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

Population pharmacokinetics and thrombocytopenia risk assessment of linezolid in liver transplant recipients

BACKGROUND

Linezolid is a commonly prescribed antibiotic for multidrug-resistant enterococcal infections in liver transplant recipients (LTRs). However, changes in pharmacokinetics due to fluctuations in liver and renal functions, combined with the increased risk of thrombocytopenia, complicate its clinical use. This study aimed to characterize the exposure-thrombocytopenia risk relationship of linezolid in LTRs, and to identify safe dosing thresholds to promote rational drug use.

METHODS

A retrospective analysis was conducted on adult LTRs treated with linezolid at Zhongshan Hospital between January 2019 and May 2022. A population exposure-safety model was developed and used to establish a thrombocytopenia risk threshold and optimize initial dosing strategies through Monte Carlo simulations. An area under the concentration-time curve (AUC) calculator was developed to facilitate individualized dose adjustments.

RESULTS

Exposure-safety analysis revealed that an AUCss,24h threshold of 291.7 mg/L·h was associated with an increased risk of thrombocytopenia. Monte Carlo simulations showed that current covariate-based initial dosing recommendations were suboptimal, highlighting the necessity of therapeutic drug monitoring (TDM) to improve outcomes in LTRs. The online AUC calculator developed in this study offers a practical tool for clinicians to implement timely dose adjustments (https://optimaldose.shinyapps.io/LinezolidAUC/).

CONCLUSIONS

This study provides the first comprehensive analysis of linezolid exposure and its relationship to thrombocytopenia risk in LTRs. The findings underscore the importance of AUC-guided dosing and TDM in optimizing treatment outcomes.

Population pharmacokinetics and clinical assessment of linezolid in pediatric bacterial infections

The pharmacokinetic profile of linezolid still needs further definition, and insufficient or excessive exposure may lead to treatment failure or development of adverse events. Our study aimed to establish a population pharmacokinetic (PPK) model for linezolid in children with bacterial infections, develop an optimal dosage, and evaluate its efficacy and safety. A total of 157 plasma samples from 80 patients were utilized in PPK modeling. A one-compartment model with first-order elimination was most suitable for describing the PK characteristics of linezolid. Weight and creatinine clearance were the significant covariates for clearance. The outcomes of Monte Carlo revealed that in children under 12 years, the probability of target attainment (PTA) for standard dosage (10 mg/kg q8h) was over 90.0% when minimum inhibitory concentration (MIC) ≤2 µg/mL, with a mere 1.4% probability of surpassing the safety threshold. Meanwhile, in children aged 12 years and above, the PTA for standard dosage (600 mg q12h) was over 83.0%, and the probability of surpassing the safety threshold was 0.0%. To take the results one step further, a total of 67 patients (using standard dosage) were enrolled in the efficacy and safety analysis. Of the patients, 95.5% were cured or improved clinical treatment outcomes, and 22.4% of the patients developed possible adverse events (AEs), and no patient experienced early discontinuation of linezolid due to AEs. The standard dosage of linezolid is effective and safe in children with bacterial infections (MIC ≤2 µg/mL). For pathogens with MIC >2 µg/mL, it is advisable to switch antibiotics or increase dosage.CLINICAL TRIALSThis study is registered with Chinese Clinical Trial Registry as ChiCTR 2200061207.

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.

Towards a better detection of patients at-risk of linezolid toxicity in clinical practice: a prospective study in three Belgian hospital centers

Introduction: Linezolid is a last-resort antibiotic for infections caused by multidrug-resistant microorganisms. It is widely used for off-label indications and for longer than recommended treatment durations, exposing patients at higher risk of adverse drug reactions (ADRs), notably thrombocytopenia. This study aimed to investigate ADR incidence and risk factors, identify thrombocytopenia-related trough levels based on treatment duration, and evaluate the performance of predictive scores for ADR development. Methods: Adult in- and outpatients undergoing linezolid therapy were enrolled in three hospitals and ADRs and linezolid trough levels prospectively monitored over time. A population pharmacokinetic (pop-PK model) was used to estimate trough levels for blood samples collected at varying times. Results: A multivariate analysis based on 63 treatments identified treatment duration ≥10 days and trough levels >8 mg/L as independent risk factors of developing thrombocytopenia, with high trough values correlated with impaired renal function. Five patients treated for >28 days did not develop thrombocytopenia but maintained trough values in the target range (<8 mg/L). The Buzelé predictive score, which combines an age-adjusted Charlson comorbidity index with treatment duration, demonstrated 77% specificity and 67% sensitivity to predict the risk of ADR. Conclusion: Our work supports the necessity of establishing guidelines for dose adjustment in patients with renal insufficiency and the systematic use of TDM in patients at-risk in order to keep trough values ≤8 mg/L. The Buzelé predictive score (if ≥7) may help to detect these at-risk patients, and pop-PK models can estimate trough levels based on plasma samples collected at varying times, reducing the logistical burden of TDM in clinical practice.

