A population pharmacokinetic model of polymyxin B based on prospective clinical data to inform dosing in hospitalized patients

Population pharmacokinetics study on nebulized and intravenous administration of polymyxin B in patients with pneumonia caused by multidrug-resistant gram-negative bacteria

Polymyxin B (PMB) remains a last-line therapeutic agent for multidrug-resistant gram-negative bacteria (MDR-GNB) infections. However, reliable pharmacokinetic (PK) data to guide nebulized PMB dosing regimens in critically ill patients are limited. This study aimed to establish a population pharmacokinetic (PopPK) model for PMB in both epithelial lining fluid (ELF) and plasma of critically ill patients with MDR-GNB pneumonia and to optimize dosing regimens. A prospective PK study was conducted in 76 adult patients receiving nebulized PMB either as monotherapy or in combination with intravenous administration. PK data were analyzed using non-linear mixed-effect modeling, with PMB concentration-time profiles described by a coupled model integrating separate two-compartment models for plasma and ELF. The final model identified albumin levels and age as significant covariates influencing PK variability. Monte Carlo simulations demonstrated that nebulization therapy either alone or combined with intravenous administration significantly enhances ELF concentration and the probability of target attainment. Additionally, Pseudomonas aeruginosa requires higher nebulized doses than Klebsiella pneumoniae and Acinetobacter baumannii. This study develops a PopPK model of PMB in ELF and plasma, providing critical insights to optimize PMB treatment strategies for patients with MDR-GNB pneumonia.

Real-world performance in therapeutic target attainment of various recommended polymyxin B dose regimens: secondary data analysis of a prospective multicenter cohort

BACKGROUND

Various population pharmacokinetic studies have suggested controversial optimal dosing regimens for polymyxin B in recent years. The objective of this study was to examine the real-world performance of various dosing regimens in therapeutic target attainment.

METHODS

This is a secondary analysis of a large prospective multicenter cohort (ChiCTR2200056667). Patients were retrospectively included from the cohort, and patient demographic characteristics, polymyxin B dosing regimens and corresponding 24-hour areas under the curve (AUCs) were collected. Patients were categorized into various groups according to the dosage regimens, and the corresponding AUC target attainment was analyzed. The target AUC ratio was defined as 50-100 mg/L∙h.

RESULTS

A total of 304 AUC data from 247 patients were included in this study. Only 55.3% of the AUCs were in the range of 50-100 mg/L∙h. Differences in subgroups stratified by fixed-dosing regimens, weight-based regimens, and renal function-based dosing regimens. Moreover, the differences among the highest target dose strategies (fixed dose of 50 mg/12 h, weight-adjusted dose of 1-1.25 mg/kg/12 h, and CRRT unadjusted dose) were also insignificant.

CONCLUSION

No polymyxin B dosing strategy is superior in terms of target attainment, which highlights the importance of TDM in the clinical application of polymyxin B.

Biomarker-Driven Pharmacokinetics and Efficacy of Polymyxin B in Critically Ill Patients with XDR-GN Pneumonia

