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Colistimethate sodium (CMS) is widely administrated for the treatment of life-threatening infections caused by multidrug-resistant Gram-negative bacteria. Until now, the quality control of CMS formulations has been based on microbiological assays. Herein, an ultra-high-performance liquid chromatography coupled to ultraviolet detector methodology was developed for the quantitation of CMS in injectable formulations. The design of experiments was performed for the optimization of the chromatographic parameters. The chromatographic separation was achieved using a Waters Acquity BEH C 8 column employing gradient elution with a mobile phase consisting of (A) 0.001 M aq. ammonium formate and (B) methanol/acetonitrile 79/21 ( v / v ). CMS compounds were detected at 214 nm. In all, 23 univariate linear-regression models were constructed to measure CMS compounds separately, and one partial least-square regression (PLSr) model constructed to assess the total CMS amount in formulations. The method was validated over the range 100-220 μg mL -1 . The developed methodology was employed to analyze several batches of CMS injectable formulations that were also compared against a reference batch employing a Principal Component Analysis, similarity and distance measures, heatmaps and the structural similarity index. The methodology was based on freely available software in order to be readily available for the pharmaceutical industry.

Colistimethate (CMS), the prodrug of polymyxin E (colistin), is an antibiotic widely used as a last-line therapy against multidrug resistant Gram-negative bacteria, but little is known about its pharmacokinetics as its administration has stopped as a result of high neuro- and nephro-toxicity. The measurement of CMS levels in patients' biological fluids is of great importance in order to find the optimal dose regimen reducing the drug toxicity. Until now, CMS assay methods are based on the indirect determination after its hydrolysis to colistin (CS). Herein, the aim is to find the optimal conditions for the complete hydrolysis of CMS to CS. The reaction was studied at accelerated conditions: 40 °C, 50 °C, and 60 °C, and the results were evaluated by assessing the Arrhenius equation and computation employing the Tenua software. A validated analytical methodology based on ultra-performance liquid chromatography (UPLC) coupled to a hybrid quadrupole time of flight (QToF) instrument is developed for the simultaneous measurement of CMS and CS. The current methodology resulted in complete hydrolysis, in contrast with the previously reported one.

Objectives: The aim of this study was to assess colistin use in a country endemic for multidrug-resistant Gram-negative bacteria (MDR-GNB)., Methods: Colistin prescription patterns were evaluated in 22 Italian centres. Factors associated with use of colistin in combination with other anti-MDR-GNB agents were also assessed., Results: A total of 221 adults receiving colistin were included in the study. Their median age was 64 years (interquartile range 52-73 years) and 134 (61%) were male. Colistin was mostly administered intravenously (203/221; 92%) and mainly for targeted therapy (168/221; 76%). The most frequent indications for colistin therapy were bloodstream infection and lower respiratory tract infection. Intravenous colistin was administered in combination with at least another anti-MDR-GNB agent in 80% of cases (163/203). A loading dose of 9 MU of colistimethate was administered in 79% of patients receiving i.v. colistin and adequate maintenance doses in 85%. In multivariable analysis, empirical therapy [odds ratio (OR) = 3.25, 95% confidence interval (CI) 1.24-8.53;P = 0.017] and targeted therapy for carbapenem-resistant Enterobacterales infection (OR = 4.76, 95% CI 1.69-13.43; P = 0.003) were associated with use of colistin in combination with other agents, whilst chronic renal failure (OR = 0.39, 95% CI 0.17-0.88; P =  0.024) was associated with use of colistin monotherapy., Conclusion: Colistin remains an important option for severe MDR-GNB infections when other treatments are not available. Despite inherent difficulties in optimising its use owing to peculiar pharmacokinetic/pharmacodynamic characteristics, colistin was mostly used appropriately in a country endemic for MDR-GNB., (Copyright © 2019 International Society for Antimicrobial Chemotherapy. Published by Elsevier Ltd. All rights reserved.)

Starting from a warning of possible artificially high plasma colistin concentrations observed in clinical samples in our recently published LC-MS/MS method, we reviewed our analytical assay and demonstrated, for the first time, that caution must be paid to ionization conditions employed in the MS system. The artefact reported here demonstrates that additional experiments should be performed in the course of validation of LC-MS/MS methods to be used in samples containing both colistin and colistimethate., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Nephrotoxicity is a common adverse effect of the clinically used polymyxins, colistin and polymyxin B. This adverse effect is dose limiting for both polymyxins, as the plasma polymyxin concentrations associated with renal damage overlap those required for antibacterial effect. Since development of acute kidney injury (AKI) during therapy is highly undesirable, it is extremely important to know whether there is any difference between the nephrotoxic potential of colistin (administered as its inefficient prodrug, colistimethate) and polymyxin B (administered as the active form). Both polymyxins are cytotoxic to renal tubular cells and are prone to cause nephrotoxicity in vivo because of the renal handling mechanisms that facilitate accumulation of these compounds in these cells, processes that are reviewed in this article. Also reviewed are the emerging data that strongly suggest significantly higher rates of AKI in patients treated with colistimethate compared to patients treated with polymyxin B. This finding may be due to differences in pharmacokinetics and renal handling mechanisms of colistimethate and formed colistin versus polymyxin B, and consequently the relative amount of polymyxin material delivered to tubular cells. A lower risk of AKI with polymyxin B is one of several potential advantages over colistimethate. The relative safety and efficacy of the two agents require closer examination in well-designed clinical studies., (Copyright © 2017 American Society for Microbiology.)

