Effectiveness and tolerability of a polymyxin B dosing protocol

Mid-dosing interval concentration is important for polymyxin B exposure and acute kidney injury in critically ill patients

This study aimed to evaluate the association between polymyxin B (PMB) exposure and acute kidney injury (AKI) and analyze the risk factors for PMB-induced AKI in critically ill patients. Plasma concentrations of PMB were determined using an ultraperformance liquid chromatography-tandem mass spectrometer in intensive care unit patients who were administered PMB. Univariate and multivariate analyses were conducted to identify risk factors. A receiver operating characteristic curve was constructed to assess the discriminant power of the factors and to identify the cutoff value for AKI. The white blood cell count and estimated area under the concentration-time curve (AUC) of patients administered PMB were independent risk factors for PMB-induced AKI, where AUC were calculated using a first-order pharmacokinetic equation based on the mid-dosing interval concentration (C1/2t ) and peak concentration. The area under the receiver operating characteristic curve of the final model was 0.805 (95% confidence interval, 0.690-0.921). The cutoff value for the combined predictor was 0.57. Alternatively, when using C1/2t , which was strongly correlated with AUC, as the only independent risk factor, the analysis showed that the 3.47 μg/ml threshold provides favorable differentiation between the AKI and non-AKI groups. These results provide insightful information for therapeutic drug monitoring-guiding PMB dosing in clinical practice.

Population pharmacokinetics and limited sampling strategies of polymyxin B in critically ill patients

OBJECTIVES

To characterize the pharmacokinetics (PK) of polymyxin B in Chinese critically ill patients. The factors significantly affecting PK parameters are identified, and a limited sampling strategy for therapeutic drug monitoring of polymyxin B is explored.

METHODS

Thirty patients (212 samples) were included in a population PK analysis. A limited sampling strategy was developed using Bayesian estimation, multiple linear regression and modified integral equations. Non-linear mixed-effects models were developed using Phoenix NLME software.

RESULTS

A two-compartment population PK model was used to describe polymyxin B PK. Population estimates of the volumes of central compartment distribution (V) and peripheral compartment distribution (V2), central compartment clearance (CL) and intercompartmental clearance (Q) were 7.857 L, 12.668 L, 1.672 L/h and 7.009 L/h. Continuous renal replacement therapy (CRRT) significantly affected CL, and body weight significantly affected CL and Q. The AUC0-12h of polymyxin B in patients with CRRT was significantly lower than in patients without CRRT. CL and Q increased with increasing body weight. A limited sampling strategy was suggested using a two-sample scheme with plasma at 0.5h and 8h after the end of infusion (C0.5 and C8) for therapeutic drug monitoring in the clinic.

CONCLUSIONS

A dosing regimen should be based on body weight and the application of CRRT. A two-sample strategy for therapeutic drug monitoring could facilitate individualized treatment with polymyxin B in critically ill patients.

Does Monitoring Total and Free Polymyxin B1 Plasma Concentrations Predict Polymyxin B-Induced Nephrotoxicity? A Retrospective Study in Critically Ill Patients

INTRODUCTION

The correlation between total and free polymyxin B (PMB including PMB1 and PMB2) exposure in vivo and acute kidney injury (AKI) remains obscure. This study explores the relationships between plasma exposure of PMB1 and PMB2 and nephrotoxicity, and investigates the risk factors for PMB-induced acute kidney injury (AKI) in critically ill patients.

METHODS

Critically ill patients who used PMB and met the criteria were enrolled. The total plasma concentration and plasma binding of PMB1 and PMB2 were analysed by liquid chromatography-tandem mass spectrometry and equilibrium dialysis.

