High accumulation of linezolid and its major metabolite in the serum of patients with hepatic and renal dysfunction is significantly associated with thrombocytopenia and anemia

This study aims to examine the serum levels of linezolid and its metabolites (PNU-142300 and PNU-142586) in patients with varying hepatic and renal function. It seeks to understand how these levels relate to thrombocytopenia and anemia and to identify concentration thresholds that could cause these adverse effects, thereby aiding in personalized drug dosing. This prospective study was conducted from January to December 2023. According to the established inclusion and exclusion criteria, 77 patients with infections treated with linezolid were selected as the research subjects. Venous blood samples were collected every 48 h starting from the first use of linezolid, specifically 30 min before the next dose. Laboratory data were obtained through biochemical analysis and blood routine tests, and blood drug concentration monitoring was carried out based on the pre-established high-performance liquid chromatography (HPLC) method. The exposure levels of linezolid and its metabolites in the serum of patients under different liver and kidney function states were compared, and the relationships between these drug exposure levels and platelet count and hemoglobin concentration were analyzed. Additionally, the receiver operating characteristic (ROC) curve was used to determine the blood drug concentration thresholds of linezolid and its metabolites that led to thrombocytopenia or anemia. Finally, survival analysis was used to evaluate the time differences in the occurrence of adverse reactions, such as thrombocytopenia and anemia, between the liver and kidney function impairment group and the normal group after the use of linezolid. Exposure to linezolid and its metabolites increased with the severity of hepatic and renal impairment. Patients with severe and moderate hepatic and renal impairment had a substantially higher median Cmin of linezolid and its metabolites 2 and 3 than those with mild hepatic and renal impairment. The platelet count and hemoglobin concentration were significantly associated with linezolid and its metabolite overexposure. The concentration threshold for linezolid and its metabolites 2 and 3 to cause thrombocytopenia and anemia were 7.0, 3.6, and 4.3 mg/L. Patients with hepatic and renal impairment exhibit higher levels of linezolid and its metabolites, potentially leading to adverse effects like thrombocytopenia and anemia. It is recommended to monitor drug levels and develop individualized dosage regimens.

IMPORTANCE

The accumulation of plasma linezolid and its metabolites increased with the degree of liver and kidney injury. High plasma linezolid and its metabolite accumulation is significantly associated with thrombocytopenia and anemia. Linezolid and its metabolite concentration threshold can warn the clinical prevention of hematological adverse reactions. Individual therapy guided by therapeutic drug monitoring (TDM) can improve the efficacy of linezolid and reduce toxic reactions. Patients with severe hepatic and renal dysfunction should actively monitor the blood routine and linezolid concentration and adjust the dosage in time.

Common Bacterial Infections in Persons Who Inject Drugs

Opioid use in the United States has increased dramatically. Bacterial infections are common among persons who inject drugs (PWID), and there is a disparity in the care these individuals receive. As such, outcomes associated with these infections can be poor. Healthcare providers can address these disparities through optimal pharmacotherapy recommendations and assistance with changing approaches to the management of PWID.

Clinical research for saliva-based therapeutic drug monitoring of linezolid

AIMS

Linezolid is primarily used to treat of methicillin-resistant Staphylococcus aureus and multidrug-resistant tuberculosis infections. Thrombocytopenia due to linezolid usage is a concern, and therapeutic drug monitoring has been reported to be effective in its prevention. Plasma concentrations provide valuable information for treatment decisions; however, collecting plasma samples can be burdensome for both patients and healthcare providers. Therefore, there is interest in saliva as an alternative for monitoring, considering its potential to replace plasma samples.

METHODS

Patients hospitalized at Hokkaido University Hospital and Hokkaido Spinal Cord Injury Center between April 2022 and July 2024, who received oral or intravenous linezolid treatment, were enrolled. The concentrations of linezolid were simultaneously measured in plasma and saliva samples. We determined the concentration profiles of linezolid in the saliva and examined the correlation between saliva and plasma linezolid concentrations.

RESULTS

Eighteen patients receiving linezolid were enrolled. The average of saliva/plasma (S/P) concentration ratios of linezolid were 1.018. A strong correlation was found between the salivary and plasma concentrations of linezolid (R = .833, P < .001). Notably, in patients receiving intravenous administration of linezolid, the correlation was even more pronounced (R = .885, P < .001). Additionally, when focusing on the S/P ratio of the trough concentrations in the morning and at night, the S/P ratios at night were much closer to 1.0.

CONCLUSION

The concentrations of linezolid in plasma and saliva were similar, indicating their potential applicability in clinical settings. The monitoring of linezolid concentrations in saliva has been shown to be particularly suitable for patients receiving intravenous administration.

Clinical efficacy and safety assessment of tedizolid using therapeutic drug monitoring

Thrombocytopenia derived from tedizolid (TZD) has been reported but less frequently than that from linezolid. Only a few reports have investigated the relationship between the efficacy and safety of TZD administration. This study aimed to measure TZD concentration and investigate the relationship between efficacy and safety. The study was conducted at the Aichi Medical University Hospital. All patients administered TZD were included; the serum trough concentration (Cmin) of TZD was measured using LM1010 high-performance liquid chromatography. Efficacy was assessed as clinical and microbiological efficacy. Clinical efficacy was defined as no recurrence and no need for additional treatment until 2 weeks after the end of TZD therapy. Microbiological efficacy was defined as the absence of bacteria during and after TZD therapy. Safety was assessed using thrombocytopenia. Thrombocytopenia was defined as a decrease in platelet count of ≥25 % compared with baseline levels and a minimum count of <10 × 104/μL. Seventeen patients were included. The Cmin in 16 patients was <0.5 μg/mL; one patient had a Cmin of 1.01 μg/mL complicated by hepatic cirrhosis. Clinical and microbiological efficacy was found in >80 % of the patients. Thrombocytopenia occurred in 14.3 % (2/14) of the patients. The Cmin in two patients with thrombocytopenia were 0.14 and 0.28 μg/mL, respectively. The serum concentration of TZD might increase in patients with hepatic cirrhosis; therapeutic drug monitoring may be required. Thrombocytopenia due to TZD could occur regardless of its serum concentration, necessitating monitoring for platelet count.

Development and validation of a nomogram to predict linezolid-induced thrombocytopenia in hospitalized adults

BACKGROUND

Linezolid (LZD) is used to treat infectious diseases caused by Gram-positive bacteria, but thrombocytopenia is one of the main adverse reactions to LZD administration. Early prediction of linezolid-induced thrombocytopenia (LI-TP) is of great importance to improve the clinical outcomes and prognoses. The aim of this study was to develop and validate a prediction model for LI-TP.

METHODS

A retrospective cohort of hospitalized adults receiving LZD therapy (January 2014-June 2022) was analyzed. Independent risk factors for LI-TP were identified via logistic regression in the training set (n = 757). A nomogram model for LI-TP were developed based on independent risk factors, and verified in validation set (n = 123).

RESULTS

The incidence of LI-TP was 13.5% (102/757). A logistic regression model was developed based on the seven independent risk factors, including age (≥ 60 y), duration of LZD therapy (> 11 d), bPLT (< 308 × 109/L), ALT (> 100 IU/L), Ccr (< 67.5 mL/min), and concomitant use with VPA or Tac (p < 0.01) and transformed into a quantifiable nomogram. The nomogram demonstrated strong discrimination with AUCs of 0.760 in training (95% CI: 0.709-0.812, P < 0.001) and 0.767 in validation (95% CI: 0.635-0.899, P < 0.001). The calibration curves and Hosmer-Lemeshow tests confirmed good reliability and specificity of the nomogram model.

CONCLUSION

This nomogram provides a practical tool for stratifying LI-TP risk, which provide an important reference for enabling timely clinical interventions to enhance LZD safety.

Exploring the impact of baseline platelet count on linezolid-induced thrombocytopenia: a retrospective single-center observation study

BACKGROUND

Patients treated with linezolid (LZD) frequently develop thrombocytopenia, and previous studies have identified the risk factors for this condition. However, the relationship between the development of LZD-induced thrombocytopenia and baseline platelet count has varied according to different reports.

AIM

To explore the relationship between platelet count and the development of LZD-induced thrombocytopenia.

METHOD

Patients who underwent LZD at Hokkaido University Hospital in Japan from September 2008 to March 2023 were included. We collected data on patient characteristics and platelet counts at baseline and during LZD therapy from the electronic medical records. Thrombocytopenia was defined as a decrease in platelet count by 30% or more from baseline, or a platelet level < 100,000/µL.

RESULTS

Two hundred and ninety-five patients who received LZD were included in this study, of whom 34.9% developed thrombocytopenia. In the early days of LZD treatment, the thrombocytopenia group showed a nearly 5% decrease in platelet count, while the non-thrombocytopenia group exhibited an increase of over 5%. Additionally, focusing on early onset thrombocytopenia (within 5 days), a baseline platelet count of < 150,000/µL was identified as a risk factor for early thrombocytopenia. Conversely, it was also observed that 24.7% of patients with a baseline platelet count ≥ 150,000/µL still developed early thrombocytopenia.

CONCLUSION

Our findings suggest that while a baseline platelet count of < 150,000/µL is a risk factor for the early onset of thrombocytopenia, vigilant monitoring of platelet counts by clinical pharmacists in the early stages of LZD treatment is essential, regardless of baseline platelet levels.

