Linezolid: effectiveness and safety for approved and off-label indications

In Vitro and In Vivo Studies of Oritavancin and Fosfomycin Synergism against Vancomycin-Resistant Enterococcus faecium

Therapeutic options for infections caused by vancomycin-resistant enterococci are currently suboptimal. Combination regimens where fosfomycin is used alongside existing treatments are emerging given the proven synergistic potential and PK/PD properties. In the studies presented here, we tested five vanA and five vanB clinical isolates of Enterococcus faecium using a combination of oritavancin + fosfomycin both in vitro (checkerboard, time killing) and in vivo (Galleria mellonella). The combination of oritavancin and fosfomycin increased drug susceptibility, showing a synergistic effect in 80% of isolates and an additive effect in the remaining isolates. The combination restored fosfomycin susceptibility in 85% of fosfomycin-resistant isolates. Time killing on four selected isolates demonstrated that the combination of oritavancin and fosfomycin provided a CFU/mL reduction > 2 log10 compared with the most effective drug alone and prevented the bacterial regrowth seen after 8−24 h at sub-inhibitory drug concentrations. In addition, the combination was also tested in a biofilm assay with two isolates, and a strong synergistic effect was observed in one isolate and an additive effect in the other. Finally, we demonstrated in vivo (Galleria mellonella) a higher survival rate of the larvae treated with the combination therapy compared to monotherapy (fosfomycin or oritavancin alone). Our study provides preclinical evidence to support trials combining oritavancin and fosfomycin for VRE BSI in humans, even when biofilm is involved.

Model Based Identification of Linezolid Exposure-toxicity Thresholds in Hospitalized Patients

Evidence supports linezolid therapeutic drug monitoring as the exposure-response relationship has been identified for toxicity among patients receiving linezolid, but the data to establish the upper limit are limited and the published toxicity thresholds range widely. The purpose of this study was to determine the linezolid exposure-toxicity thresholds to improve the safety of linezolid. This is a multicenter retrospective study of adult patients treated with linezolid from 2018 to 2019. The population pharmacokinetic model of linezolid was established based on 270 plasma concentrations in 152 patients, which showed creatinine clearance and white cell count are covariates affecting the clearance of linezolid, and serum albumin is the covariate affecting the volume of distribution. Classification and regression tree analysis was used to determine the linezolid exposure thresholds associated with an increased probability of toxicity. Among 141 patients included for toxicity analysis, the rate of occurring toxicity was significantly higher among patients with an AUC_{0-24, d1} ≥163 mg h/L, AUC_{0-24, d2} ≥207 mg h/L, AUC_{0-24, ss} ≥210 mg h/L, and C_min,d2 ≥6.9 mg/L, C_min,ss ≥6.9 mg/L, while no threshold was discovered for C_{min, d1}. Those exposure thresholds and duration of linezolid treatment were independently associated with linezolid-related toxicity in the logistic regression analyses. In addition, the predictive performance of the AUC_0-24 and C_min thresholds at day 2 and steady state were close. Considering that the AUC estimation is cumbersome, C_min threshold at 48 h and steady state with a value of ≥6.9 mg/L is recommended to improve safety, especially for patients with renal insufficiency and patients with low serum albumin.

Clinical Use and Adverse Drug Reactions of Linezolid: A Retrospective Study in Four Belgian Hospital Centers

In Belgium, linezolid is indicated for pneumonia and skin and soft tissue infections, but is more broadly used, due to its oral bioavailability and activity against multiresistant organisms. This could increase the risk of adverse drug reactions (ADR), notably hematological disorders (anemia, thrombocytopenia), neuropathy, or lactic acidosis. We analyzed linezolid clinical use in relationship with occurrence of ADR in Belgian hospitals and highlighted risk factors associated with the development of thrombocytopenia. A retrospective analysis of electronic medical records and laboratory tests of adult patients treated with linezolid in four Belgian hospitals in 2016 allowed the collection of ADR for 248 linezolid treatments. Only 19.7% of indications were in-label. ADR included 43 thrombocytopenia, 17 anemia, 4 neuropathies, and 4 increases in lactatemia. In a multi-variate analysis, risk factors of thrombocytopenia were a treatment duration > 10 days, a glomerular filtration rate < 60 mL/min, and a Charlson index ≥ 4. Off-label use of linezolid is frequent in Belgium, and ADR more frequent than reported in the summary of product characteristics, but not statistically associated with any indication. This high prevalence of ADR could be related to a high proportion of patients presenting risk factors in our population, highlighting the importance of detecting them prospectively.