RESULTS

A total of 89 patients were finally included, and AKI developed in 28.1% of them. The peak concentration of PMB1 (C_max (B1)) (adjusted odds ratio (AOR) = 1.68, 95% CI 1.08-2.62, p = 0.023), baseline BUN level (AOR = 1.08, 95% CI 1.01-1.16, p = 0.039) and hypertension (AOR = 3.73, 95% CI 1.21-11.54, p = 0.022) were independent risk factors for PMB-induced AKI. The area under the ROC curve of the model was 0.799. When C_max (B1) was 5.23 μg/ml or more, the probability of AKI was higher than 50%. The ratio of PMB1/PMB2 decreased after PMB preparation entered into the body. The protein binding rate in critically ill patients indicated significant individual differences. Free C_max (B) and free C_max (B1) levels in the AKI group were significantly (p < 0.05) higher than those in the non-AKI group. Total and free concentrations of PMB in patients showed a positive correlation.

CONCLUSIONS

Both the ROC curve and logistic regression model showed that C_max (B1) was a good predictor for the probability of PMB-induced AKI. Early therapeutic drug monitoring (TDM) of PMB should be considered in critically ill patients. Compared with C_min (B), C_max (B) and C_max (B1) may be helpful for the early prediction of PMB-induced AKI in critically ill patients.

Risk of polymyxin B-induced acute kidney injury with a non adjusted dose versus adjusted dose based on renal function

Aim: To observe the difference in the risk of polymyxin B (PMB)-induced acute kidney injury (AKI) with or without dose adjustment based on the patients renal function. Materials & methods: This retrospective cohort analysis was carried out in 115 patients treated with PMB from November 2018 to October 2019. Results: No significant difference in the incidence of AKI as well as secondary outcomes was observed between these two groups (47.5 vs 37.14%; p = 0.304). Conclusion: Dosing adjustment based on renal function does not significantly lower the risk of PMB-induced AKI. A non adjusted dosing strategy for PMB is recommended in patients exhibiting various levels of renal impairment.

Trough polymyxin B plasma concentration is an independent risk factor for its nephrotoxicity

AIMS

Data regarding clinical pharmacokinetic/toxicodynamic (PK/TD) of polymyxin B is short of direct quantitative data. This study aims to investigate the risk factors of polymyxin B associated acute kidney injury (AKI) and to assess the relationship between polymyxin B plasma levels and its nephrotoxicity.

METHODS

A retrospective study was performed in adult patients treated with polymyxin B. Risk factors associated with AKI and plasma trough concentrations of polymyxin B were identified via medical record review. A multivariate logistic regression model was established and the risk of polymyxin B-associated AKI were predicted by a receiver operating characteristic curve, with maximal Youden index used to identify safety thresholds among the study population.

RESULTS

Fifty-four adult patients were included in the study. AKI was detected in 14 patients during polymyxin B treatment (25.9%, 14 out of 54). C_min (odds ratio [OR] 2.071; 95% confidence interval [CI] 1.235-3.472) and baseline serum creatinine (OR 1.024; 95% CI 1.005-1.043) were significant independent risk factors for developing AKI. The area under the ROC curve of the combined predictor was larger based on the above factors. When the Youden index was at maximum, the optimal cut-off point was 6.678 of the ROC curve. When C_min  ≥ 3.13 mg/L, the probability of AKI was more than 50%.

CONCLUSION

In this study, when the calculated combined predictor value was >6.678, there was an increased risk of AKI. Maintaining a polymyxin B C_min level below 3.13 mg/L may be helpful in reducing the incidence of polymyxin B associated nephrotoxicity.

Clinical use of intravenous polymyxin B for the treatment of patients with multidrug-resistant Gram-negative bacterial infections: An evaluation of the current evidence

OBJECTIVES

The epidemic dimensions of the emergence of multidrug-resistant (MDR) Gram-negative bacterial infections have led to the revival of old antibiotics, including the polymyxins.

METHODS

We performed a review and meta-analysis to evaluate the current literature data regarding the effectiveness and safety of intravenous polymyxin B in patients with MDR Gram-negative bacterial infections and the overall mortality and nephrotoxicity in patients treated with intravenous polymyxin B either as monotherapy or combination therapy.

RESULTS

A total of 5 prospective and 28 retrospective studies, 1 cross-sectional study, 2 retrospective case series and 7 case reports provided data regarding the effectiveness and/or toxicity of intravenous polymyxin B. All-cause mortality of 2910 patients (from 27 studies) who received intravenous polymyxin B was 41.2% (95% CI 35.5-47.0%). All-cause nephrotoxicity of 2994 patients (from 28 studies) treated with intravenous polymyxin B was 40.7% (95% CI 35.0-46.6%). Renal failure among 2111 patients (from 14 studies) was 11.2% (95% CI 8.7-13.9%).