Efficacy of Contezolid in the Treatment of Catheter-Related Bloodstream Infections Caused by Methicillin-Resistant Staphylococcus aureus in a Patient with Hepatorenal Syndrome and Acute Kidney Injury: A Case Report

The Hepatorenal Syndrome-Acute Kidney Injury (HRS-AKI) patients infected with methicillin-resistant Staphylococcus aureus (MRSA) urgently require safe and effective treatment options due to their compromised hepatic and renal functions, as well as thrombocytopenia resulting from hypersplenism. In our case, an HRS-AKI patient who underwent continuous renal replacement therapy for fluid overload developed fever with chills. His blood tests indicated elevated C-reactive protein and neutrophils, low platelet count, and bilateral lung infiltrates. Subsequently, his blood culture and catheter culture confirmed a catheter-related MRSA bloodstream infection. To address this complex clinical challenge, a novel oxazolidinone antibiotic, contezolid (800mg orally every 12 hours), was introduced into the patient's anti-infection regimen. Notably, the patient exhibited remarkable improvements and responded favorably to this treatment. During subsequent follow-up, no recurrence of the infection or drug-related adverse events was observed. The successful utilization of contezolid in this case underscores its potential as a novel therapeutic option for treating MRSA infections in patients with HRS-AKI.

PK/PD-Guided Strategies for Appropriate Antibiotic Use in the Era of Antimicrobial Resistance

Antimicrobial resistance (AMR) poses a critical global health threat, necessitating the optimal use of existing antibiotics. Pharmacokinetic/pharmacodynamic (PK/PD) principles provide a scientific framework for optimizing antimicrobial therapy, particularly to respond to evolving resistance patterns. This review examines PK/PD strategies for antimicrobial dosing optimization, focusing on three key aspects. First, we discuss the importance of drug concentration management for enhancing efficacy while preventing toxicity, considering various patient populations, including pediatric and elderly patients with their unique physiological characteristics. Second, we analyze different PK modeling approaches: the classic top-down approach exemplified by population PK analysis, the bottom-up approach represented by physiologically based PK modeling, and hybrid models combining both approaches for enhanced predictive performance. Third, we explore clinical applications, including nomogram-based dosing strategies, Bayesian estimation, and emerging artificial intelligence applications, for real-time dose optimization. Critical challenges in implementing PK/PD simulation are addressed, particularly the selection of appropriate PK models, the optimization of PK/PD indices, and considerations concerning antimicrobial concentrations at infection sites. Understanding these principles and challenges is crucial for optimizing antimicrobial therapy and combating AMR through improved dosing strategies.

Pharmacology of emerging drugs for the treatment of multi-drug resistant tuberculosis

Mycobacterium tuberculosis (TB) remains the leading cause of infection-related mortality worldwide. Drug resistance, need for multiple antimycobacterial agents, prolonged treatment courses, and medication-related side effects are complicating factors to TB cure. The introduction of treatment regimens containing the novel agents bedaquiline, pretomanid, and linezolid, with or without moxifloxacin (BPaL-M or BPaL, respectively) have substantially reduced TB-related morbidity and mortality and are associated with favorable rates of treatment completion and cure. This review summarizes key information on the pharmacology and treatment principles for moxifloxacin, bedaquiline, delamanid, pretomanid, linezolid, and tedizolid in the treatment of multi-drug resistant TB, with recommendations provided to address and attenuate common adverse effects during treatment.

Therapeutic drug monitoring of linezolid and exploring optimal regimens and a toxicity-related nomogram in elderly patients: a multicentre, prospective, non-interventional study

BACKGROUND

The concentrations of linezolid, its optimal regimen and the associated side effects in elderly patients remain unclear.

METHODS

In this multicentre, prospective study, elderly patients receiving linezolid at four tertiary hospitals in Beijing between May 2021 and December 2022 were included. Linezolid concentrations and haematological toxicity were monitored dynamically. Risk factors for linezolid overexposure and moderate-to-severe linezolid-induced thrombocytopenia (M/S LIT) were analysed, and a predictive model of M/S LIT was developed.

RESULTS

A total of 860 linezolid concentrations were measured in 313 patients. The median trough concentrations of linezolid were 24.4 (15.3, 35.8) mg/L at 36-72 h and 26.1 (17.0, 38.1) mg/L at 5-10 days (P = 0.132). Severe linezolid exposure was independently associated with age, estimated glomerular filtration rate (eGFR) and the worst SOFA score (SOFA1), and we further recommended dose regimens for elderly patients based on these findings. The incidences of linezolid-induced thrombocytopenia(LIT) and M/S LIT were 73.5% and 47.6%, respectively. M/S LIT was independently correlated with treatment duration, average trough concentration (TDMa), baseline platelet count, eGFR and baseline SOFA score (SOFA0). The developed nomogram predicted M/S LIT with an area under the curve of 0.767 (95% CI 0.715-0.820), a sensitivity of 71.1% and a specificity of 73.2%.

CONCLUSIONS

Linezolid trough concentrations increased dramatically in the elderly, by about 10 mg/L in patients aged 65-80 years, followed by a further increase of 10 mg/L for every 10 years of age. Therapeutic drug monitoring is recommended in elderly patients receiving linezolid. The developed nomogram may predict M/S LIT and guide dosage adjustments of linezolid. Clinical trial registration number: ChiCTR2100045707.

Therapeutic Drug Monitoring of Linezolid in Drug-Resistant Tuberculosis Patients: Clinical Factors and Hematological Toxicities

Purpose

Previous studies have indicated that the development of severe adverse events is associated with linezolid peak concentration (Cmax), but the factors affecting linezolid Cmax and evidences on therapeutic drug monitoring to anticipate toxicity in drug-resistant tuberculosis (DR-TB) patients have not been clarified clearly. This study aimed to explore the factors influencing linezolid Cmax and investigate the association between linezolid concentration and hematological toxicity.

Patients and Methods

This study included patients with drug-resistant tuberculosis treated with linezolid from January 2022 to September 2023. We analyzed the factors affecting linezolid Cmax using chi-squared and binary logistic regression. The diagnostic utility of linezolid Cmax in predicting hematological toxicity was evaluated using receiver operating characteristic (ROC) analysis.

Results

A total of 76 patients were enrolled in the study. 63.20% met the standard rates for linezolid Cmax. Age (P=0.036), weight (P=0.0016), and creatinine clearance (P=0.0223) significantly correlated with the Cmax. Hematological toxicity was observed in 46.05% (35/76) of patients, characterized by thrombocytopenia (31.58%, 24/76), anemia (6.58%, 5/76), and leukopenia (21.05%, 16/76). ROC curve analysis confirmed the predictive value of linezolid Cmax for thrombocytopenia with an area under curve of 0.728.

Conclusion

Suboptimal linezolid Cmax was prevalent among patients with DR-TB, with age, weight, and renal function emerging as influential factors. Elevated linezolid Cmax increases the risk of thrombocytopenia. Meticulous monitoring of linezolid Cmax is imperative during anti-DR-TB therapy to tailor treatment and mitigate hematological toxicity.

Preclinical toxicity evaluation of novel antibacterial contezolid acefosamil in rats and dogs

Contezolid acefosamil (CZA) is an intravenous prodrug of oxazolidinone antibiotic contezolid (CZD). It is being developed to treat infections due to Gram-positive bacteria including multidrug-resistant pathogens, while addressing myelosuppression and neurotoxicity limitations associated with long-term use of this class of antibiotics. In vivo, CZA is rapidly deacylated into its first metabolite MRX-1352, which is then dephosphorylated to release active drug CZD. Four-week repeat-dose toxicity studies of intravenous CZA were conducted in Sprague-Dawley rats (40, 80, and 160/120 mg/kg/dose twice a day [BID]) and beagle dogs (25, 50, and 100/75 mg/kg/dose BID). The high doses administered to both rats and dogs were adjusted due to adverse effects including decreased body weight and food consumption. Additionally, a dose-dependent transient reduction in erythrocyte levels was recorded at the end of dosing phase. Importantly, no myelosuppressive reduction in platelet counts was observed, in contrast to the myelosuppression documented for standard-of-care oxazolidinone linezolid. The no-observed-adverse-effect level (NOAEL) of CZA was 80 and 25 mg/kg/dose BID in rats and dogs, respectively. Separately, 3-month neuropathological evaluation in Long-Evans rats (25, 37.5, and 50 mg/kg/dose, oral CZA, BID) demonstrated no neurotoxicity in the central, peripheral, and optical neurological systems. Toxicokinetic data from these studies revealed that CZD exposures at NOAELs were higher than or comparable with that for the intended clinical dose. These results confirm the favorable safety profile for CZA and support its clinical evaluation for long-term therapy of persistent Gram-positive infections, beyond the application for earlier oxazolidinones.

Adverse reactions caused by high serum concentration of linezolid: Two case reports and literature review

Linezolid is a potent oxazolidinone for the treatment of various gram-positive bacterial infections. However, the drug can cause potential adverse reactions such as thrombocytopenia, hyperlactacidemia and serotonin syndrome, which warrant consideration by the medical team when planning treatment. The existing literature has reported some adverse reactions caused by linezolid, but most of these are based on clinical characteristics and simple treatment measures. Two cases of linezolid overdose resulting in thrombocytopenia, hyperlactacidemia and serotonin syndrome are presented, which were successfully managed with therapeutic drug monitoring. A dose adjustment strategy was adopted to safely and effectively mitigate linezolid-related adverse events.