Background: Achieving pharmacokinetic/pharmacodynamic (PK/PD) targets is critical for improving treatment success, particularly in critically ill patients. This study investigates the role of inflammatory biomarkers and their influence on the PK/PD characteristics of polymyxin B (PMB) in patients with extensively drug-resistant Gram-negative (XDR-GN) bacterial nosocomial pneumonia. Methods: Serial blood and/or bronchoalveolar lavage fluid (BALF) samples were collected at specified time points and analyzed for PMB and/or inflammatory biomarkers, including IL-6 and IL-10. Clinical data were also recorded, and their correlations with PK parameters were further analyzed. Results: Among the 27 enrolled patients, 22 (81.5%) achieved treatment success. The pharmacokinetic parameters of PMB included a maximum plasma concentration (Cmax) of 8.3 µg/mL, clearance (CL) of 1.55 L/h, volume of distribution (Vd) of 30.44 L, half-life (t1/2) of 19.56 h, steady-state area under the plasma concentration-time curve from time 0 to 24 h (AUCss,0-24h) of 110.08 h·µg/mL, and a plasma protein-binding ratio of 85.53%. The AUCss,0-24h metric was identified as a robust predictor of clinical efficacy, with an optimal cutoff value of 77.27 h·µg/mL. Notably, 48.15% of patients achieved the target AUCss,0-24h range of 50-100 h·µg/mL, with 76.95% of these patients attaining treatment success. Another 48.15% of patients exceeded this target, and 92.31% of this subgroup achieved treatment success. PMB demonstrated limited pulmonary penetration, with an epithelial lining fluid (ELF)/plasma ratio of 15.69% [16.86, 18.15]. Furthermore, TNF-α and the IL-6/IL-10 ratio were significantly correlated with PMB PK parameters. Conclusions: Our and others' studies suggest heterogeneity of PMB PK parameters in critically ill patients. The majority of critically ill patients achieved or surpassed the recommended PK/PD targets and attained treatment success through intravenous administration of PMB at a simplified fixed dose. However, PMB did not achieve satisfactory pulmonary concentrations, suggesting that its efficacy may involve alternative mechanisms. The modulation of inflammatory responses may play a pivotal role in the treatment of severe infections, highlighting the potential for biomarker-guided therapeutic strategies.

Clinical outcomes and pharmacokinetics/pharmacodynamics of intravenous polymyxin B treatment for various site carbapenem-resistant gram-negative bacterial infections: a prospective observational multicenter study

Polymyxin B, a last resort for carbapenem-resistant gram-negative bacteria (CRGNB) infections, has infection site-specific pharmacokinetic/pharmacodynamic (PK/PD) properties. However, there is little clinical evidence to support optimal exposures of polymyxin B for different site infections. We performed a prospective, observational, multicenter study to evaluate the clinical outcomes and PK/PD of intravenous polymyxin B treatment for various site CRGNB infections. The main clinical outcomes were 14-day all-cause mortality and nephrotoxicity, and the secondary outcomes were 28-day mortality and clinical response. The area under curves (AUCs) of polymyxin B were determined, and their associations with clinical outcomes were analyzed by stratification based on the infection site. A total of 312 patients were ultimately enrolled from 10 research centers. The overall 14-day mortality was 29.5%, and those of patients with lower respiratory tract infection (LRTI), intra-abdominal infection (IAI), and bloodstream infection (BSI) were 32.3%, 19.7%, and 30.3%, respectively. The 28-day mortality rate was 38.1%, while LRTI patients had the highest mortality (41.4%) and IAI patients lowest (34.8%). The clinical response rate was 46.2%, which was similar among the subgroups. The overall AKI rate was 60.9%. An AUC greater than 50 mg∙h/L was related to lower mortality in IAI patients but not in LRTI patients, which led to a lower but not significant difference in the overall analysis. The AUC of polymyxin B was an independent risk factor for 14-day mortality in IAI patients, and the cutoff value was 76 mg∙h/L. The results would be helpful for personalized dosing and monitoring of polymyxin B.CLINICAL TRIALSThis study is registered with the Chinese Clinical Trial Registry as ChiCTR2200056667.

Monte Carlo simulation to optimize polymyxin B dosing regimens for the treatment of Gram-negative bacteremia

Objective

This study aimed to predict and evaluate the efficacy of various polymyxin B dosing regimens for Gram-negative bacteremia using Monte Carlo simulation, with a specific focus on assessing the efficacy in patients receiving continuous renal replacement therapy (CRRT). The goal was to optimize clinical dosing regimens and guide rational polymyxin B use in practice.

Methods

A total of 1,939 Gram-negative bacterial strains were analyzed, collected between April 2019 and December 2021 through the China Bloodstream Gram-negative Pathogens Antimicrobial Resistance and Virulence Surveillance Network (CARVIS-NET). Pharmacokinetic parameters of polymyxin B from existing literature were used to conduct a Monte Carlo simulation based on pharmacokinetic/pharmacodynamic (PK/PD) theory. The probability of target attainment (PTA) and cumulative fraction of response (CFR) were evaluated across various dosing regimens.