CONCLUSION

Mortality of patients treated with intravenous polymyxin B is similar to the literature-reported mortality of patients treated with intravenous colistin, while nephrotoxicity associated with polymyxin B use is possibly milder compared with colistin use based on literature data. Head-to-head prospective studies would help to clarify the benefit of polymyxin B over colistin. However, a critical evaluation of the existing worldwide literature data supports the need for availability of the intravenous formulation of polymyxin B as a potentially useful option for the treatment of patients with MDR and extensively drug-resistant (XDR) Gram-negative bacterial infections.

Incidence of Acute Kidney Injury in Intermittent Versus Continuous Infusion of Polymyxin B in Hospitalized Patients

Background: Studies evaluating the risk of developing acute kidney injury (AKI) with different dosing strategies of polymyxin B are limited. Objectives: To compare the incidence of AKI in patients treated with intermittent versus continuous polymyxin B therapy. Secondary objectives included time to onset of AKI, hospital length of stay (LOS), and all-cause hospital mortality. Variables associated with an increased risk of AKI were evaluated. Methods: A retrospective record review was conducted at a single center in Puerto Rico. Adult patients (≥18 years old) treated with polymyxin B (first course) for at least 48 hours from 2013-2015 were evaluated. Patients with a creatinine clearance <10 mL/min and/or on renal replacement were excluded. Results: A total of 69 patients were included: 42 in the continuous infusion and 27 in the intermittent dosing group. Incidence of AKI was not significantly different between the groups (intermittent 41% vs continuous 31%, P = 0.4). No difference was found in the onset of nephrotoxicity, hospital LOS, or all-cause hospital mortality. Variables associated with increased risk of AKI were baseline serum creatinine, age, and intensive care unit admission. Patients with a body mass index (BMI) >25 kg/m² on polymyxin B via continuous infusion had a significantly higher cumulative incidence of AKI (P = 0.016). Conclusion and Relevance: No difference in the risk of polymyxin B nephrotoxicity was found between intermittent and continuous infusion administration. Administration of polymyxin B via a continuous infusion may result in a higher risk of AKI in patients with a BMI >25 kg/m².

A Comparison of Adjusted Versus Unadjusted Doses of Polymyxin B Based on Renal Function and Incidence of Acute Kidney Injury

Purpose:

To determine whether or not polymyxin B needs dose adjustments based on renal function by comparing the incidence of acute kidney injury (AKI) in patients whose polymyxin B doses were adjusted versus not adjusted according to renal function.

Methods:

This was a single-center, prospective study with a retrospective cohort taking place in an acute care community hospital. Forty-two patients treated with polymyxin B were evaluated between April 2012 and December 2015. The primary outcome was incidence of AKI at day 7 after initiation of polymyxin B therapy with secondary outcomes including microbiological cure, clinical cure, and 30-day mortality.

Results:

There was no difference in the incidence of AKI at day 7 in patients with polymyxin B doses adjusted according to renal function versus patients without polymyxin B dose adjustment (20.0% vs 18.2%; P = .882). There were no differences between groups in occurrence of microbiological cure, clinical cure, or 30-day mortality (27.8% vs 57.1%; P = .065, 70.0% vs 72.7%; P = .845, 40.0% vs 31.8%; P = .581, respectively).

Conclusion:

The results from this study support the use of polymyxin B without any dose adjustment in the setting of renal impairment.