Linezolid-Associated Thrombocytopenia: Assessment of Risk Factors in Patients without Hemato-Oncologic Diseases

Background: Linezolid is used for Gram-positive bacterial infections. Thrombocytopenia is one of its main adverse effects resulting from myelosuppression. Several studies have assessed risk factors that may increase the risk of this adverse effect. However, most studies included patients with hemato-oncologic diseases, which may confound such assessments. This study aimed to investigate risk factors for linezolid-associated thrombocytopenia in patients without hemato-oncologic diseases. Methods: This was a multicenter retrospective case-control study of adult patients treated with linezolid twice daily for ≥3 days. Patients with hemato-oncologic diseases, active dengue fever, active COVID-19, baseline platelet count <100 × 103/mm3, concurrent therapy with trimethoprim/sulfamethoxazole or valproic acid, and a recent platelet transfusion within 7 days were excluded. Thrombocytopenia was defined as a drop in platelet count below 100 × 103/mm3. Results: Out of 158 evaluated patients, 33 developed thrombocytopenia, indicating an incidence rate of 20.9%. Of all the risk factors assessed, creatinine clearance of <60 mL/min and bacteremia/infective endocarditis were significantly associated with linezolid-associated thrombocytopenia (adjusted odds ratios, 3.25 and 5.95; 95% CI 1.12-9.45 and 1.23-28.66; p = 0.031 and 0.026, respectively). End of therapy platelet counts were significantly lower in the cases than in the controls (79 vs. 243 × 103/mm3; p < 0.001). Similarly, the percentage of platelet count change was significantly different (-55.1% vs. -10.2%; p < 0.001). Conclusions: In our study, the incidence rate of linezolid-associated thrombocytopenia was 20.9%, and we found that patients with renal impairment and bacteremia may need close monitoring of platelet counts. Prospective studies are warranted to evaluate the potential need for renal dose adjustment.

Comparison of the incidence of nausea and vomiting between linezolid and vancomycin using claims database: a retrospective cohort study

BACKGROUND

Nausea and vomiting during linezolid therapy have been reported as part of safety analyses in clinical trials. We have previously examined the incidence of vomiting during linezolid therapy (18.1%). A previous study conducted at a single hospital showed low external validity. It is necessary to verify whether these results can be reproduced using generalizable data sources.

AIM

To evaluate the incidence of nausea and vomiting during linezolid therapy compared with vancomycin using a Japanese claims database.

METHOD

Patients administered linezolid or vancomycin were selected from the database between January 2005 and June 2017. The primary endpoint was the comparison of nausea and vomiting between the linezolid and vancomycin groups. We conducted propensity score matching (PSM) to adjust for patient characteristics. To assess risk factors for nausea and vomiting, logistic regression was conducted as the secondary endpoint. We defined nausea and vomiting as the first prescription of antiemetics during linezolid or vancomycin therapy as a surrogate endpoint.

RESULTS

In total, 1215 patients were enrolled. After PSM, the number of patients in the linezolid and vancomycin groups was 241. Nausea and vomiting were observed in 11.2% and 5.0% of patients in the linezolid and vancomycin groups, respectively (p < 0.05). Linezolid administration was extracted as a risk factor for nausea and vomiting (odds ratio, 2.09; 95% confidence interval, 1.02-4.30).

CONCLUSION

This study clarified the relationship between linezolid and nausea and vomiting using a Japanese claims database. Further studies are required to elucidate the unknown mechanisms of linezolid-induced nausea and vomiting.

Linezolid-Induced Thrombocytopenia in Patients with Renal Impairment: A Case Series, Review and Dose Advice

BACKGROUND AND OBJECTIVE

Oral linezolid is often used as alternative therapy for intravenous vancomycin. According to the current guidelines, no dose adjustment has to be made in case of renal impairment. Nevertheless, in our hospital we have seen several patients with renal impairment who developed linezolid-induced thrombocytopenia when linezolid was taken in the standard dose. In this case series and review we want to emphasize the necessity of reviewing the Dutch and international guidelines.

METHODS

We describe five cases with renal impairment that developed linezolid-induced thrombocytopenia in our hospital. A PubMed literature review was conducted to identify other cases and find the optimal dosing regimen for these patients.

RESULTS

Our cases join a long list of cases and available literature about linezolid-induced thrombocytopenia in patients with renal impairment. Less linezolid-induced thrombocytopenia was found, both in our cases and in the literature, after dose reduction of 50%. High linezolid trough concentrations were associated with a higher risk of linezolid-induced thrombocytopenia. Besides renal impairment, other risk factors for developing linezolid-induced thrombocytopenia were also identified, such as low body weight, high daily dose/kg, higher age, longer duration of therapy, low baseline count, malignity, low-dose aspirin and interacting co-medication.

CONCLUSION

Re-evaluation of the current dose advice is necessary. We advocate for a standard dose reduction to 50% after 2 days of standard dosing for all patients with an estimated glomerular filtration of <60 mL/min/1.73 m2. Besides this, therapeutic drug monitoring and thrombocytes monitoring may be executed weekly when patients have renal impairment or other risk factors for developing linezolid-induced thrombocytopenia.

Development and validation of a risk prediction model for linezolid-induced thrombocytopenia in elderly patients

OBJECTIVES

Linezolid is the first oxazolidinone antimicrobial agent developed for treating multi-drug-resistant gram-positive bacterial infections. The study aimed to investigate the risk factors of linezolid (LI)-induced thrombocytopenia (LI-TP) and to develop and validate a risk prediction model to identify elderly patients at high risk of developing LI-TP during linezolid therapy.

METHODS

A retrospective cohort study was performed at Zhongshan Hospital, FuDan University, China. The study involved elderly Chinese patients aged ≥65 years administered with linezolid (600 mg) twice a day between January 2015 and April 2021. We collected the patients' clinical characteristics and demographic data from electronic medical records, and compared the differences between LI-TP patients and those who had not developed thrombocytopenia (NO-TP) after linezolid treatment. The risk prediction model was developed based on the regression coefficient generated from logistic regression model.

RESULTS

A total of 343 inpatients were enrolled from January 2015 to August 2020 and were used as the training set. Among them, 67 (19.5%) developed LI-TP. Multivariate logistic regression analysis revealed that baseline platelet counts <150×109·L-1 (odds ratio (OR)=3.576; p<0.001), age ≥75 years (OR=2.258; p=0.009), estimated glomerular filtration rate (eGFR <60 mL·(min·1.73 m2)-1 (OR=2.553; p=0.002), duration of linezolid therapy ≥10 d (OR=3.218; p<0.001), intensive care unit (ICU) admittance (OR=2.682; p=0.004), concomitant piperacillin-tazobactam (OR=3.863; p=0.006) were independent risk factors for LI-TP in elderly patients. The LI-TP risk prediction model was established using a scoring method based on the regression coefficient and exhibited a good discriminative power, with an area under the curve (AUC) of 0.795 (95% confidence interval (CI) 0.740 to 0.851) and 0.849 (95% CI 0.760 to 0.939) in the training set (n=343) and validation set (n=90) respectively.

CONCLUSIONS

These findings indicate that duration of linezolid therapy, age, eGFR, ICU admittance, baseline platelet counts, concomitant piperacillin-tazobactam were significantly associated with LI-TP in elderly patients. A risk prediction model based on these risk factors showed a good discriminative performance and may be useful for clinicians to identify patients at high risk of developing LI-TP.

Prediction of risk factors for linezolid-induced thrombocytopenia based on neural network model

Background: Based on real-world medical data, the artificial neural network model was used to predict the risk factors of linezolid-induced thrombocytopenia to provide a reference for better clinical use of this drug and achieve the timely prevention of adverse reactions. Methods: The artificial neural network algorithm was used to construct the prediction model of the risk factors of linezolid-induced thrombocytopenia and further evaluate the effectiveness of the artificial neural network model compared with the traditional Logistic regression model. Results: A total of 1,837 patients receiving linezolid treatment in a hospital in Xi 'an, Shaanxi Province from 1 January 2011 to 1 January 2021 were recruited. According to the exclusion criteria, 1,273 cases that did not meet the requirements of the study were excluded. A total of 564 valid cases were included in the study, with 89 (15.78%) having thrombocytopenia. The prediction accuracy of the artificial neural network model was 96.32%, and the AUROC was 0.944, which was significantly higher than that of the Logistic regression model, which was 86.14%, and the AUROC was 0.796. In the artificial neural network model, urea, platelet baseline value and serum albumin were among the top three important risk factors. Conclusion: The predictive performance of the artificial neural network model is better than that of the traditional Logistic regression model, and it can well predict the risk factors of linezolid-induced thrombocytopenia.

