing a 3-week treatment course of vancomycin 750 mg every 12 hours. Filgrastim 300 μg daily was started for neutropenia and vancomycin 750 mg every 12 hours and aztreonam 1 g every 8 hours were initiated for catheter-related acute thrombophlebitis of the upper extremity. The patient's ANC decreased to 10 cells/μL within 3 days of starting vancomycin. We suspected an autoimmune process, potentially related to vancomycin exposure, and began treatment with methylprednisolone 1 mg/kg daily. The ANC precipitously dropped to 0 cells/μL despite treatment with steroids and an increased filgrastim dose of 480 μg/day. All antibiotics were discontinued on the fifth day of hospitalization. Within 48 hours, her neutrophil count showed recovery (white blood cell count 500 cells/μL; 10% neutrophils).

DISCUSSION

Idiosyncratic drug-induced agranulocytosis is an uncommon phenomenon but is often associated with serious consequences such as sepsis. We believe this case is unique because of the unusually late neutropenia discovered several weeks after finishing a prolonged course of vancomycin. Furthermore, agranulocytosis developed after unintentional rechallenge with vancomycin. According to the Naranjo probability scale, this case illustrates a probable adverse event caused by vancomycin.

CONCLUSIONS

This case demonstrates a serious adverse event potentially associated with vancomycin use, and calls attention to the safety of rechallenging with vancomycin during a possible drug-induced neutropenia.

Vancomycin-induced neutropenia: is it dose- or duration-related?

OBJECTIVE

To systematically evaluate the literature to determine whether vancomycin-induced neutropenia is dose- or duration-related and provide clinicians with feasible treatment alternatives.

DATA SOURCES

A literature search of PubMed (1949-November 2010), MEDLINE (1950-November 2010), EMBASE (1980-November 2010), and International Pharmaceutical Abstracts (1970-November 2010) was performed using the terms vancomycin, neutropenia, and leukopenia. Citations from publications were reviewed for additional references.

STUDY SELECTION AND DATA EXTRACTION

Studies and case reports were included if they reported neutropenia with vancomycin administration and excluded if they did not describe vancomycin dosages and/or concentrations, or if neutropenia resolved while the patient was still receiving vancomycin. Cases with significant confounders and those in which authors provided minimal information about patients were also excluded.

DATA SYNTHESIS

Seven retrospective chart reviews (ie, case series) and 33 case reports were identified. Of these, 3 retrospective reviews and 26 case reports met inclusion criteria. To our knowledge, no prospective studies have assessed this clinical complication. Data suggest that vancomycin-induced neutropenia may not be completely related to daily dosages, total cumulative dosage, or supratherapeutic vancomycin concentrations. Furthermore, evidence suggests that neutropenia is more likely associated with therapy longer than 7 days, with the majority of episodes occurring beyond 20 days of therapy. Given these findings, a practical approach is to monitor white blood cell (WBC) count with a differential (including absolute neutrophil count) once a week in patients who are receiving vancomycin for more than 7 days.

CONCLUSIONS

Vancomycin-induced neutropenia is most likely associated with prolonged vancomycin exposure. Patients receiving vancomycin for longer than 7 days should have WBC count, differential, monitored weekly. Vancomycin should be discontinued if there is a high clinical suspicion of it causing neutropenia, and an alternative agent should be initiated. Prospective case-controlled studies are needed to better characterize this adverse event.

Tolerability of teicoplanin in 117 hospitalized adults with previous vancomycin-induced fever, rash, or neutropenia: a retrospective chart review

BACKGROUND

Vancomycin has reliable antibacterial activity against many gram-positive pathogens but is associated with many adverse events. Teicoplanin, another glycopeptide, is associated with fewer adverse events, but its use in patients with previous vancomycin-induced adverse reactions remains controversial.

OBJECTIVES

The aims of this work were to evaluate the clinical characteristics of hospitalized patients with vancomycin-induced fever (ie, drug fever), rash, or neutropenia and to examine the tolerability of teicoplanin in these patients.

METHODS

This was a retrospective review of the medical charts of patients aged >or=18 years who were hospitalized between January 2002 and October 2007 at National Cheng Kung University Hospital in Tainan, Taiwan. Patients were included if they experienced drug-induced fever (ie, "drug fever"), rash, or neutropenia during vancomycin treatment. Their antimicrobial therapy was subsequently switched to teicoplanin. Clinical information and the development of drug fever, rash, or neutropenia with teicoplanin were determined from the charts.