Rifampicin reduces plasma concentration of linezolid in patients with infective endocarditis

BACKGROUND

Linezolid in combination with rifampicin has been used in treatment of infective endocarditis especially for patients infected with staphylococci.

OBJECTIVES

Because rifampicin has been reported to reduce the plasma concentration of linezolid, the present study aimed to characterize the population pharmacokinetics of linezolid for the purpose of quantifying an effect of rifampicin cotreatment. In addition, the possibility of compensation by dosage adjustments was evaluated.

PATIENTS AND METHODS

Pharmacokinetic measurements were performed in 62 patients treated with linezolid for left-sided infective endocarditis in the Partial Oral Endocarditis Treatment (POET) trial. Fifteen patients were cotreated with rifampicin. A total of 437 linezolid plasma concentrations were obtained. The pharmacokinetic data were adequately described by a one-compartment model with first-order absorption and first-order elimination.

RESULTS

We demonstrated a substantial increase of linezolid clearance by 150% (95% CI: 78%-251%), when combined with rifampicin. The final model was evaluated by goodness-of-fit plots showing an acceptable fit, and a visual predictive check validated the model. Model-based dosing simulations showed that rifampicin cotreatment decreased the PTA of linezolid from 94.3% to 34.9% and from 52.7% to 3.5% for MICs of 2 mg/L and 4 mg/L, respectively.

CONCLUSIONS

A substantial interaction between linezolid and rifampicin was detected in patients with infective endocarditis, and the interaction was stronger than previously reported. Model-based simulations showed that increasing the linezolid dose might compensate without increasing the risk of adverse effects to the same degree.

Astragaloside IV improves the pharmacokinetics of febuxostat in rats with hyperuricemic nephropathy by regulating urea metabolism in gut microbiota

Hyperuricemic nephropathy (HN) is a common clinical complication of hyperuricemia. The pathogenesis of HN is directly related to urea metabolism in the gut microbiota. Febuxostat, a potent xanthine oxidase inhibitor, is the first-line drug used for the treatment of hyperuricemia. However, there have been few studies on the pharmacokinetics of febuxostat in HN animal models or in patients. In this study, a high-purine diet-induced HN rat model was established. The pharmacokinetics of febuxostat in HN rats was evaluated using LC-MS/MS. Astragaloside IV (AST) was used to correct the abnormal pharmacokinetics of febuxostat. Gut microbiota diversity analysis was used to evaluate the effect of AST on gut microbiota. The results showed that the delayed elimination of febuxostat caused drug accumulation after multiple administrations. Oral but not i. p. AST improved the pharmacokinetics of febuxostat in HN rats. The mechanistic study showed that AST could regulate urea metabolism in faeces and attenuate urea-ammonia liver-intestine circulation. Urease-related genera, including Eubacterium, Parabacteroides, Ruminococcus, and Clostridia, decreased after AST prevention. In addition, the decrease in pathogenic genera and increase in short-chain fatty acids (SCFA) producing genera also contribute to renal function recovery. In summary, AST improved the pharmacokinetics of febuxostat in HN rats by comprehensive regulation of the gut microbiota, including urea metabolism, anti-calcification, and short-chain fatty acid generation. These results imply that febuxostat might accumulate in HN patients, and AST could reverse the accumulation through gut microbiota regulation.

Linezolid Administration to Critically Ill Patients: Intermittent or Continuous Infusion? A Systematic Literature Search and Review

A judicious antibiotic therapy is one of the challenges in the therapy of critically ill patients with sepsis and septic shock. The pathophysiological changes in these patients significantly alter the antibiotic pharmacokinetics (PK) and pharmacodynamics (PD) with important consequences in reaching the therapeutic targets or the risk of side effects. The use of linezolid, an oxazolidinone antibiotic, in intensive care is such an example. The optimization of its therapeutic effects, administration in intermittent (II) or continuous infusion (CI) is gaining increased interest. In a systematic review of the main databases, we propose a detailed analysis of the main PK/PD determinants, their relationship with the clinical therapeutic response and the occurrence of adverse effects following II or CI of linezolid to different classes of critically ill patients or in Monte Carlo simulations.