Derivation and Clinical Utility of Safety Targets for Linezolid-Related Adverse Events in Drug-Resistant Tuberculosis Treatment

Long-term usage of linezolid can result in adverse events such as peripheral neuropathy, anemia and thrombocytopenia. Therapeutic drug monitoring data from 75 drug-resistant tuberculosis patients treated with linezolid were analyzed using a time-to-event (TTE) approach for peripheral neuropathy and anemia and indirect response modelling for thrombocytopenia. Different time-varying linezolid pharmacokinetic exposure indices (AUC0-24h,ss, Cav, Cmax and Cmin) and patient characteristics were investigated as risk factors. A treatment duration shorter than 3 months was considered dropout and was modelled using a TTE approach. An exposure-response relationship between linezolid Cmin and both peripheral neuropathy and anemia was found. The exposure index which best described the development of thrombocytopenia was AUC0-24h. The final TTE dropout model indicated an association between linezolid Cmin and dropout. New safety targets for each adverse event were proposed which can be used for individualized linezolid dosing. According to the model predictions at 6 months of treatment, a Cmin of 0.11 mg/L and 1.4 mg/L should not be exceeded to keep the cumulative probability to develop anemia and peripheral neuropathy below 20%. The AUC0-24h should be below 111 h·mg/L or 270 h·mg/L to prevent thrombocytopenia and severe thrombocytopenia, respectively. A clinical utility assessment showed that the currently recommended dose of 600 mg once daily is safer compared to a 300 mg BID dosing strategy considering all four safety endpoints.

Therapeutic drug monitoring of linezolid: HPLC-based assays for routine quantification of linezolid in human serum and cerebrospinal fluid

OBJECTIVE

Therapeutic drug monitoring (TDM) of linezolid can prevent over- and under-dosing in critically ill patients and can be crucial to successful antibiotic treatment. Quick and simple high-performance liquid chromatography (HPLC) assays for the detection of linezolid in human serum and cerebrospinal fluid (CSF) were developed in this study.

METHODS

The methods used an Atlantis T3 5.0 µm stationary phase. The mobile phase A contained water (99.4% m/m) and formic acid (0.6% m/m) (pH 2.30). The mobile phase B contained acetonitrile (93.6% m/m), water (6% m/m) and formic acid (0.4% m/m). The methods were isocratic, using 23% of mobile phase B and 77% of mobile phase A. Ultraviolet absorbance detection at 252 nm was used. For sample preparation an internal standard was added, and acetonitrile/methanol was added for protein precipitation.

RESULTS

The methods were investigated for linearity, specificity, accuracy, and precision. Stability of linezolid and internal standard was assessed. The retention times of linezolid were 8.5 min and 8.1 min, and the single run time was 15 min. Linezolid was quantified from the lower limit of quantification (0.2 mg/L) to the upper limit of quantification (50 mg/L, 75 mg/L, and 100 mg/L). In routine analysis a high variability of serum and CSF levels was observed and the mean CSF/serum ratio was 0.71±0.16.

CONCLUSION

The developed assays enable the study of correlations between the applied dosage, serum concentration and CSF concentration. Additionally, studies with a higher number of samples can be performed to investigate the penetration of linezolid into the central nervous system.

Risk factors for thrombocytopenia in patients receiving linezolid therapy: a systematic review and meta-analysis

PURPOSE

The incidence of linezolid-induced thrombocytopenia (LIT) has been reported to vary widely across studies. We performed a meta-analysis to identify the risk factors for thrombocytopenia among patients who received linezolid treatment.

METHODS

The PubMed, Embase and Cochrane Library databases were searched from inception to November 2022 to identify eligible studies. Data on the potential predictors of incidence in LIT were pooled using a random effects model. Sensitivity analyses were performed to determine the robustness of the results when significant heterogeneity was observed.

RESULTS

Forty observational studies involving 6454 patients treated with linezolid were included in the analysis. LIT was estimated to occur in 37% of patients. The following important factors were associated with the incidence of LIT: advanced age, body mass index, concurrent renal impairment or liver disease, abnormal laboratory parameters (including white blood cell count, serum creatinine, baseline platelet count, albumin, creatinine clearance rate, and estimated glomerular filtration rate), treatment duration and renal replacement therapy.

CONCLUSIONS

A variety of risk factors related to the occurrence of LIT were revealed in our analysis. Early identification of these factors could help patients improve clinical outcomes.

Effect of Platelet Parameters on Linezolid-Related Thrombocytopenia in Hospitalized Patients

Background

Linezolid-induced thrombocytopenia incidence varies considerably. Linezolid-related thrombocytopenia in patients has received few studies which have investigated risk factors including platelet parameters except for platelet counts. The study aims to analyze the effect of platelet parameters, including mean platelet volume and platelet large cell ratio, on linezolid-related thrombocytopenia in patients.

Methods

The effect of platelet parameters on linezolid-related thrombocytopenia was identified by univariate and multivariate logistic regressions. A Kaplan-Meier survival analysis was carried out to compare the survival of patients who developed linezolid-related thrombocytopenia with patients who did not.

Results

Thrombocytopenia occurred at a rate of 41.5% (66/159) after linezolid therapy in hospitalized patients. Platelet parameters, including the difference in mean platelet volume (MPV/fL=0.08 (-1.2-0.9)vs-0.5 (-1.5-0.3), (OR, 0.459; P = 0.001), the difference in platelet large cell ratio (PLCR/fL=0.9 (-5.1-6.2)vs-3.8 (-8.6-2.4), (OR, 1.156; P = 0.001), baseline platelet counts (OR, 0.995; P = 0.006) and duration of linezolid therapy≥10d (OR, 1.346; P = 0.007), were significantly associated with linezolid-related thrombocytopenia in hospitalized patients. In addition, other risk factors which also are associated with linezolid-related thrombocytopenia include baseline red blood cells, co-medication with parecoxib and co-medication with caspofungin. Accumulated in-hospital mortality of patients with thrombocytopenia was significantly higher than that of patients without thrombocytopenia during linezolid treatment (19.7% vs 8.6%, P = 0.003).

Conclusion

The difference in mean platelet volume, the difference in large platelet ratio, baseline platelet counts and duration of linezolid therapy≥10d significantly affected the development of linezolid-related thrombocytopenia in hospitalized patients.

Nomogram prediction model called "ADPLCP" for predicting linezolid-associated thrombocytopenia in elderly individuals

Background

Linezolid-associated thrombocytopenia (LAT) leads to drug withdrawal associated with a poor prognosis. Some risk factors for LAT have been identified; however, the sample size of previous studies was small, data from elderly individuals are limited, and a simple risk score scale was not established to predict LAT at an early stage, making it difficult to identify and intervene in LAT at an early stage.

Methods

In this single-center retrospective case-control study, we enrolled elderly patients treated with linezolid in the intensive care unit from January 2015 to December 2020. All the data of enrolled patients, including demographic information and laboratory findings at baseline, were collected. We analyzed the incidence and risk factors for LAT and established a nomogram risk prediction model for LAT in the elderly population.

Results

A total of 428 elderly patients were enrolled, and the incidence of LAT was 35.5% (152/428). Age ≥80 years old (OR=1.980; 95% CI: 1.179-3.325; P=0.010), duration of linezolid ≥ 10 days (OR=1.100; 95% CI: 1.050-1.152; P <0.0001), platelet count at baseline (100-149×109/L vs. ≥200×109/L, OR=8.205, 95% CI: 4.419-15.232, P <0.0001; 150-199 ×109/L vs. ≥200×109/L, OR=3.067, 95% CI: 1.676-5.612, P <0.001), leukocyte count at baseline ≥16×109/L (OR=2.580; 95% CI: 1.523-4.373; P <0.0001), creatinine clearance <50 mL/min (OR=2.323; 95% CI: 1.388-3.890; P=0.001), and total protein <60 g/L (OR=1.741; 95% CI: 1.039-2.919; P=0.035) were associated with LAT. The nomogram prediction model called "ADPLCP" (age, duration, platelet, leukocyte, creatinine clearance, protein) was established based on logistic regression. The area under the curve (AUC) of ADPLCP was 0.802 (95% CI: 0.748-0.856; P <0.0001), with 78.9% sensitivity and 69.2% specificity (cut-off was 108). Risk stratification for LAT was performed based on "ADPLCP." Total points of <100 were defined as low risk, and the possibility of LAT was <32.0%. Total points of 100-150 were defined as medium risk, and the possibility of LAT was 32.0-67.5%. A total point >150 was defined as high risk, and the probability of LAT was >67.5%.

Conclusions

We created the ADPLCP risk score scale to predict the occurrence of LAT in elderly individuals. ADPLCP is simple and feasible and is helpful for the early determination of LAT to guide drug withdrawal or early intervention.

Effect of linezolid on platelet count in critically ill patients with thrombocytopenia

INTRODUCTION

Linezolid (LZD) is one of the antibiotics used to treat methicillin-resistant Staphylococcus aureus. In Japan, the dose of LZD is not generally adjusted by renal function or therapeutic drug monitoring and is readily available for critically ill patients. The adverse effects of LZD include pancytopenia, especially thrombocytopenia. We investigated the effect of LZD on platelet counts in critically ill patients with thrombocytopenia during admission to the intensive care unit (ICU).

METHODS

Fifty-five critically ill patients with existing thrombocytopenia (platelet count < 100 ×103 /μL) who received LZD for five days or more during the period from January 2011 to October 2018 were included. Changes in platelet count and frequency of platelet concentrate (PC) transfusion were evaluated retrospectively.

RESULTS

Mean (± standard error) platelet count prior to initiation of LZD was 47 ± 4 ×103 /uL, which increased significantly to 86 ± 13 ×103 /uL on day 15 (p<0.01). Median [interquartile range] duration of LZD therapy was 9 [8-12] days. Thirty-two patients (58.2%) required PC transfusion in the 15-day study period. The daily rate of PC transfusion decreased from 30.2% on days 1-5 to 18.2% on days 11-15. Similar tendencies were observed in patients with non-hematological and hematological disease.