RESULTS

Antibiotic therapy was switched to teicoplanin in 117 patients with vancomycin-induced fever alone (n = 24), rash alone (n = 77), both drug fever and rash (n = 8), or neutropenia (n = 8). The mean (SD) age of these patients was 53.1 (22.8) years, and 65 (56%) were male. The major clinical indications for vancomycin therapy among these patients were wound infections (21%), respiratory tract infections (14%), and bacteremia (13%). The dosages for vancomycin ranged from 1 g every 5 days to 1 g BID, and for teicoplanin ranged from 400 mg daily to 400 mg q72h, adjusted by the degree of renal dysfunction. Overall, 12 patients with vancomycin-induced fever (n = 2), rash (n = 6), or neutropenia (n = 4) subsequently developed teicoplanin-induced fever (n = 3), rash (n = 3), or neutropenia (n = 6). Specifically, of 8 patients with vancomycin-induced neutropenia, 4 (50%) subsequently developed neutropenia after switching to teicoplanin. Vancomycin- and teicoplanin-induced neutropenia was often noted after 1 week of treatment. Among patients with vancomycin-induced fever, rash, or neutropenia, there were no differences between patients with or without teicoplanin-induced fever, rash, or neutropenia in terms of age, sex, weight, dosage or duration of vancomycin therapy, dosage of teicoplanin, or underlying disease. There was no difference in mortality rates between patients with or without teicoplanin-induced fever, rash, or neutropenia. The cause of all deaths was progression of infectious or underlying disease, unrelated to vancomycin or teicoplanin use.

CONCLUSIONS

Based on this retrospective chart review of hospitalized patients with vancomycin-induced fever, rash, or neutropenia, only 10% experienced subsequent teicoplanin-induced fever, rash, or neutropenia. However, it should be noted that half of the patients with vancomycin-induced neutropenia developed teicoplanin-induced neutropenia.

Management of complicated infections in the era of antimicrobial resistance: the role of tigecycline

BACKGROUND

Increasing antimicrobial resistance and infection complications pose challenges to optimal antibiotic therapy. Paucity of new antibiotics (and the eventual bacterial resistance they face) highlights the critical need for more appropriate use of broadly effective agents, which may help to thwart the dramatic rise in global resistance. Single agents that can be combined effectively with others, if needed, promise the simplest overall utility. Approved in 2005 to treat complicated skin and intra-abdominal infections, tigecycline is a novel extended-spectrum minocycline derivative that circumvents bacterial resistance, as it is unaffected by efflux pumps and ribosomal protection. However, tigecycline should not be used as empiric monotherapy for treatment of health-care associated infections known or suspected to be owing to Pseudomonas aeruginosa or Proteus spp.

OBJECTIVE

This article summarizes the demonstrated clinical utility of tigecycline so far.

METHODS

A MEDLINE search examined authoritative published clinical studies, reviews and case reports detailing the clinical record of tigecycline since 2004.

RESULTS/CONCLUSION

Tigecycline continues to maintain satisfactory profiles of safety, efficacy and antimicrobial resistance avoidance. Regardless, continued surveillance is needed to detect reduced susceptibility and resistance against both community and nosocomial pathogens. Judicious use of agents reserved for multidrug resistant pathogens is vital to preserve their effectiveness.

Cephalosporin-induced leukopenia following rechallenge with cefoxitin

OBJECTIVE

To describe a case of cefazolin-induced leukopenia in a critically ill patient who developed this adverse reaction upon rechallenge with cefoxitin.

CASE SUMMARY

A 22-year-old male was admitted after a motor vehicle crash. beta-Lactam therapy was initiated with vancomycin, cefepime, and metronidazole and, upon identification of methicillin-sensitive Staphylococcus aureus bacteremia 4 days later, therapy was narrowed to cefazolin 1 g every 12 hours. The dose was adjusted to 1 g every 12 hours during continuous venovenous hemodialysis. Imipenem was given for 2 days, resulting in a total of 18 days of beta-lactam treatment, at which time he developed significant leukopenia (white blood cell [WBC] count 0.9 x 10(3)/microL). Antimicrobial treatment was changed to tigecycline and continued for suspected pleural space infection. The patient's WBC count recovered within 4 days after the change in therapy. He was taken to surgery 8 days after cefazolin was discontinued and received perioperative prophylaxis with cefoxitin (total dose 3 g). Subsequently, the patient again became severely leukopenic (WBC count 2.4 x 10(3)/microL). Within a week after surgery, the patient developed septic shock secondary to multidrug-resistant Escherichia coli bacteremia and died.