Systematic review and meta-analysis of the efficacy and safety of therapy with linezolid containing regimens in the treatment of multidrug-resistant and extensively drug-resistant tuberculosis

BACKGROUND

Linezolid containing regimens have been proposed as potentially valuable alternatives for the treatment of patients with multidrug-resistant tuberculosis (MDR-TB) or extensively drug-resistant TB (XDR-TB).

METHODS

A systematic review and meta-analysis was conducted to assess the efficacy, safety and tolerability of linezolid for drug-resistant TB (DR-TB) treatment. We searched the Cochrane Controlled Trial Registry, PubMed, Embase, Science Citation Index Expanded (SCI) and China National Knowledge Infrastructure (CNKI), database up to May 2014 to identify studies providing data of the use of linezolid for the treatment of DR-TB.

RESULTS

The search yielded 15 studies (367 patients) including one randomized controlled trial (RCT), covering 239 patients who could be evaluated for effectiveness; 83% [95% confidence interval (CI), 75-90%; I(2)=62.8%] had a favorable outcome, defined as either cure or treatment completion. The pooled rate of culture conversion was 89% (95% CI, 83-95%; I(2)=49.6%). Between the group receiving daily linezolid doses of ≤600 or >600 mg, the mortality was considerably lower in patients treated with less than 600 mg/day (P value <0.001). Of 367 patients for whom data on safety was available, peripheral neuropathy (31%, 95% CI, 19-42%; I(2)=81.7%) and anemia (25%, 95% CI, 15-34%; I(2)=76.6%) were the main adverse effects. Patients receiving less than 600 mg/day were more likely to experience nervous system adverse events (P value <0.01).

CONCLUSIONS

The available evidence suggests that linezolid could be considered as a promising option as treatment of MDR/XDR TB. Randomized trials are warranted to define the dose and frequency of administration.

Co-prescribing of linezolid and serotonergic agents in a general hospital setting

BACKGROUND

Co-prescription of linezolid and serotonergic agents (SSRIs, SNRIs, NaSSA, TCAs) can lead to serotonin syndrome, this study seeks to identify prescribing practise of these agents.

METHODS

Study of all general hospital inpatients prescribed intravenous linezolid in a 3-month period, using drug charts and clinical notes.

RESULTS

Co-prescription occurred in 20% with SSRIs most frequently concurrently used. There were no cases of serotonin syndrome. There was no evidence in clinical notes of vigilance for potential interaction.

CONCLUSION

Co-prescription is common; awareness of potentially serious interaction is not evident in current practice.

Meta-analysis of randomized controlled trials of vancomycin for the treatment of patients with gram-positive infections: focus on the study design

OBJECTIVE

To study the effectiveness and safety of vancomycin compared with that of other antibiotics for the treatment of gram-positive infections.

METHODS

Major electronic databases were searched. Data from published randomized controlled trials (January 1, 1950, to September 15, 2011) were pooled using a meta-analytic method.

RESULTS

Fifty-three trials comparing vancomycin with linezolid, daptomycin, quinupristin-dalfopristin, tigecycline, ceftaroline, ceftobiprole, telavancin, teicoplanin, iclaprim, and dalbavancin were included in the meta-analysis. Individual antibiotics were as effective as vancomycin, except for linezolid, which was more effective than vancomycin for the treatment of skin and soft tissue infections (odds ratio [OR], 1.61; 95% confidence interval [CI], 1.07-2.43). Comparators were as effective as vancomycin in the intent-to-treat population (OR, 1.08; 95% CI, 0.98-1.18) but were more effective in the clinically evaluable population (OR, 1.14; 95% CI, 1.02-1.27) when all infections were pooled. When available data from all trials were pooled, no differences were noted when patients with febrile neutropenia (OR, 1.07; 95% CI, 0.82-1.39), pneumonia (OR, 1.10; 95% CI, 0.87-1.37), bacteremia (OR, 1.05; 95% CI, 0.76-1.45), and skin and soft tissue infections (OR, 1.11; 95% CI, 0.89-1.39) were studied. Comparators were more effective in open-label (OR, 1.28; 95% CI, 1.08-1.50) but not in double-blind trials (OR, 1.04; 95% CI, 0.90-1.20). Total adverse events attributed to studied antibiotics (OR, 1.07; 95% CI, 0.90-1.28) and patients withdrawn from trials (OR, 0.86; 95% CI, 0.68-1.09) were similar in the compared groups. Mortality was not different between vancomycin and comparator antibiotics when all trials were included in the analysis (OR, 1.09; 95% CI, 0.96-1.23). Comparators were associated with higher mortality in open-label (OR, 1.27; 95% CI, 1.05-1.54) but not double-blind trials (OR, 0.96; 95% CI, 0.80-1.14).