CONCLUSION

Thrombocytopenia in critically ill patients in the ICU did not worsen after initiation of LZD therapy, and may be considered for the treatment of MRSA in this setting.

Monitoring Salivary Concentrations of Tedizolid and Linezolid Using Rats

BACKGROUND AND OBJECTIVE

Therapeutic drug monitoring (TDM) is an effective tool for the management of patients who are administered linezolid. The use of saliva for TDM has potential advantages over the use of plasma; however, only a few reports have compared drug concentrations in the saliva and plasma. Moreover, there are no reports on the salivary concentration of tedizolid, an oxazolidinone antibiotic similar to linezolid. In the present study, the concentrations of tedizolid and linezolid in rat submandibular saliva were compared with those measured in the plasma.

METHODS

Tedizolid (10 mg/kg, n = 6) and linezolid (12 mg/kg, n = 5) were administered via the rat tail vein. Submandibular saliva and plasma samples were collected for up to 8 h after the initiation of drug administration, and assayed for the concentrations of tedizolid and linezolid.

RESULTS

A strong correlation was found between the saliva and plasma concentrations of tedizolid (r = 0.964, p < 0.001) and linezolid (r = 0.936, p < 0.001). The value of tedizolid maximum concentration of drug (C_max) was 0.99 ± 0.08 µg/mL in the saliva and 14.46 ± 1.71 µg/mL in the plasma. Meanwhile, the C_max of linezolid was 8.01 ± 1.42 µg/mL in the saliva and 13.00 ± 1.90 µg/mL in the plasma. According to these results, the saliva/plasma concentration ratios of tedizolid and linezolid in rats were 0.0513 ± 0.0080 and 0.6341 ± 0.0339, respectively.

CONCLUSIONS

Considering the correlation between saliva and plasma concentrations of tedizolid and linezolid, as well as the characteristics of saliva, the results of this study suggest that saliva is a useful matrix for TDM.

Therapeutics for Vancomycin-Resistant Enterococcal Bloodstream Infections

Vancomycin-resistant enterococci (VRE) are common causes of bloodstream infections (BSIs) with high morbidity and mortality rates. They are pathogens of global concern with a limited treatment pipeline. Significant challenges exist in the management of VRE BSI, including drug dosing, the emergence of resistance, and the optimal treatment for persistent bacteremia and infective endocarditis. Therapeutic drug monitoring (TDM) for antimicrobial therapy is evolving for VRE-active agents; however, there are significant gaps in the literature for predicting antimicrobial efficacy for VRE BSIs. To date, TDM has the greatest evidence for predicting drug toxicity for the three main VRE-active antimicrobial agents daptomycin, linezolid, and teicoplanin. This article presents an overview of the treatment options for VRE BSIs, the role of antimicrobial dose optimization through TDM in supporting clinical infection management, and challenges and perspectives for the future.

Bayesian prediction-based individualized dosing of anti-methicillin-resistant Staphylococcus aureus treatment: Recent advancements and prospects in therapeutic drug monitoring

As one of the efficient techniques for TDM, the population pharmacokinetic (popPK) model approach for dose individualization has been developed due to the rapidly growing innovative progress in computer technology and has recently been considered as a part of model-informed precision dosing (MIPD). Initial dose individualization and measurement followed by maximum a posteriori (MAP)-Bayesian prediction using a popPK model are the most classical and widely used approach among a class of MIPD strategies. MAP-Bayesian prediction offers the possibility of dose optimization based on measurement even before reaching a pharmacokinetically steady state, such as in an emergency, especially for infectious diseases requiring urgent antimicrobial treatment. As the pharmacokinetic processes in critically ill patients are affected and highly variable due to pathophysiological disturbances, the advantages offered by the popPK model approach make it highly recommended and required for effective and appropriate antimicrobial treatment. In this review, we focus on novel insights and beneficial aspects of the popPK model approach, especially in the treatment of infectious diseases with anti-methicillin-resistant Staphylococcus aureus agents represented by vancomycin, and discuss the recent advancements and prospects in TDM practice.

Use of Japanese big data from electronic medical records to investigate risk factors and identify their high-risk combinations for linezolid-induced thrombocytopenia

PURPOSE

Thrombocytopenia is a major event associated with linezolid (LZD) therapy. Factors affecting LZD-induced thrombocytopenia (LIT) have been reported in previous studies. However, several issues pertaining to LIT have not yet been clarified. In the present study, we used Japanese big data to investigate associated factors and their high-risk combinations that influence LIT.

METHODS

Patients administered LZD between May 2006 and October 2020 were included in this study. LIT was defined as either a 30% or more reduction from the baseline platelets or platelet values of < 100,000/µL. We evaluated factors affecting LIT and combinations of factors that alter LIT risk according to a decision tree (DT) analysis, a typical machine learning method.

RESULTS

We successfully enrolled 1399 patients and LIT occurred in 44.7% of the patients (n = 626). We classified the laboratory data on renal function, LZD duration, age, and body weight (BW) into smaller categories. The results of multivariate analysis showed that prolonged LZD therapy, BW < 45 kg, estimated glomerular filtration rate (eGFR) < 30 mL/min/1.73 m², and dialysis were risk factors for LIT. The DT analysis revealed that the highest risk was a combination of LZD duration ≥ 14 days and eGFR < 30 mL/min/1.73 m².

CONCLUSIONS

The present study extracted four risk factors and identified high-risk combinations for LIT. Patients with these risk factors should be closely monitored.

Hematological toxicities associated with linezolid therapy in adults: key findings and clinical considerations

INTRODUCTION

Linezolid can cause serious adverse effects including thrombocytopenia and anemia. Here, we focus specifically on linezolid-related hematological toxicity in adult patients requiring prolonged drug treatment.

AREAS COVERED

We review the available evidence on the likelihood of hematological toxicity in adult patients treated with linezolid, with a focus on the main risk factors and strategies to prevent this adverse event. A MEDLINE PubMed search for articles published from January 2000 to May 2022 was completed matching the terms linezolid, hematology, hematological toxicity, anemia, and thrombocytopenia. Moreover, additional studies were identified from the reference lists of retrieved articles.

EXPERT OPINION

Thrombocytopenia is the major concern with administration of linezolid for Gram-positive infections, whereas anemia is more common in patients with tuberculosis. The important clinical risk factors for the development of linezolid-related thrombocytopenia are aging, renal dysfunction, low baseline platelet count, duration of treatment, and linezolid plasma trough concentrations >8 mg/L. Patients receiving linezolid for extended periods of time or patient populations with increased risk of altered drug pharmacokinetics would benefit from therapeutic drug monitoring or from the availability of toxico-dynamic predictive models to optimize linezolid dosing.

A Retrospective Study to Compare the Incidence of Hyponatremia after Administration between Linezolid and Tedizolid

Linezolid (LZD) and Tedizolid (TZD) are oxazolidinone antibiotic for meticillin-resistant Staphylococcus aureus (MRSA). Severe hyponatremia after LZD administration have been reported. Severe hyponatremia cause seizures, unconsciousness, and even death. Therefore, we conducted a study to assess the change of serum sodium level after LZD and TZD therapy. We enrolled 67 patients treated with LZD and 28 treated with TZD. We monitored the serum sodium level from the administration to 14 days after administration of oxazolidinone drug. Hyponatremia was defined a sodiuln level ≤134 mmol/L after the initiation of oxazolidinone drug. The frequency of hyponatremia in the LZD group was significantly higher than that in the TZD group (39.7% vs. 11.1%, p < 0.05). The rate of patients administered by injection was significantly higher than in the LZD group than in the TZD group (52.9% vs. 14.8%, p < 0.01). Multiple logistic regression analyses identified the albumin level before the oxazolidinone drug therapy as the independent variables associated with the development of hyponatremia. We revealed that TZD is safer than LZD in terms of hyponatremia. Therefore, cases that LZD is administered by injection should be used more carefully with hyponatremia in patients with low albumin level.

A standard dose of linezolid puts patients with hepatic impairment at risk of overexposure

PURPOSE

The purpose of this retrospective observational study conducted in patients with hepatic impairment was to assess the variability of linezolid trough concentrations, to determine the risk factors for linezolid overexposure, and to investigate the effect of linezolid overexposure on linezolid-induced thrombocytopenia.

METHODS

All enrolled patients received a standard dose (600 mg every 12 h) of linezolid and underwent therapeutic drug monitoring. The Child-Pugh-Turcotte score was used to divide patients into three groups: mild, moderate, and severe hepatic impairment. The risk factors for linezolid overexposure (C_min > 8 mg/L) and linezolid-induced thrombocytopenia were examined using logistic regression. And the Kaplan-Meier curve was used to describe the association between linezolid overexposure and linezolid-induced thrombocytopenia.

RESULTS

Seventy-seven patients were included, 37 (48.1%) of whom experienced linezolid overexposure. Patients with severe hepatic impairment had a substantially higher median C_min of linezolid than those with mild (20.7 mg/L vs 5.51 mg/L, P < 0.001) or moderate (20.7 mg/L vs 6.70 mg/L, P = 0.001) hepatic impairment. Severe hepatic impairment was significantly associated with linezolid overexposure (OR 7.037, 95%CI 1.426-34.727, P = 0.017). After linezolid treatment, linezolid-induced thrombocytopenia occurred in 32 (41.6%) patients, and C_min > 8 mg/L was a significant predictor of linezolid-induced thrombocytopenia (OR 3.024, 95%CI 1.083-8.541, P = 0.035).

