Pharmacokinetics/pharmacodynamics of polymyxin B in patients with bloodstream infection caused by carbapenem-resistant Klebsiella pneumoniae

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.

Polymyxins: recent advances and challenges

Antibiotic resistance is a pressing global health challenge, and polymyxins have emerged as the last line of defense against multidrug-resistant Gram-negative (MDR-GRN) bacterial infections. Despite the longstanding utility of colistin, the complexities surrounding polymyxins in terms of resistance mechanisms and pharmacological properties warrant critical attention. This review consolidates current literature, focusing on polymyxins antibacterial mechanisms, resistance pathways, and innovative strategies to mitigate resistance. We are also investigating the pharmacokinetics of polymyxins to elucidate factors that influence their in vivo behavior. A comprehensive understanding of these aspects is pivotal for developing next-generation antimicrobials and optimizing therapeutic regimens. We underscore the urgent need for advancing research on polymyxins to ensure their continued efficacy against formidable bacterial challenges.

Pharmacokinetics of polymyxin B in different populations: a systematic review

BACKGROUND AND OBJECTIVES

Despite being clinically utilized for the treatment of infections, the limited therapeutic range of polymyxin B (PMB), along with considerable interpatient variability in its pharmacokinetics and frequent occurrence of acute kidney injury, has significantly hindered its widespread utilization. Recent research on the population pharmacokinetics of PMB has provided valuable insights. This study aims to review relevant literature to establish a theoretical foundation for individualized clinical management.

METHODS

Follow PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, Pop-PK studies of PMB were searched in PubMed and EMBASE database systems from the inception of the database until March 2023.

RESULT

To date, a total of 22 population-based studies have been conducted, encompassing 756 subjects across six different countries. The recruited population in these studies consisted of critically infected individuals with multidrug-resistant bacteria, patients with varying renal functions, those with cystic fibrosis, kidney or lung transplant recipients, patients undergoing extracorporeal membrane oxygenation (ECMO) or continuous renal replacement therapy (CRRT), as well as individuals with obesity or pediatric populations. Among these studies, seven employed a one-compartmental model, with the range of typical clearance (CL) and volume (Vc) being 1.18-2.5L /h and 12.09-47.2 L, respectively. Fifteen studies employed a two-compartmental model, with the ranges of the clearance (CL) and volume of the central compartment (Vc), the volume of the peripheral compartment (Vp), and the intercompartment clearance (Q) were 1.27-8.65 L/h, 5.47-38.6 L, 4.52-174.69 L, and 1.34-24.3 L/h, respectively. Primary covariates identified in these studies included creatinine clearance and body weight, while other covariates considered were CRRT, albumin, age, and SOFA scores. Internal evaluation was conducted in 19 studies, with only one study being externally validated using an independent external dataset.

CONCLUSION

We conclude that small sample sizes, lack of multicentre collaboration, and patient homogeneity are the primary reasons for the discrepancies in the results of the current studies. In addition, most of the studies limited in the internal evaluation, which confined the implementation of model-informed precision dosing strategies.

Clinical Efficacy and Safety of Colistin Sulfate in the Treatment of Carbapenem-Resistant Organism Infections in Patients with Hematological Diseases

INTRODUCTION

Carbapenem-resistant organisms (CRO) have emerged as a significant worldwide issue. However, the availability of efficacious antibiotics for treating CRO infections remains limited. Polymyxins, including colistin sulfate, represent the last-line therapeutic option against CRO infections. This study aims to retrospectively evaluate the clinical effectiveness and safety of colistin sulfate in managing CRO infections among patients with hematological diseases.

METHODS

Between April 2022 and January 2023, a total of 118 hematological patients diagnosed with CRO infection were treated with colistin sulfate at Suzhou Hongci Hospital of Hematology. The assessment encompassed the clinical efficacy, bacterial clearance rate, adverse reactions, and 30-day all-cause mortality.

RESULTS

The study found that the total effective rate of colistin sulfate in the treatment of CRO infection was 74.6%, with a bacterial clearance rate of 72.6%. Throughout the treatment, nephrotoxicity occurred in 7.6% of cases, neurotoxicity in 2.5% of cases, and the 30-day all-cause mortality rate was 22.9%. Multivariate logistic analysis revealed that the treatment course and combination medication with other antimicrobials were independent factors affecting the clinical efficacy of colistin sulfate.