Nephrotoxicity Associated with Intravenous Polymyxin B Once- versus Twice-Daily Dosing Regimen

Nephrotoxicity is a known adverse effect of polymyxin B (PMB). Animal data suggest that once-daily dosing may reduce the rate and delay the onset of acute kidney injury (AKI). In a multicenter retrospective study, we evaluated adult patients with a creatinine clearance (CrCl) of ≥30 ml/min who received ≥48 h of PMB therapy. The primary endpoint was the difference in rate of AKI comparing once- and twice-daily PMB dosing. The secondary endpoints included the time to AKI and the recovery of renal function. Of 273 eligible patients, 100 from each group were matched on the basis of propensity scores. In the matched groups, nephrotoxicity, defined according to risk, injury, failure, loss, and end-stage renal disease (RIFLE) criteria, was more frequent with once- than with twice-daily dosing (47% versus 17%, respectively; P = 0.0005). After adjusting for residual differences by multivariate conditional logistic regression, once-daily dosing was more likely to result in nephrotoxicity (adjusted odds ratio, 2.5; 95% confidence interval [CI], 1.413 to 4.541; P = 0.002). Among 64 patients who developed AKI, the median onsets were similar between the groups (7 days with once versus 6 days with twice-daily dosing, P = 0.095). Of 37 patients who had their serum creatinine evaluated subsequently, 29/37 (78%) had recovery of renal function. No patient required renal replacement therapy. Our findings suggest that AKI is significantly more common with PMB once daily than with twice-daily dosing with no difference in time to AKI. A prospective randomized study is warranted to validate these results.

Personalizing Polymyxin B Dosing Using an Adaptive Feedback Control Algorithm

Polymyxin B is used as an antibiotic of last resort for patients with multidrug-resistant Gram-negative bacterial infections; however, it carries a significant risk of nephrotoxicity. Herein we present a polymyxin B therapeutic window based on target area under the concentration-time curve (AUC) values and an adaptive feedback control algorithm (algorithm) which allows for the personalization of polymyxin B dosing. The upper bound of this therapeutic window was determined through a pharmacometric meta-analysis of polymyxin B nephrotoxicity data, and the lower bound was derived from murine thigh infection pharmacokinetic (PK)/pharmacodynamic (PD) studies. A previously developed polymyxin B population pharmacokinetic model was used as the backbone for the algorithm. Monte Carlo simulations (MCS) were performed to evaluate the performance of the algorithm using different sparse PK sampling strategies. The results of the nephrotoxicity meta-analysis showed that nephrotoxicity rate was significantly correlated with polymyxin B exposure. Based on this analysis and previously reported murine PK/PD studies, the target AUC_0–24 (AUC from 0 to 24 h) window was determined to be 50 to 100 mg · h/liter. MCS showed that with standard polymyxin B dosing without adaptive feedback control, only 71% of simulated subjects achieved AUC values within this window. Using a single PK sample collected at 24 h and the algorithm, personalized dosing regimens could be computed, which resulted in >95% of simulated subjects achieving AUC_0–24 values within the target window. Target attainment further increased when more samples were used. Our algorithm increases the probability of target attainment by using as few as one pharmacokinetic sample and enables precise, personalized dosing in a vulnerable patient population.

The safety of polymyxin antibiotics

INTRODUCTION

The emergence of multidrug-resistant gram-negative bacteria has led to the increasing use of polymyxins. Nephrotoxicity and, to a lesser degree, neurotoxicity occur often during systemic polymyxin therapy. Scientific evidence regarding safety associated with polymyxins remains limited.

AREAS COVERED

Case reports/case series, observational studies and clinical trials assessing safety and toxicity of polymyxins were critically reviewed.

EXPERT OPINION

Polymyxins are drugs with a narrow therapeutic range. Nephrotoxicity is associated with both host factors and polymyxin exposure, and recent studies suggest that the relative risk of nephrotoxicity is similar for colistin and polymyxin B. Studies that have examined the safety of polymyxins have several limitations. Considering the available evidence, toxicities that may develop while on polymyxin therapy most often are mild to moderate in magnitude and reversible in nature. Strategies to minimize toxicity associated with polymyxins have evolved and include avoidance of toxic medications, careful dosing, use of critical care, therapeutic drug monitoring and development of polymyxin derivatives. However, given that polymyxin use has re-emerged in an era of increased antimicrobial resistance, the presence of other treatment modalities may be limited. Therefore, clinicians must consider overall risk to benefit ratio of continuing versus stopping polymyxin treatment and optimize minimization strategies to reduce polymyxin-induced toxicities.