CONCLUSION

Patients with hepatic impairment who received standard doses of linezolid are at greater risk of linezolid overexposure, which may lead to a higher incidence of linezolid-induced thrombocytopenia.

Safety Profile of Linezolid in Older Adults With Renal Impairment: A Population-Based Retrospective Cohort Study

Background

The objective of this study was to characterize the safety profile of linezolid in patients with renal impairment compared with patients without renal impairment.

Methods

A population-based retrospective cohort study using linked administrative databases included patients aged 66 years or older in Ontario, Canadawho were prescribed linezolid from 2014 to 2021. Renal impairment was defined using baseline estimated glomerular filtration rate <30 mL/min/1.73 m² or receipt of dialysis. The primary outcomes were change in platelet count and severe thrombocytopenia (platelet count <50 × 10⁹/L) within 90 days. Secondary outcomes included bleeding, neutropenia, peripheral neuropathy, optic neuropathy, acidosis, serotonin syndrome, and mortality. Inverse probability of treatment weighting on propensity score was used to balance comparison groups on baseline health.

Results

Of 625 patients, 98 (15.7%) patients had renal impairment. The mean (SD) platelet change was -88.3 (108.4) 10⁹/L in the renal impairment group and -76.5 (109.8) 10⁹/L in the no renal impairment group, with an adjusted mean difference of -29.4 (95% CI, -53.4 to -5.3; P = .0165). Severe thrombocytopenia occurred in 9.2% for the renal impairment group and 5.9% for the no renal impairment group, with an adjusted risk difference of 2.7% (95% CI, -3.1% to 8.6%; P = .3655). There were no significant differences in secondary outcomes between the 2 groups.

Conclusions

Patients with renal impairment on linezolid therapy had a larger decrease in platelet count, but their risks for severe thrombocytopenia and bleeding were not significantly different than patients without renal impairment. Linezolid is likely safe in renal impairment without dose adjustment or drug level monitoring.

Pharmacokinetic and pharmacodynamic simulation for the quantitative risk assessment of linezolid-associated thrombocytopenia

WHAT IS KNOWN AND OBJECTIVE

Linezolid (LZD) may cause thrombocytopenia, which can result in discontinuation of treatment. In this study, the blood LZD trough concentration was estimated based on population pharmacokinetic (PK) parameters derived from two previously published models in the Japanese population to determine the rate of achieving the target trough value when the risk of thrombocytopenia is low and to clarify its relationship with the onset of thrombocytopenia.

METHODS

This study included adult patients hospitalized at Shimane University Hospital, who received LZD treatment for at least 4 days from January 2010 to December 2017. Patients whose platelet count fell below 70% before LZD administration were categorized as the thrombocytopenic group. Patient PK parameters were calculated based on the population PK models described by Matsumoto et al. and Sasaki et al., and these parameters were designated A and B, respectively. Based on these parameters, the rate of achieving an LZD trough concentration of less than 8 μg/ml, which is the safety target achievement rate, was calculated using a random simulation for each patient. We further analysed the association between the incidence of thrombocytopenia and patient factors, including safety target achievement rate, through univariate, multivariate, and receiver operating characteristic (ROC) analyses.

RESULTS AND DISCUSSION

Patients (n = 77) aged 72 ± 11 years and weighing 56.7 ± 10.9 kg, with a creatinine clearance (CL_cr ) of 60.5 ± 47.2 ml/min and a cirrhosis prevalence of 9.1%, were analysed. All patients received LZD at a dose of 600 mg twice daily for a total of 10.9 ± 8.9 days. Univariate analyses revealed significant differences (p < 0.05) in the duration of LZD therapy, serum creatinine, creatinine clearance, LZD clearance, and the safety target achievement rate for parameters A and B between the thrombocytopenic and non-thrombocytopenic groups. A multivariate analysis of these factors stratified with the cutoff values obtained by ROC analysis revealed that the duration of LZD therapy and the safety target achievement rates for parameters A and B were significant factors (odds ratios for duration of LZD therapy: 7.436 [95% confidence interval (CI): 1.918-28.831] and 4.712 [95% CI: 1.567-14.163]; odds ratio for safety target achievement rate: 0.060 [95% CI: 0.016-0.232] and 0.167 [95% CI: 0.056-0.498] for parameters A and B, respectively). When the safety target achievement rates for patients treated with LZD were compared between the thrombocytopenic and non-thrombocytopenic groups, the safety target achievement rate was higher in the non-thrombocytopenic group in both the patients treated with LZD for less than 10 days and those for 10 days or more. Therefore, the safety target achievement rate estimated by the PK/PD simulation may represent to be an important index for risk assessment of LZD-induced thrombocytopenia.

WHAT IS NEW AND CONCLUSION

The risk of LZD-induced thrombocytopenia, which increased with the duration of LZD therapy, may be predicted using the safety target achievement rate obtained by the blood concentration simulation.

Safety of linezolid in patients with decreased renal function and trough monitoring: a systematic review and meta-analysis

BACKGROUND

Linezolid causes hematological toxicity, mostly thrombocytopenia, which leads to treatment discontinuation and failure. Recent studies revealed that during linezolid therapy, the incidence of treatment-related hematological toxicity is significantly higher in patients with decreased renal function (DRF) than in those with normal renal function. Linezolid monitoring is necessary due to the high frequency of hematological toxicity in patients with DRF and the relationship between blood concentration and safety. We performed a systematic review and meta-analysis to evaluate the safety correlation between DRF and trough monitoring.

METHODS

Articles published before June 24, 2022, on MEDLINE, Web of Sciences, Cochrane Register of Controlled Trials, and ClinicalTrials.gov were systematically analyzed. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using the Mantel-Haenszel method and the variable effects model.

RESULTS

The incidence of hematological toxicity was significantly higher in patients with DRF than in those without DRF (OR = 2.37; p < 0.001). Subgroup analysis, performed according to hematotoxicity classification, including thrombocytopenia, anemia, and pancytopenia, revealed a significantly higher incidence of thrombocytopenia (OR = 2.45; p < 0.001) and anemia (OR = 2.31; p = 0.006) in patients with DRF than in those without; pancytopenia (OR = 1.41; p = 0.80) incidences were not significantly higher. Based on a systematic review, linezolid trough concentrations > 6-7 μg/mL may be associated with an increased incidence of thrombocytopenia. However, no confidential threshold values for the development of thrombocytopenia were found in the area under the concentration curve values for children or adults.

CONCLUSION

We observed a high frequency of hematological toxicity during linezolid therapy in patients with DRF. To ensure safety, linezolid trough concentrations should be ≤6-7 μg/mL.

Successful treatment of disseminated nocardiosis diagnosed by metagenomic next-generation sequencing: A case report and review of literature

BACKGROUND

Nocardia paucivorans is an infrequently found bacterium with the potential to cause severe infection, with a predilection for the central nervous system, both in immunocompromised and immunocompetent individuals. Rapid etiological diagnosis of nocardiosis can facilitate timely and rational antimicrobial treatment. Metagenomic next-generation sequencing (mNGS) can improve the rate and reduce the turnaround time for the detection of Nocardia.

CASE SUMMARY

A 49-year-old man was admitted to hospital with cough and hemoptysis. Imaging revealed pulmonary consolidation as well as multiple brain lesions. Nocardia asiatica and Nocardia beijingensis were rapidly detected by mNGS of bronchoalveolar lavage fluid (BALF) while bacterial culture of BALF and pathological biopsy of lung tissue were negative. In early stages, he was treated with trimethoprim-sulfamethoxazole (TMP-SMZ) and linezolid by individual dose adjustment based on serum concentrations and the adverse effects of thrombocytopenia and leukopenia. The treatment was then replaced by TMP-SMZ and ceftriaxone or minocycline. He was treated with 8 mo of parenteral and/or oral antibiotics, and obvious clinical improvement was achieved with resolution of pulmonary and brain lesions on repeat imaging.

CONCLUSION

mNGS provided fast and precise pathogen detection of Nocardia. In disseminated nocardiosis, linezolid is an important alternative that can give a better outcome with the monitoring of linezolid serum concentrations and platelet count.

Relationship Between Linezolid Exposure and the Typical Clinical Laboratory Safety and Bacterial Clearance in Chinese Pediatric Patients

Objectives: There have been limited studies concerning the safety and efficacy of linezolid (LZD) in children. This study aimed to evaluate the association between LZD exposure and clinical safety and efficacy in Chinese pediatric patients.

Methods: This retrospective cross-sectional study included patients ≤18 years of age who received ≥3 days of LZD treatment between 31 January 2015, and 31 December 2020. Demographic characteristics, medication information, laboratory test information, and bacterial culture results were collected from the Hospital Information System (HIS). Exposure was defined as AUC₂₄ and calculated by the non-linear mixed-effects modeling program (NONMEM), version 7.2, based on two validated population pharmacokinetic models. Binary logistic regression analyses were performed to analyze the associations between AUC₂₄ and laboratory adverse events, and receiver operating characteristic curves were used to calculate the cut-off values. Efficacy was evaluated by bacterial clearance.