CONCLUSION

On the basis mainly of data from open-label trials, vancomycin is a treatment choice that is as effective as other available antibiotics for patients with gram-positive infections. Study design seems to make a major contribution to the outcome.

Effectiveness and use of linezolid in hospitalisation wards

OBJECTIVE

To describe the use and effectiveness of linezolid as an alternative treatment for methicillin-resistant Staphylococcus aureus.

METHOD

Demographic, clinical and safety data were collected from hospitalised patients. The information sources were the clinical records and the pharmacy programme.

RESULTS

Thirty patients were treated with linezolid (median age 69.3, 63% male). The median duration of treatment was 8 days. The most prevalent indication was soft tissues and skin infections (46.7%). The indications were off-label in 40% of cases. Linezolid was used as a targeted therapy in 53%, especially for coagulase-negative Staphylococcus. Clinical healing occurred in 83.3%, and microbiological healing in 40%. Three patients (10%) experienced side effects from using linezolid.

CONCLUSION

The effectiveness and safety of linezolid is similar to that described in the trials. Its off-label use and the high number of empirical treatments mean that new strategies must be developed.

Clinical Experience with Linezolid at a Large Academic Medical Center: A Case Series and Review of the Literature

Purpose

The objectives of this study were to evaluate current patterns of use, microbiologic cure rates, and hematologic toxicities, including identification of risk factors, associated with linezolid utilization at our institution.

Methods

Utilization, clinical, microbiological, and toxicity data were collected prospectively over an 8-month period (August 1, 2006 to March 31, 2007). Binary logistic and multivariate stepwise regression analyses were performed to identify potential risk factors for linezolid-associated thrombocytopenia and anemia.

Results

A total of 116 linezolid courses (102 patients) were identified with a mean duration of therapy of 12.3 days. Appropriate infectious disease service approval and consults were found in 87.9% and 62.1% of the cases, respectively. Bloodstream, urinary tract, and respiratory tract infections accounted for 29%, 21%, and 16% of clinical indications, respectively. Vancomycin-resistant enterococci (VRE), methicillin-resistant Staphylococcus aureus (MRSA), and coagulase-negative staphylococci accounted for 43%, 24%, and 7% of clinical isolates, respectively. Overall, the microbiologic cure rate among evaluable patients was 83.8%. Development of thrombocytopenia was found in approximately 30% of linezolid-treated patients. Risk factors for linezolid-associated thrombocytopenia included female gender (OR 5.66, P = .002), serum creatinine (SCr) ≥ 2 mg/dL (OR 4.48, P = .009), intensive care unit admission (OR 3.06, P = .038), and duration of therapy ≥ 28 days (OR 3.76, P = .049).

Conclusion

Utilization patterns may suggest strategies for conserving linezolid, including improved compliance with current approval policies and clinical pathway development. Linezolid microbiological cure rates were similar to those found in the primary literature. Linezolid-associated thrombocytopenia was common and risk factors were identified. Further well-designed prospective studies are needed to confirm these findings. Hosp Pharm-2010;45(12):916-926

Looking toward basic science for potential drug discovery targets against community-associated MRSA

The difficulties to find a conventional vaccine against Staphylococcus aureus and the increasing resistance of S. aureus to many antibiotics demand the exploration of novel therapeutic options, such as by targeting virulence determinants and using specific antibodies in an antitoxin-like approach. Community-associated methicillin-resistant S. aureus (CA-MRSA) strains have recently emerged predominantly in the US, causing epidemic outbreaks of mostly skin and soft tissue infections, but also more dramatic and sometimes fatal diseases. MRSA is now the most frequent cause of death by a single infectious agent in the US. The fact that, at least in the US, CA-MRSA infections are almost entirely due to one sequence type, USA300, gives researchers a novel, unique chance to focus on one clone in their efforts to analyze pathogenesis in a clinically important S. aureus. While the molecular underpinnings of the exceptional virulence and transmissibility of USA300 are not yet well understood, recent findings indicate that increased expression of widespread virulence determinants and acquisition of mobile genetic elements have to be considered. Delineating the relative importance of virulence determinants in USA300 and other important clinical strains is a key endeavor needed to develop a potential antitoxin for CA-MRSA disease.