Results

The main pathogens of Gram-negative bacteremia were Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii, all of which demonstrated high susceptibility to polymyxin B. For pathogens with a minimum inhibitory concentration (MIC) ≤1 mg/L, all regimens achieved PTA >90%. However, when the MIC increased to 2 mg/L, the PTA for the 500,000 IU q12h regimen decreased to 77.53%, and at an MIC of 4 mg/L, none of the dosing regimens achieved a PTA >90%. For P. aeruginosa and K. pneumoniae with MIC ≤0.5 mg/L, all regimens demonstrated effectiveness. However, at MIC ≥1 mg/L, significant declines in PTA were observed, with the 500,000 IU q12h and 1.25 mg/kg q12h regimens yielding suboptimal outcomes. In CRRT patients, PTA values declined further, particularly against K. pneumoniae, raising concerns about potential treatment failure.

Conclusion

Polymyxin B demonstrates high efficacy for Gram-negative bacteremia with MIC ≤1 mg/L. However, efficacy diminishes as MIC increases, particularly for P. aeruginosa and K. pneumoniae, where 500,000 IU q12h and 1.25 mg/kg q12h regimens may result in suboptimal outcomes. For CRRT patients with K. pneumoniae bacteremia, therapeutic drug monitoring and dose adjustments are crucial to mitigate treatment failure risks.

Population pharmacokinetic analysis and dosing optimization of colistin sulphate in lung transplant recipients with pneumonia: A prospective study

OBJECTIVE

Currently, there is a lack of information on the clinical pharmacokinetics (PK), effectiveness, and safety of colistin sulphate (CS) in lung transplant recipients. This study aims to improve CS dosing regimens and evaluate its population PK in lung transplant recipients.

METHODS

This study evaluated the clinical efficacy, microbiological efficacy, and adverse events of CS in lung transplant recipients. The NONMEM program was employed to construct the population PK model, and Monte Carlo simulations were executed to establish dosing regimens according to the probability of target attainment (PTA).

RESULTS

The study included 146 CS concentrations, spanning from 0.05 to 4.18 mg/L from 39 lung transplant recipients with multidrug-resistant Gram-negative bacteria. 26 (66.67%) patients successfully eradicated bacteria, and 30 (76.92%) patients had clinical cure or improvement. Additionally, only 2 (5.13%) patients developed CS-related nephrotoxicity. The PK profile was effectively represented by a one-compartmental model with linear elimination. Creatinine clearance and concomitant furosemide use were recognized as covariates influencing the clearance of CS. Based on the PTA results, a daily dosage of 1.5 million IU, divided into 2-3 administrations, could attain a PTA exceeding 90% for MIC ≤ 1 µg/mL at creatinine clearance of about 110 mL/min. However, this regimen would lead to insufficient exposure for MIC ≥ 2 µg/mL.

CONCLUSIONS

The clearance of CS is significantly influenced by concomitant furosemide use and renal function. The currently recommended dosing regimens by label sheet may result in subtherapeutic exposure for MIC exceeding 1 mg/L in lung transplant recipients.

A simple HPLC-MS/MS method for the determination of polymyxin B in human plasma and its application in the pharmacokinetic study in elderly patients infected with multidrug-resistant Gram-negative bacteria