Results: A total of 413 paediatric patients were included, with an LZD median (interquartile range) dose, duration, clearance and AUC₂₄ of 30.0 (28.1-31.6) mg/kg/day, 8 (4‒15) days,1.31 (1.29-1.32) L/h and 81.1 (60.6-108.7) mg/L·h, respectively. Adverse events associated with TBil, AST, ALT, PLT, hemoglobin, WBC, and neutrophil count increased during and after LZD treatment when compared with before medication (p < 0.05), and the most common adverse events were thrombocytopaenia (71/399, 17.8%) and low hemoglobin (61/401, 15.2%) during the LZD treatment. Patients with AUC₂₄ higher than 120.69 mg/L h might be associated with low hemoglobin 1–7 days after the end of the LZD treatment, and those with an AUC₂₄ higher than 92.88 mg/L∙h might be associated with thrombocytopaenia 8–15 days after the end of the LZD treatment. A total of 136 patients underwent bacterial culture both before and after LZD treatment, and the infection was cleared in 92.6% (126/136) of the patients, of whom 69.8% (88/126) had AUC₂₄/MIC values greater than 80.

Conclusion: Hematological indicators should be carefully monitored during LZD treatment, especially thrombocytopaenia and low hemoglobin, and a continuous period of monitoring after LZD withdrawal is also necessary. Since the AUC₂₄ cut-off values for laboratory adverse events were relatively low, a trade-off is necessary between the level of drug exposure required for treatment and safety, and the exposure target (AUC₂₄/MIC) in pediatric patients should be further studied, especially for patients with complications and concomitant medications.

Target Therapeutic Ranges of Anti-MRSA Drugs, Linezolid, Tedizolid and Daptomycin, and the Necessity of TDM

The target therapeutic ranges of vancomycin, teicoplanin, and arbekacin have been determined, and therapeutic drug monitoring (TDM) is performed in clinical practice. However, TDM is not obligatory for daptomycin, linezolid, or tedizolid. In this study, we examined whether TDM will be necessary for these 3 drugs in the future. There was no significant difference in therapeutic effects on acute bacterial skin and skin structure infection between linezolid and tedizolid by meta-analysis. Concerning the therapeutic effects on pneumonia, the rate of effectiveness after treatment with tedizolid was significantly lower than with linezolid. With respect to safety, the incidences of gastrointestinal adverse events and blood/lymphatic system disorders related to tedizolid were significantly lower than those related to linezolid. Linezolid exhibits potent therapeutic effects on pneumonia, but the appearance of adverse reactions is indicated as a problem. There was a dose-dependent decrease in the platelet count, and the target trough concentration (C_trough) was estimated to be 4-6 or 2-7 µg/mL in accordance with the patient's condition. The efficacy of linezolid may be obtained while minimizing the appearance of adverse reactions by performing TDM. The target therapeutic range of tedizolid cannot be achieved in immunocompromised or severe patients. Therefore, we concluded that TDM was unnecessary, considering step-down therapy with oral drugs, use in non-severe patients, and high-level safety. Concerning daptomycin, high-dose administration is necessary to achieve an area under the curve (AUC) of ≥666 as an index of efficacy. To secure its safety, C_trough (<20 µg/mL) monitoring is important. Therefore, TDM is necessary.

Antimicrobial safety considerations in critically ill patients: part II: focused on anti-microbial toxicities

INTRODUCTION

Antibiotic prescription is a challenging issue in critical care settings. Different pharmacokinetic and pharmacodynamic properties, polypharmacy, drug interactions, and high incidence of multidrug-resistant microorganisms in this population can influence the selection, safety, and efficacy of prescribed antibiotics.

AREAS COVERED

In the current article we searched PubMed, Scopus and Google Scholar for neurotoxicities, hematologic toxicity and fluid stewardship in intensive care units.

EXPERT OPINION

Critically ill patients who receive antimicrobial agents should be monitored for neurological, hematologic toxicities especially seizure, thrombocytopenia, and clostridioides infections. Other toxicities including QTc prolongation, electrolyte disturbances, liver enzyme elevation, and infusion-related reactions were being considered. Other changes, including fluid overload, hypoalbuminemia, augmented renal clearance, increased cardiac outputs in septic shock, and acute kidney injury, may influence treatment efficiency and patient outcome.

Renal replacement therapy and concurrent fluconazole therapy increase linezolid-related thrombocytopenia among adult patients

Linezolid has been reported to be associated with thrombocytopenia. However, limited information is available on susceptibility to thrombocytopenia after linezolid usage. We aimed to investigate the risk factors for linezolid-associated thrombocytopenia (LAT). We conducted a retrospective cohort study of patients aged ≥ 18 years who received linezolid for ≥ 5 d during hospitalization in 2019. Information was extracted from electronic medical records. Thrombocytopenia was defined as a platelet count of < 100 × 10⁹/L or a reduction from baseline ≥ 25%. Binary logistic regression and survival analyses were used to evaluate the risk factors for LAT. A total of 98 patients were enrolled. Thrombocytopenia occurred in 53.1% patients, with a median of 9 d after initiation of linezolid. There was no significant difference in the mortality or proportion of platelet transfusions between patients with and without thrombocytopenia. A higher risk of LAT was found in patients who received renal replacement therapy (RRT) (OR 4.8 [1.4–16.4]), or concurrent fluconazole (OR 3.5 [1.2–9.8]). Patients who received RRT (8 vs. 15 d) or concurrent fluconazole (11 vs. 15 d) had a shorter median time to develop thrombocytopenia. Those who simultaneously received RRT and fluconazole had the shortest median of time (6.5 d) and the highest risk of developing thrombocytopenia (87.5%).

A Review of Population Pharmacokinetic Analyses of Linezolid

In recent years, many studies on population pharmacokinetics of linezolid have been conducted. This comprehensive review aimed to summarize population pharmacokinetic models of linezolid, by focusing on dosage optimization to maximize the probability of attaining a certain pharmacokinetic-pharmacodynamic parameter in special populations. We searched the PubMed and EMBASE databases for population pharmacokinetic analyses of linezolid using a parametric non-linear mixed-effect approach, including both observational and prospective trials. Of the 32 studies, 26 were performed in adults, four in children, and one in both adults and children. High between-subject variability was determined in the majority of the models, which was in line with the variability of linezolid concentrations previously detected in observational studies. Some studies found that patients with renal impairment, hepatic failure, advanced age, or low body weight had higher exposure and adverse reactions rates. In contrast, lower concentrations and therapeutic failure were associated with obese patients, young patients, and patients who had undergone renal replacement techniques. In critically ill patients, the inter-individual and intra-individual variability was even greater, suggesting that this population is at an even higher risk of underexposure and overexposure. Therapeutic drug monitoring may be warranted in a large proportion of patients given that the Monte Carlo simulations demonstrated that the one-size-fits-all labeled dosing of 600 mg every 12 h could lead to toxicity or therapeutic failure for high values of the minimum inhibitory concentration of the target pathogen. Further research on covariates, including renal function, hepatic function, and drug–drug interactions related to P-glycoprotein could help to explain variability and improve linezolid dosing regimens.

Parametric Population Pharmacokinetics of Linezolid: A Systematic Review

BACKGROUND

Linezolid is often used for infections caused by drug-resistant Gram-positive bacteria. Recent studies suggest that large between-subject variability (BSV) and within-subject variability could alter drug pharmacokinetics (PK) during linezolid therapy due to pathophysiological changes.

OBJECTIVE

This review synthesized information on linezolid population PK studies and summarized the significant covariates that influence linezolid PK.

METHODS

A literature search was performed using PubMed, Web of Science, and Embase from their inception to 30 September 2021. Published studies were included if they contained data analyzing linezolid PK parameters in humans using a population approach with a nonlinear mixed-effects model.

RESULTS

Twenty-five studies conducted in adults and five in pediatrics were included. One- and two-compartment models were the commonly used structural models for linezolid. Body size (weight, lean body weight, and body surface area), creatinine clearance (CLcr), and age significantly influenced linezolid PK. The median clearance (CL) values (ranges) in infants [0.128 L/h/kg (0.121-0.135)] and children [0.107 L/h/kg (0.088-0.151)] were higher than in adults [0.098 L/h/kg (0.044-0.237)]. For patients with severe renal impairment (CLcr ≤ 30 mL/min), the CL was 37.2% (15.2-55.3%) lower than in patients with normal renal function.

CONCLUSION

The optimal linezolid dosage should be adjusted based on the patient's body size, renal function, and age. More studies are needed to explore the exact mechanism of linezolid elimination and evaluate the PK characteristics in pediatric patients.

Dosage Strategy of Linezolid According to the Trough Concentration Target and Renal Function in Chinese Critically Ill Patients

Background: Linezolid is associated with myelosuppression, which may cause failure in optimally treating bacterial infections. The study aimed to define the pharmacokinetic/toxicodynamic (PK/TD) threshold for critically ill patients and to identify a dosing strategy for critically ill patients with renal insufficiency.

Methods: The population pharmacokinetic (PK) model was developed using the NONMEM program. Logistic regression modeling was conducted to determine the toxicodynamic (TD) threshold of linezolid-induced myelosuppression. The dosing regimen was optimized based on the Monte Carlo simulation of the final model.