[Pharmacokinetic evaluation of linezolid in patients with major thermal injuries]

The aims of this multicentre open-label study was to evaluate the pharmacokinetics of linezolid in patients with burn injury above 20 % BSA and to compare them with healthy volunteers, matched in age, sex and weight. After a single 600 mg IV dose of linezolid, multiple blood and urine samples were taken from subjects, in order to determine linezolid concentrations, using a HPLC assay. C(max) and volume of distribution at steady state were not different between the two groups. Values describing clearance were altered in burns, leading to a reduction by half in AUC in these patients (42.5 versus 98.1 mghL(-1)). The enhancement of clearance was due to which of non renal clearance (323+/-191 versus 80.4+/-27.5 mLmin(-1)). We conclude that pharmacokinetics of linezolid are altered in burn patients, in a magnitude sufficient that linezolid concentration may be subtherapeutic in some patients and we suggest that the dosage interval may need to be decreased in this patient population.

Linezolid-induced purpuric medication reaction

A 64-year-old Caucasian male was seen in consultation for a petechial eruption that began 9 days after he started linezolid therapy for a retroperitoneal abscess. Skin findings included confluent non-blanching petechiae and purpura covering his entire body, without any active bleeding. A punch biopsy from the left lateral arm was performed and showed a perivascular inflammatory infiltrate composed of lymphocytes, histiocytes and rare eosinophils, and extravasated erythrocytes. Changes of leukocytoclastic vasculitis were not noted. Linezolid was promptly discontinued. To our knowledge, this is the first report of a biopsy-proven purpuric medication reaction secondary to linezolid therapy.

Linezolid for patients with neutropenia: are bacteriostatic agents appropriate?

A long-held doctrine is that bactericidal antibiotics are required for infections in neutropenic patients. We evaluated the available published evidence regarding the role of linezolid, a bacteriostatic antibiotic, in neutropenic patients with Gram-positive infection. We retrieved two prospective comparative studies (one of them a double-blind, randomized, controlled trial), a prospective cohort study, two retrospective studies and eight case reports that focused on the use of linezolid for Gram-positive bacterial infections in neutropenic patients. Linezolid was administered to 438 neutropenic patients, mainly on a compassionate-use basis, as other antibiotics failed to cure the infection or were associated with significant adverse events. The clinical cure rate ranged between 57 and 87.3% in the intention-to-treat population of the prospective studies. In total, 56 out of 438 (12.7%) neutropenic patients that received linezolid died during therapy. In the only randomized controlled trial that compared linezolid with vancomycin in the treatment of Gram-positive infections in neutropenic patients, mortality was 5.6 versus 7.6%, respectively (p = 0.4). In conclusion, the available evidence suggests that linezolid may be successful in a significant proportion of neutropenic patients with infection, despite the fact that it is a bacteriostatic agent. Such data seem to justify further studies regarding the role of linezolid in this patient population.

Linezolid for the treatment of drug-resistant infections

Multidrug-resistant pathogens have become increasingly common in contemporary healthcare. Specific to Gram-positive pathogens, methicillin-resistant Staphylococcus aureus (MRSA) is of particular concern, as it has been associated with increased hospital length of stay, higher healthcare expenditures and poorer outcomes. To date, linezolid is the first and only oxazolidinone approved by the US FDA for the treatment of infections caused by Gram-positive pathogens, including MRSA. This article will serve as a comprehensive review of linezolid, including an overview of the current market and its in vitro activity, with an in-depth review of its pharmacokinetic and pharmacodynamic profile. Emphasis will be placed on clinical data for the drug, both on- and off-label. The article will conclude with a brief overview of linezolid's pharmacoeconomic implications and safety profile, followed by a commentary and 5-year prospective analysis remarking on the future of the antimicrobial field as it relates to MRSA.

Pharmacokinetic evaluation of linezolid in patients with major thermal injuries

AIMS

To evaluate the pharmacokinetics of linezolid following its administration in patients with major thermal injuries and in a group of healthy volunteers.

METHODS

In an open-label, multicentre design with two parallel groups, a group of patients with major thermal injuries (>20% body area) and a group of age-, sex- and weight-matched healthy volunteers, subjects received a single 600 mg intravenous dose of linezolid. Serial blood and urine collections were made and the concentrations of linezolid in these samples were determined by HPLC. Non-compartmental analyses were used to describe the pharmacokinetic disposition of linezolid.

RESULTS

C(max) concentrations and the volume of distribution at steady state (V(ss)) were not statistically different (P > 0.05) between the two groups of subjects. In contrast, values describing clearance [elimination rate constant (k(el)), t(1/2) and mean residence time (MRT)] were significantly different (P < 0.05) in patients with thermal injuries compared with volunteers, which lead to an approximate reduction by half in AUC(0-infinity) from 98.1 mg.h/L (volunteers) to 42.5 mg.h/L (patients). Although renal clearance was similar in the two groups (24.7 +/- 23 versus 30.6 +/- 14.3 mL/min; P = 0.156), non-renal clearance was substantially increased (323 +/- 191 versus 80.4 +/- 27.5 mL/min) in the patients with thermal injuries, though this difference did not achieve statistical significance (P = 0.063).