Introduction: Polymyxin B is widely used to treat infections caused by multidrug-resistant Gram-negative bacteria. However, the pharmacokinetic study data of PB in the elderly are scarce. Herein, a simple method to measure the concentration of PB in human plasma was developed and validated by high performance liquid chromatography-tandem mass spectrometry, and it was applied to a PK study in the elderly. Methods: PB was extracted from human plasma by a rapid protein-precipitation method using 0.1% formic acid in methanol and then separated on an ultimate AQ-C18 column using linear gradient elution with a 0.5-mL/min flow rate. Subsequently, PB was detected using a mass spectrometer operated in positive-ion and multiple-reaction-monitoring modes. Results: The lower limits of quantification of the method for Polymyxin B1 and Polymyxin B2 were 1.00 and 0.10 μg/mL, respectively. The linear ranges for PB1 and PB2 were 1.00-20.02 and 0.10-2.04 μg/mL, respectively. Patients receiving a 75-mg maintenance dose every 12h had AUCss, 24 h, and Css, av values of 117.70 ± 37.03 μg h/mL and 4.14 ± 1.74 μg/mL, respectively. For patients receiving a 100 mg maintenance dose, these values were 152.73 ± 70.09 μg h/mL and 5.43 ± 2.85 μg/mL, respectively. Conclusion: The validated HPLC-MS/MS method was successfully applied to a study on the pharmacokinetics of PB in elderly patients infected with multidrug-resistant Gram-negative bacteria. Both two dose strategies in this study would have a excessive PB exposure in the elderly patients then the therapeutic window recommended by guidelines.

Efficacy and Safety Factors Related to Plasma Concentration-Optimized Polymyxin B Therapy in Treating Carbapenem-Resistant Gram-Negative Bacterial Infections in China

Background

Polymyxin B (PMB)-based combination therapies are used to treat severe carbapenem-resistant gram-negative bacterial (CR-GNB) infections. This observational study investigated the relationship between clinical factors, including PMB concentration, and clinical efficacy and safety.

Patients and Methods

Polymyxin B regimens were optimized through therapeutic drug monitoring (TDM) and area under the concentration-time curve (AUC). In all, 382 samples were tested from 130 patients. Logistic regression was used to analyze the relationships between variables with clinical efficacy and 30-day mortality factors were analyzed by Cox regression. The sensitivity and specificity of Cmin and AUC for the occurrence of acute kidney injury (AKI) were determined by ROC curve analysis.

Results

The clinical effectiveness of PMB was 65.4%. Multivariate logistic regression analysis revealed that lung infection, continuous renal replacement therapy, and C-reactive protein were independent factors significantly associated with efficacy. AKI occurred in 14.6% of the patients during treatment; age > 73 years (OR: 3.63; 95% CI: 1.035-12.727; P = 0.044), Cmin greater than 2.3 µg/mL (OR: 7.37; 95% CI: 1.571-34.580; P = 0.011), combined vancomycin (OR: 9.47; 95% CI: 1.732-51.731; P = 0.009), and combined piperacillin-tazobactam (OR: 21.87; 95% CI: 3.139-152.324; P = 0.002) were independent risk factors. The identified PMB cut-offs for predicting AKI were Cmin = 2.3 µg/mL and AUC = 82.0 mg h/L.

Conclusion

Polymyxin B-based combination regimens are effective in treating CR-GNB infections, particularly bloodstream infections, but have shown unsatisfactory for lung infections. Cmin ≥ 2.3 µg /mL and AUC ≥ 82.0 mg h/L may increase PMB-associated AKI incidence. PMB dose should be adjusted based on TDM to ensure efficacy.

Daily fluid intake as a novel covariate affecting the population pharmacokinetics of polymyxin B in patients with sepsis

BACKGROUND

Polymyxin B dosing in patients with sepsis is difficult because pathophysiological changes and supportive therapies alter drug pharmacokinetics (PK). This study aimed to investigate the impact of fluid management and renal function on the PK of polymyxin B and to propose alternative dosing regimens.

METHODS

Patients (aged ≥ 18 y) with sepsis and receiving intravenous polymyxin B for ≥ 96 h were enrolled. Blood samples were collected at steady state. Plasma concentrations were measured by liquid chromatography-tandem mass spectrometry and subjected to population PK modelling. Monte Carlo simulations were used to optimise dosage regimens.