Results: PK analysis included 127 linezolid concentrations from 83 critically ill patients at a range of 0.25–21.61 mg/L. Creatinine clearance (CrCL) was identified as the only covariate of linezolid clearance that significantly explained interindividual variability. Thirty-four (40.97%) of the 83 patients developed linezolid-associated myelosuppression. Logistic regression analysis showed that the trough concentration (Cmin) was a significant predictor of myelosuppression in critically patients, and the threshold for Cmin in predicting myelosuppression with 50% probability was 7.8 mg/L. The Kaplan–Meier plot revealed that the overall median time from the initiation of therapy to the development of myelosuppression was 12 days. Monte Carlo simulation indicated an empirical dose reduction to 600 mg every 24 h was optimal to balance the safety and efficacy in critically ill patients with CrCL of 30–60 ml/min, 450 mg every 24 h was the alternative for patients with CrCL &lt;30 ml/min, and 600 mg every 12 h was recommended for patients with CrCL ≥60 ml/min.

Conclusion: Renal function plays a significant role in linezolid PKs for critically ill patients. A dose of 600 mg every 24 h was recommended for patients with CrCL &lt;60 ml/min to minimize linezolid-induced myelosuppression.

Continuous Versus Intermittent Linezolid Infusion for Critically Ill Patients with Hospital-Acquired and Ventilator-Associated Pneumonia: Efficacy and Safety Challenges

High variability of linezolid blood concentrations with partial subtherapeutic levels was observed in critically ill patients who received a standard intravenous dose of linezolid, contributing to drug resistance and toxicity. Continuous infusions of linezolid have been suggested as an alternative and provide good serum and alveolar levels without fluctuations in trough concentration. This study aimed to assess the effectiveness and safety of continuous linezolid infusion versus the standard regimen in critically ill patients. A prospective randomized controlled study was conducted on 179 patients with nosocomial pneumonia. Patients were randomized into two groups. The first group received IV linezolid 600 mg twice daily, while the second group received 600 mg IV as a loading dose, followed by a continuous infusion of 1200 mg/day (50 mg/h) for at least 8−10 days. The continuous infusion group showed a higher clinical cure rate than the intermittent infusion group (p = 0.046). Furthermore, efficacy was proven by greater improvement of P/F ratio (p = 0.030) on day 7 of treatment, a lower incidence of developing sepsis after beginning treatment (p = 0.009), and a shorter time to reach clinical cure (p < 0.001). Hematological parameters were also assessed during the treatment to evaluate the safety between the two groups. The incidence of thrombocytopenia was significantly lower in the continuous infusion group than in the intermittent infusion group. In addition, a stepwise logistic regression model revealed that the intermittent infusion of linezolid was significantly associated with thrombocytopenia (OR =4.128; 95% CI = 1.681−10.139; p =0.001). The current study is the first to assess the clinical aspects of continuous infusion of linezolid beyond pharmacokinetic studies. Continuous infusion of linezolid outperforms intermittent delivery in safety and improves clinical effectiveness in critically ill patients with Gram-positive nosocomial pneumonia.

Initial trough concentration may be beneficial in preventing linezolid-induced thrombocytopenia

We assessed whether prospective therapeutic drug monitoring to optimise the therapeutic range could prevent linezolid-induced thrombocytopenia. This prospective interventional study was conducted from September 2017 to October 2020 among 37 adult patients receiving linezolid. Patients were administered one of the following two initial dosages: 600 mg twice or once daily for patients with a creatinine clearance rate of ≥50 or <50 mL/min, respectively. Linezolid dosage adjustment was performed on days 3-5 based on the trough concentration. The serum linezolid levels in 22 and 15 patients were within and above the therapeutic range (2-7 µg/mL), respectively. The incidence of thrombocytopenia was significantly lower among patients whose linezolid levels were within the therapeutic range (4.5%;1/22) than in those whose levels were above the therapeutic range (80%; 12/15). It is important to maintain the linezolid level within the therapeutic range at the first therapeutic drug monitoring to prevent thrombocytopenia.

Importance and Reality of TDM for Antibiotics Not Covered by Insurance in Japan

Under the Japanese health insurance system, medicines undergoing therapeutic drug monitoring (TDM) can be billed for medical fees if they meet the specified requirements. In Japan, TDM of vancomycin, teicoplanin, aminoglycosides, and voriconazole, which are used for the treatment of infectious diseases, is common practice. This means the levels of antibiotics are measured in-house using chromatography or other methods. In some facilities, the blood and/or tissue concentrations of other non-TDM drugs are measured by HPLC and are applied to treatment, which is necessary for personalized medicine. This review describes personalized medicine based on the use of chromatography as a result of the current situation in Japan.

A Regression Model to Predict Linezolid Induced Thrombocytopenia in Neonatal Sepsis Patients: A Ten-Year Retrospective Cohort Study

Background: Linezolid-induced thrombocytopenia (LIT) is the main factor limiting the clinical application of linezolid (LZD). The incidence and risk factors of LIT in neonatal patients were possibly different from other populations based on pathophysiological characteristics. The purpose of this study was to establish a regression model for predicting LIT in neonatal sepsis patients.

Methods: We retrospectively included 518 patients and divided them into the LIT group and the non-LIT group. A logistic regression analysis was used to analyze the factors related to LIT, and a regression model was established. A receiver operating characteristic (ROC) curve was drawn to evaluate the model’s predictive value. We prospectively collected 39 patients’ data to validate the model and evaluate the effect of LZD pharmacokinetics on LIT.

Results: Among the 518 patients, 103 patients (19.9%) developed LIT. The Kaplan–Meier plot revealed that the overall median time from the initiation of LZD treatment to the onset of LIT in preterm infants was much shorter when compared with term infants [10 (6, 12) vs. 13 (9.75, 16.5), p = 0.004]. Multiple logistic regression analysis indicated that the independent risk factors of LIT were lower weight at medication, younger gestational ages, late-onset sepsis, necrotizing enterocolitis, mechanical ventilation, longer durations of LZD treatment, and lower baseline of platelet level. We established the above seven-variable prediction regression model and calculated the predictive probability. The ROC curve showed that the predicted probability of combined body weight, gestational age, duration of LZD treatment, and baseline of platelet had better sensitivity (84.4%), specificity (74.2%), and maximum AUC (AUC = 0.873). LIT occurred in 9 out of 39 patients (23.1%), and the accuracies of positive and negative predictions of LIT were 88.9 and 76.7%, respectively. Compared with the non-LIT patients, the LIT patients had higher trough concentration [11.49 (6.86, 15.13) vs. 5.51 (2.80, 11.61) mg/L; p = 0.028] but lower apparent volume of distribution (Vd) [0.778 (0.687, 1.421) vs. 1.322 (1.099, 1.610) L; p = 0.010].

Conclusion: The incidence of LIT was high in neonatal sepsis patients, especially in preterm infants. LIT occurred earlier in preterm infants than in term infants. The regression model of seven variables had a high predictive value for predicting LIT. LIT was correlated with higher trough concentration and lower Vd.

Successful treatment of linezolid-induced severe lactic acidosis with continuous venovenous hemodiafiltration: A case report

Linezolid is an oxazolidinone antibiotic. Linezolid-associated lactic acidosis has been reported in 6.8% of linezolid-treated patients. Lactic acidosis is associated with poor clinical outcomes, with high blood lactate levels resulting in organ dysfunction and mortality. This case report describes the development of lactic acidosis in a 64-year-old Chinese woman who had received 33 days of treatment with antituberculosis drugs and 28 days of treatment with oral linezolid for tuberculous meningitis. Severe lactic acidosis was reversed by withdrawing antituberculosis drugs and using continuous venovenous hemodiafiltration (CVVH). When the patient's condition was stable, she was transferred to the infectious disease department, and antituberculosis drugs, with the exception of linezolid, were reintroduced. This did not result in recurrence of lactic acidosis. The causal relationship between lactic acidosis and linezolid was categorized as 'probable' on the Adverse Drug Reaction Probability Scale. This case demonstrates that CVVH has potential as an alternative to discontinuation of linezolid alone for rapid reversal of linezolid-associated severe lactic acidosis.

Therapeutic Drug Monitoring of Antibiotics: Defining the Therapeutic Range

PURPOSE

In the present narrative review, the authors aimed to discuss the relationship between the pharmacokinetic/pharmacodynamic (PK/PD) of antibiotics and clinical response (including efficacy and toxicity). In addition, this review describes how this relationship can be applied to define the therapeutic range of a particular antibiotic (or antibiotic class) for therapeutic drug monitoring (TDM).

METHODS

Relevant clinical studies that examined the relationship between PK/PD of antibiotics and clinical response (efficacy and response) were reviewed. The review (performed for studies published in English up to September 2021) assessed only commonly used antibiotics (or antibiotic classes), including aminoglycosides, beta-lactam antibiotics, daptomycin, fluoroquinolones, glycopeptides (teicoplanin and vancomycin), and linezolid. The best currently available evidence was used to define the therapeutic range for these antibiotics.

RESULTS

The therapeutic range associated with maximal clinical efficacy and minimal toxicity is available for commonly used antibiotics, and these values can be implemented when TDM for antibiotics is performed. Additional data are needed to clarify the relationship between PK/PD indices and the development of antibiotic resistance.

CONCLUSIONS

TDM should only be regarded as a means to achieve the main goal of providing safe and effective antibiotic therapy for all patients. The next critical step is to define exposures that can prevent the development of antibiotic resistance and include these exposures as therapeutic drug monitoring targets.