CONCLUSIONS

The pharmacokinetics of linezolid are altered in patients with major thermal injuries, mainly as a result of increased non-renal clearance. These changes are of sufficient magnitude that linezolid concentrations may be sub-therapeutic in some patients and we suggest that the dosage interval may need to be decreased in this patient population.

Ceftaroline: a novel broad-spectrum cephalosporin with activity against meticillin-resistant Staphylococcus aureus

Ceftaroline is a broad-spectrum cephalosporin currently under clinical investigation for the treatment of complicated skin and skin-structure infections (cSSSI), including those caused by meticillin-resistant Staphylococcus aureus (MRSA), and community-acquired pneumonia (CAP). Ceftaroline has the ability to bind to penicillin-binding protein (PBP)2a, an MRSA-specific PBP that has low affinity for most other beta-lactam antibacterials. The high binding affinity of ceftaroline to PBP2a (median inhibitory concentration 0.90 microg/mL) correlates well with its low minimum inhibitory concentration for MRSA. Ceftaroline is active in vitro against Gram-positive cocci, including MRSA, meticillin-resistant Staphylococcus epidermidis, penicillin-resistant Streptococcus pneumoniae and vancomycin-resistant Enterococcus faecalis (not E. faecium). The broad-spectrum activity of ceftaroline includes many Gram-negative pathogens but does not extend to extended-spectrum beta-lactamase-producing or AmpC-derepressed Enterobacteriaceae or most nonfermentative Gram-negative bacilli. Ceftaroline demonstrates limited activity against anaerobes such as Bacteroides fragilis and non-fragilis Bacteroides spp. Limited data show that ceftaroline has a low propensity to select for resistant subpopulations. Ceftaroline fosamil (prodrug) is rapidly converted by plasma phosphatases to active ceftaroline. For multiple intravenous doses of 600 mg given over 1 h every 12 hours for 14 days, the maximum plasma concentration was 19.0 microg/mL and 21.0 microg/mL for first and last dose, respectively. Ceftaroline has a volume of distribution of 0.37 L/kg (28.3 L), low protein binding (<20%) and a serum half-life of 2.6 hours. No drug accumulation occurs with multiple doses and elimination occurs primarily through renal excretion (49.6%). Based on Monte Carlo simulations, dosage adjustment is recommended for patients with moderate renal impairment (creatinine clearance 30-50 mL/min); no adjustment is needed for mild renal impairment. Currently, limited clinical trial data are available for ceftaroline. A phase II study randomized 100 patients with cSSSI to intravenous ceftaroline 600 mg every 12 hours or intravenous vancomycin 1 g every 12 hours with or without intravenous aztreonam 1 g every 8 hours (standard therapy) for 7-14 days. Clinical cure rates were 96.7% for ceftaroline compared with 88.9% for standard therapy. Adverse events were similar between groups and generally mild in nature. In a phase III trial, 702 patients with cSSSI were randomized to ceftaroline 600 mg or vancomycin 1 g plus aztreonam 1 g, each administered intravenously every 12 hours for 5-14 days. Ceftaroline was noninferior to vancomycin plus aztreonam in treating cSSSI caused by both Gram-positive and -negative pathogens. Adverse event rates were similar between groups. Ceftaroline is well tolerated, which is consistent with the good safety and tolerability profile of the cephalosporin class. In summary, ceftaroline is a promising treatment for cSSSI and CAP, and has potential to be used as monotherapy for polymicrobial infections because of its broad-spectrum activity. Further clinical studies are needed to determine the efficacy and safety of ceftaroline, and to define its role in patient care.

Pharmacoeconomics of linezolid

BACKGROUND

New antibiotics efficacious in infections caused by resistant Gram-positive microorganisms and with acceptable costs for national health systems per unit of effectiveness are needed.

OBJECTIVE

This paper aimed to summarize all available evidence regarding the pharmacoeconomics of linezolid.

METHODS

A systematic review of pharmacoeconomic analyses through a non-restricted literature search was conducted.

RESULTS/CONCLUSIONS

Linezolid, as compared to vancomycin and teicoplanin, results in a reduction of the necessary resources for the treatment of infections caused by Gram-positive microorganisms. These benefits are attributable to clinical outcomes and to savings associated with the ease of switching from intravenous to oral administration, the shorter duration of intravenous therapy and earlier hospital discharge. Likewise, linezolid, compared to vancomycin and teicoplanin, is a cost-effective treatment.