DISCUSSION

beta-Lactam-induced leukopenia is a rare but well-described adverse drug reaction. It is a cumulative dose-dependent phenomenon reported to occur most often after 2 weeks of therapy. The mechanism of leukopenia is thought to be secondary to either an immune-mediated response or direct bone marrow toxicity. Rechallenge with a different beta-lactam antibiotic has not been shown to consistently cause recurrent leukopenia. The case described here suggests an immune-related mechanism for the development of leukopenia. Use of the Naranjo probability scale determined the association between cephalosporin use and leukopenia to be probable.

CONCLUSIONS

Cefazolin was a probable cause of this patient's leukopenia. It is important for clinicians to recognize beta-lactam-induced leukopenia and maybe recommend use of a drug from a different antibiotic class if continued treatment is indicated.

An overview of harms associated with beta-lactam antimicrobials: where do the carbapenems fit in?

The US Institute of Medicine's focus on patient safety has motivated hospital administrators to facilitate a culture of safety. As a result, subcommittees of the pharmacy and therapeutics committee have emerged in many hospitals to focus on adverse events and patient safety. Antimicrobial harms have gained the attention of practicing clinicians and hospital formulary committees, because they top the list of drugs that are associated with adverse events and because of certain serious harms that have ultimately led to the withdrawal of some antimicrobial agents. In the near future, several antimicrobials in the late phase of development will become available for clinical use (ceftobiprole, ceftaroline, and telavancin), and others (doripenem and dalbavancin) have recently joined the armamentarium. Because new antimicrobials will become part of the treatment armamentarium, it is important to discuss our current understanding of antimicrobial harms in general. Although not thought of as traditional adverse events, Clostridium difficile infection and development of resistance during therapy are adverse events that occur as a result of antimicrobial exposure and therefore are discussed. In addition, a distillation of our current understanding of β-lactam specific adverse events will be provided. Finally, new methods of administration are being evaluated that may influence peak concentration-related antimicrobial adverse events.

Carbapenems: a potent class of antibiotics

The purpose of this review is to assess the relative strengths and weaknesses of individual members of the carbapenem class of antibiotics. Clinical trials and review articles were identified from a Medline search (1979 - July 2006), in addition to, reference citations from identified publications, abstracts from the Interscience Conferences on Antimicrobial Agents and Chemotherapy and the 12th International Congress on Infectious Disease, and package inserts. Articles in English were reviewed, with emphasis on those containing efficacy or safety data. Carbapenems bind to critical penicillin-binding proteins, disrupting the growth and structural integrity of bacterial cell walls. They provide enhanced anaerobic and Gram-negative coverage as compared with other beta-lactams and their stability against extended-spectrum beta-lactamases (ESBLs) makes them an effective treatment option. The most common adverse effects are infusion-site complications and gastrointestinal distress. Ertapenem has limited efficacy against non-fermenting, Gram-negative bacteria, restricting its use to community-acquired infections. Imipenem is slightly more effective against Gram-positive organisms and meropenem slightly more effective against Gram-negative organisms. However, both have broad-spectrum activity, including non-fermenting, Gram-negative bacteria. Among non-fermenting, Gram-negatives, resistance to imipenem in particular is increasing. Doripenem is in late-stage clinical development and combines the broad-spectrum coverage of imipenem and meropenem, and more potent activity against Pseudomonas aeruginosa. Due to the increasing challenges represented by ESBLs and multi-drug resistant organisms, the carbapenems are assuming a greater role in the treatment of serious infections. Imipenem and meropenem are presently available and have been shown to be effective against nosocomial infections. Doripenem is an investigational carbapenem that has completed Phase III clinical trials and that has the potential to improve on this efficacy and minimize the emergence of resistance to the carbapenem class.

Vancomycin-induced immune thrombocytopenia

BACKGROUND

Vancomycin has only rarely been implicated as a cause of thrombocytopenia, and there is only limited evidence that this complication is caused by immune mechanisms. We conducted a study to determine whether thrombocytopenia is caused by vancomycin-dependent antibodies in patients being treated with vancomycin.

METHODS

We identified and characterized vancomycin-dependent, platelet-reactive antibodies in patients who had been referred for testing during a 5-year period because of a clinical suspicion of vancomycin-induced thrombocytopenia. We obtained clinical information about the patients from their referring physicians.