CONCLUSION

Our study demonstrates that the treatment of colistin sulfate can achieve high clinical efficacy and microbial responses, with a low risk of nephrotoxicity. This study provides evidence of the positive clinical efficacy and safety of colistin sulfate treatment in these patients. High-quality randomized controlled trials are still needed to further confirm the beneficial role of colistin sulfate.

Evaluation of polymyxin B AUC/MIC ratio for dose optimization in patients with carbapenem-resistant Klebsiella pneumoniae infection

Polymyxin B has been used as a last-line therapy for the treatment of carbapenem-resistant gram-negative bacterial infection. The pharmacokinetic/pharmacodynamic index (AUC/MIC) of polymyxin B has not been clinically evaluated, given that the broth microdilution method for polymyxin susceptibility testing is rarely used in hospitals. This study analyzed data from 77 patients with carbapenem-resistant Klebsiella pneumoniae infections. Among the samples, 63 K. pneumoniae isolates had MIC values of 1.0 mg/L as measured by broth microdilution but 0.5 mg/L as measured using the Vitek 2 system. Polymyxin B AUC/MIC was significantly associated with clinical response (p = 0.002) but not with 30-day all-cause mortality (p = 0.054). With a target AUC/MIC value of 50, Monte Carlo simulations showed that a fixed dose of 100 mg/12 h and three weight-based regimens (1.25 mg/kg/12 h for 80 kg and 1.5 mg/kg/12 h for 70 kg/80 kg) achieved a cumulative fraction of response >90% regardless of renal function, but the risk of nephrotoxicity was high. For patients with carbapenem-resistant K. pneumoniae infections, the underestimation of polymyxin resistance in automated systems need to be taken into account when optimizing polymyxin B dosing based on pharmacokinetic/pharmacodynamic principles.

Pharmacokinetics of Antibacterial Agents in the Elderly: The Body of Evidence

Infections are important factors contributing to the morbidity and mortality among elderly patients. High rates of consumption of antimicrobial agents by the elderly may result in increased risk of toxic reactions, deteriorating functions of various organs and systems and leading to the prolongation of hospital stay, admission to the intensive care unit, disability, and lethal outcome. Both safety and efficacy of antibiotics are determined by the values of their plasma concentrations, widely affected by physiologic and pathologic age-related changes specific for the elderly population. Drug absorption, distribution, metabolism, and excretion are altered in different extents depending on functional and morphological changes in the cardiovascular system, gastrointestinal tract, liver, and kidneys. Water and fat content, skeletal muscle mass, nutritional status, use of concomitant drugs are other determinants of pharmacokinetics changes observed in the elderly. The choice of a proper dosing regimen is essential to provide effective and safe antibiotic therapy in terms of attainment of certain pharmacodynamic targets. The objective of this review is to perform a structure of evidence on the age-related changes contributing to the alteration of pharmacokinetic parameters in the elderly.

The dilemma of antibiotic susceptibility and clinical decision-making in a multi-drug-resistant Pseudomonas aeruginosa bloodstream infection

Objective: How to choose the appropriate antibiotics and dosage has always been a difficult issue during the treatment of multi-drug-resistant bacterial infections. Our study aims to resolve this difficulty by introducing our multi-disciplinary treatment (MDT) clinical decision-making scheme based on rigorous interpretation of antibiotic susceptibility tests and precise therapeutic drug monitoring (TDM)-guided dosage adjustment. Method: The treatment course of an elderly patient who developed a multi-drug-resistant Pseudomonas aeruginosa (MDRPA) bloodstream infection from a brain abscess was presented. Results: In the treatment process, ceftazidime-avibactam (CAZ-AVI) was used empirically for treating the infection and clinical symptoms improved. However, the follow-up bacterial susceptibility test showed that the bacteria were resistant to CAZ-AVI. Considering the low fault tolerance of clinical therapy, the treatment was switched to a 1 mg/kg maintenance dose of susceptible polymyxin B, and TDM showed that the AUC_{24h, ss} of 65.5 mgh/L had been achieved. However, clinical symptoms were not improved after 6 days of treatment. Facing the complicated situation, the cooperation of physicians, clinical pharmacologists, and microbiologists was applied, and the treatment finally succeeded with the pathogen eradicated when polymyxin B dose was increased to 1.4 mg/kg, with the AUC_{24h, ss} of 98.6 mgh/L. Conclusion: MDT collaboration on the premise of scientific and standardized drug management is helpful for the recovery process in patients. The empirical judgment of doctors, the medication recommendations from experts in the field of TDM and pharmacokinetics/pharmacodynamics, and the drug susceptibility results provided by the clinical microbiology laboratory all provide the direction of treatment.