RESULTS

Eighty-three patients with a median (range) daily fluid intake of 4.2 (1.3-8.4) L and a creatinine clearance (CrCL) of 87.5 (17.3-309.7) mL/min were included. Polymyxin B PK was adequately characterised by a two-compartment model. The PK covariate analysis revealed daily fluid intake statistically significantly affected central volume of distribution and central compartment clearance (CL), and CrCL influenced CL. Simulation indicated that a decreased dosing would be suitable for patients with renal dysfunction (CrCL < 40 mL/min), and therapeutic drug monitoring is recommended to avoid exposure fluctuation when patients have fluid overload.

CONCLUSIONS

Fluid management as well as renal function are essential factors affecting polymyxin B PK for patients with sepsis, which can help optimise dosage regimens.

Prevention and management of antibiotic associated acute kidney injury in critically ill patients: new insights

PURPOSE OF REVIEW

Drug associated kidney injury (D-AKI) occurs in 19-26% of hospitalized patients and ranks as the third to fifth leading cause of acute kidney injury (AKI) in the intensive care unit (ICU). Given the high use of antimicrobials in the ICU and the emergence of new resistant organisms, the implementation of preventive measures to reduce the incidence of D-AKI has become increasingly important.

RECENT FINDINGS

Artificial intelligence is showcasing its capabilities in early recognition of at-risk patients for acquiring AKI. Furthermore, novel synthetic medications and formulations have demonstrated reduced nephrotoxicity compared to their traditional counterparts in animal models and/or limited clinical evaluations, offering promise in the prevention of D-AKI. Nephroprotective antioxidant agents have had limited translation from animal studies to clinical practice. The control of modifiable risk factors remains pivotal in avoiding D-AKI.

SUMMARY

The use of both old and new antimicrobials is increasingly important in combating the rise of resistant organisms. Advances in technology, such as artificial intelligence, and alternative formulations of traditional antimicrobials offer promise in reducing the incidence of D-AKI, while antioxidant medications may aid in minimizing nephrotoxicity. However, maintaining haemodynamic stability using isotonic fluids, drug monitoring, and reducing nephrotoxic burden combined with vigilant antimicrobial stewardship remain the core preventive measures for mitigating D-AKI while optimizing effective antimicrobial therapy.

Population pharmacokinetics of polymyxin B in patients with liver dysfunction

AIMS

Polymyxin B (PMB) is widely used to treat infections caused by multidrug-resistant Gram-negative pathogens. Currently, the pharmacokinetic data of PMB in patients with liver dysfunction are limited. This study aimed to develop a population pharmacokinetic (PopPK) model of PMB in patients with liver dysfunction and identify the factors affecting PMB pharmacokinetics.

METHODS

We conducted a retrospective pharmacokinetic study involving 136 adults with different levels of liver function. Nonlinear mixed effects modelling was used to develop a PopPK model of PMB. Monte Carlo simulation was used to design PMB dosage schedules across various liver and renal functions.

RESULTS

PMB pharmacokinetic analyses included 401 steady-state concentrations in 136 adult patients. A one-compartment pharmacokinetic model with first-order absorption and elimination was used to describe the data. The typical population value of PMB clearance was 2.43 L/h and the volume of distribution was 23.11 L. This study revealed that creatinine clearance (CrCL) and Child-Pugh class were significantly associated with PMB pharmacokinetic parameters; however, clinically relevant variations of dose-normalized drug exposure were not significant. For patients with a minimum inhibitory concentration of ≤0.5 mg/L, the appropriate dose was 40-75 mg/12-h. When the dose exceeded 100 mg/12-h, the risk of nephrotoxicity increased significantly.

CONCLUSIONS

This study provided PMB pharmacokinetic information for patients with liver dysfunction. Patients with renal and liver dysfunctions may not require an initial dose adjustment. Rather than PopPK-guided dose adjustment, therapeutic drug monitoring of PMB plays a more direct role in optimizing dosing regimens based on its therapeutic window.