RESULTS

Drug-dependent, platelet-reactive antibodies of the IgG class, the IgM class, or both were identified in 34 patients, and clinical follow-up information was obtained from 29 of these patients. The mean nadir platelet count in these patients was 13,600 per cubic millimeter, and severe bleeding occurred in 10 patients (34%). Platelet levels returned to baseline in all 26 surviving patients after vancomycin was stopped. In 15 patients, the drug was continued for 1 to 14 days while other possible causes of thrombocytopenia were investigated. Vancomycin-dependent antibodies were not found in 25 patients who had been given vancomycin and in whom thrombocytopenia did not develop.

CONCLUSIONS

Severe bleeding can occur in patients with vancomycin-induced immune thrombocytopenia. The detection of vancomycin-dependent antiplatelet antibodies in patients receiving the antibiotic in whom thrombocytopenia develops, and the absence of antibodies in patients given the drug in whom platelet counts remain stable, indicate that these antibodies are the cause of the thrombocytopenia.

Thiopental-Induced Neutropenia in Two Patients with Severe Head Trauma

Thiopental has been used for decades in the treatment of refractory intracranial hypertension in patients with traumatic and nontraumatic head injuries. Commonly reported adverse effects include hypotension, hypokalemia, respiratory complications, and hepatic dysfunction. Neutropenia has rarely been reported as an adverse effect of thiopental. We witnessed probable thiopental-induced neutropenia in two patients with traumatic brain injuries who developed increased intracranial hypertension that was refractory to standard therapy. Based on a MEDLINE search of published case reports and literature, we propose two mechanisms by which thiopental-related neutropenia might be explained. The first is inhibition of inflammatory mediator nuclear factor-kappa B (NF-kappa B), leading to granulocyte apoptosis. The second mechanism involves inhibition of calcineurin. Although the precise link between these two mechanisms has not been elucidated, calcineurin is known to regulate NF-kappa B activity. Development of neutropenia does not appear to be correlated with time but may correlate with plasma concentrations of thiopental. The optimum management of drug-induced neutropenia is unclear. The decision to discontinue thiopental in patients who develop neutropenia should be made by weighing the risks versus benefits. Broad-spectrum antibiotics may be required in the presence of fever. The role of hematopoietic growth factors such as granulocyte colony-stimulating factor is not yet defined. Given the adverse infectious consequences of neutropenia, it is essential to closely monitor neutrophil counts in patients receiving thiopental.

A randomized, open-label, multicenter comparative study of the efficacy and safety of piperacillin-tazobactam and cefepime for the empirical treatment of febrile neutropenic episodes in patients with hematologic malignancies

BACKGROUND

The empirical treatment of febrile, neutropenic patients with cancer requires antibacterial regimens active against both gram-positive and gram-negative pathogens. This study was performed to demonstrate the noninferiority of monotherapy with piperacillin-tazobactam, compared with cefepime.

METHODS

We conducted a randomized-controlled, open-label, multicenter clinical trial among high-risk patients from 34 university-affiliated tertiary care medical centers in the United States, Canada, and Australia who were undergoing treatment for leukemia or hematopoietic stem cell transplantation and were hospitalized for empirical treatment of febrile neutropenic episodes. Patients received piperacillin-tazobactam (4.5 g every 6 h) or cefepime (2 g every 8 h) intravenously. The primary outcome was success (defined by defervescence without treatment modification) at 72 h of treatment, end of treatment, and test of cure in the modified intent-to-treat analysis. Secondary outcomes included time to defervescence, microbiological efficacy, the additional use of glycopeptide antibiotics, emergence of resistant bacteria, and safety.

RESULTS

For 528 subjects (265 received piperacillin-tazobactam and 263 received cefepime), success rates were 57.7% and 48.3%, respectively (P = .04) at the 72-h time point, 39.6% and 31.6% (P = .06) at end of treatment, and 26.8% and 20.5% (P = .11) at the test-of-cure visit. The analyses demonstrated noninferiority for piperacillin-tazobactam at all time points (P< or = .0001). Treatment with piperacillin-tazobactam was independently associated with treatment success in multivariate analysis (odds ratio, 1.65; 95% confidence interval, 1.04-2.64; P = .035). Both regimens were well tolerated.

CONCLUSIONS

This study demonstrates the noninferiority and safety of piperacillin-tazobactam monotherapy, compared with cefepime, for the empirical treatment of high-risk febrile neutropenic patients with cancer.