Risk factors for nephrotoxicity onset associated with polymyxin B therapy

OBJECTIVES

Polymyxin B is an active agent against many MDR Gram-negative bacteria, but nephrotoxicity is a major hindrance to its widespread use. To guide its optimal use, we determined the risk factors for nephrotoxicity onset associated with polymyxin B.

METHODS

In a multicentre, retrospective, cohort study, we evaluated adult patients with normal renal function who received ≥72 h of polymyxin B therapy. Pertinent information was retrieved from medical records; patients were followed for up to 30 days after therapy was started. The primary endpoint of this study was the onset of nephrotoxicity. A Cox proportional hazards model was used for analysis.

RESULTS

A total of 192 patients (52.1% male, 67.7% Caucasian) were evaluated. The mean ± SD age, actual body weight (ABW) and daily dose by ABW were 68.3 ± 17.2 years, 71.5 ± 20.4 kg and 1.5 ± 0.5 mg/kg, respectively. The median duration of therapy was 9.5 days. The overall prevalence rate of nephrotoxicity was 45.8% and the median onset of nephrotoxicity was 9 days. Independent risk factors for the onset of nephrotoxicity included daily dose by ABW (HR = 1.73; P = 0.022), concurrent use of vancomycin (HR = 1.89; P = 0.005) and contrast media (HR = 1.79; P = 0.009). Nephrotoxicity was seen earlier in the high-risk group (P = 0.003).

CONCLUSIONS

Risk factors for nephrotoxicity onset associated with polymyxin B were identified. In conjunction with susceptibility and other pharmacokinetic/pharmacodynamic data, our results can be used to optimize treatment for MDR Gram-negative infections.

Risk factors for treatment failure of polymyxin B monotherapy for carbapenem-resistant Klebsiella pneumoniae infections

Polymyxins are reserved for salvage therapy of infections caused by carbapenem-resistant Klebsiella pneumoniae (CRKP). Though synergy has been demonstrated for the combination of polymyxins with carbapenems or tigecycline, in vitro synergy tests are nonstandardized, and the clinical effect of synergy remains unclear. This study describes outcomes for patients with CRKP infections who were treated with polymyxin B monotherapy. We retrospectively reviewed the medical records of patients with CRKP infections who received polymyxin B monotherapy from 2007 to 2011. Clinical, microbiology, and antimicrobial treatment data were collected. Risk factors for treatment failure were identified by logistic regression. Forty patients were included in the analysis. Twenty-nine of 40 (73%) patients achieved clinical cure as defined by clinician-documented improvement in signs and symptoms of infections, and 17/32 (53%) patients with follow-up culture data achieved microbiological cure. End-of-treatment mortality was 10%, and 30-day mortality was 28%. In a multivariate analysis, baseline renal insufficiency was associated with a 6.0-fold increase in clinical failure after adjusting for septic shock (odds ratio [OR] = 6.0; 95% confidence interval [CI] = 1.22 to 29.59). Breakthrough infections with organisms intrinsically resistant to polymyxins occurred in 3 patients during the treatment. Eighteen of 40 (45%) patients developed a new CRKP infection a median of 23 days after initial polymyxin B treatment, and 3 of these 18 infections were polymyxin resistant. The clinical cure rate achieved in this retrospective study was 73% of patients with CRKP infections treated with polymyxin B monotherapy. Baseline renal insufficiency was a risk factor for treatment failure after adjusting for septic shock. Breakthrough infections with organisms intrinsically resistant to polymyxin B and development of resistance to polymyxin B in subsequent CRKP isolates are of concern.

Higher incidence of acute kidney injury with intravenous colistimethate sodium compared with polymyxin B in critically ill patients at a tertiary care medical center

Nephrotoxicity was assessed in 173 critically ill patients receiving intravenous colistin or polymyxin B; it occurred in 60.4% and 41.8%, respectively. Further investigation is necessary to elucidate the reason for the difference in nephrotoxicity observed between the groups and to assess the impact of severity of illness and dosing/administration.