We report the case of a patient with a history of chronic bronchiectasis that presented with new onset fatigue, shortness of breath, peripheral blood eosinophilia and infiltrates on chest radiograph. Eight days previously, she was prescribed inhaled colistimethate sodium 75 mg bid to prevent exacerbations of her respiratory condition. To our knowledge, our case is the first to show the clinical and radiologic features of inhaled-colistimethate-induced pulmonary eosinophilia. It also shows the rapid resolution of its features following treatment with oral corticosteroids. Eosinophilic lung reaction to inhaled colistin is rarely reported in the literature. Clinicians should be aware of this possible side effect., (Copyright © 2016 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.)

Colistin (polymyxin E) is a mainly concentration-dependent bactericidal antimicrobial active against multidrug-resistant Gram-negative bacteria. After being abandoned over the past 30 years due to its neuro- and nephrotoxicity, colistin has been reintroduced recently as a last-resort drug for the treatment of multidrug-resistant Gram-negative bacteria infections in combination with other antimicrobials. Unfortunately, although renal toxicity is a well-known dose-related adverse effect of colistin, relatively few studies are currently available on its peculiar pharmacodynamic/pharmacokinetic properties in clinical settings at high risk for drug accumulation, such as acute or chronic kidney disease. In these specific contexts, the risk for underdosing is also substantial because colistin can be easily removed by dialysis/hemofiltration, especially when the most efficient modalities of renal replacement therapy (RRT) are used in critically ill patients. For this reason, recent recommendations in patients undergoing RRT have shifted toward higher dosing regimens, and therapeutic drug monitoring is advised. This review aims to summarize the main issues related to chemical structure, pharmacodynamics/pharmacokinetics, and renal toxicity of colistin. Moreover, recent data and current recommendations concerning colistin dosing in patients with reduced kidney function, with special regard to those receiving RRT such as dialysis or hemofiltration, are also discussed., (Copyright © 2016 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.)

Colistin has re-emerged as an essential antibiotic for the treatment of carbapenem-resistant Gram-negative infections. Unfortunately, its utility is limited by high rates of nephrotoxicity, even at potentially therapeutic concentrations, and an overall lack of understanding on how to optimally administer the agent. In this review, recent advancements in the understanding of the safety and efficacy of colistin are discussed and strategies and suggestions on how to balance the two are described.

Colistin, the most widely used polymyxin antibiotic, was originally introduced in the late 1950s before the establishment of the present-day drug approval process. Originally shelved due to toxicity concerns, colistin, in the form of its inactive prodrug colistin methanesulfonate, has undergone a renaissance in the past 15 years. Unfortunately, this is not because of an improved adverse-effect profile but because colistin is among the only remaining antibiotics with activity against multidrug-resistant gram-negative bacilli. Pharmacokinetic and pharmacodynamic data are limited to guide the appropriate use of colistin; however, important advances have occurred over the past 5 years. Since its reintroduction, published reports regarding colistin have produced discordant results in terms of both efficacy and safety. Because the efficacy and toxicity of colistin are dose dependent, the impact of discordant dosing recommendations cannot be understated. This review highlights the issues leading to differing and often conflicting dosing recommendations, reviews the recent pharmacokinetic advances, and provides recommendations for the optimal use of colistin., (© 2014 Pharmacotherapy Publications, Inc.)

This article reviews mechanisms, incidences, risk factors and preventive modalities of colistin toxicity as well as colistin use in special populations and through special routes. All clinical studies that examined the pharmacokinetic/pharmacodynamic, efficacy and side effects of colistin in the management of multidrug-resistant organisms in different patient population including pediatrics, adults, obese, critically ill, burn or cancer patients with any route of drug administration were considered. Compared with older recommended doses, current dosing approach improves cure rate without significant increase in the rate of colistin-induced nephrotoxicity. Efficacy and safety of high doses of colistin should be considered in the future studies. Also comparing efficacy and safety of different doses of aerosolized colistin and defining the appropriate dose in different populations is another open area of future researches.

With the reintroduction of colistimethate and polymyxin B into clinical practice, a review of their individual and comparative nephrotoxicity attributes as reported in contemporary literature was undertaken. Given variability in definitions used for acute kidney injury, a particular focus was placed on studies utilizing the Risk-Injury-Failure-Loss-End Stage Kidney Disease (RIFLE) criteria of assessment to provide for standardized comparison. Primary risk factors examined included the influence of dosing and the receipt of concomitant nephrotoxins. The typical severity and time course of renal injury that develops were also analyzed. Nephrotoxicity rates with colistimethate appear to approach 50%, and could be of lower frequency and severity with polymyxin B based on limited literature. Acute kidney injury generally appears to be mild to moderate in magnitude and reversible in nature, though as many as 20% of patients experiencing it may require renal replacement therapy of some duration. The majority of studies showed some relationship with dosing- variably reported as being associated with daily dose or cumulative exposure. Traditional nephrotoxic agents did not appear to confer additional risk individually in the majority of investigations, though receipt of multiple concurrent nephrotoxins did yield a relationship in several. Further studies will be required to better characterize the renal adverse effect profile of these agents, particularly in the case of polymyxin B., (© The Author(s) 2014.)

Background: Colistin, administered as intravenous colistimethate (CMS), is still used in the critical care setting and current guidelines recommend high dosage CMS in patients undergoing continuous renal replacement therapy (CRRT). Due to the paucity of real-life data, we aimed to describe colistin pharmacokinetic/pharmacodynamic (PK/PD) profile in a cohort of critically ill patients with infections due to carbapenem-resistant (CR) bacteria undergoing CRRT. Results: All consecutive patients admitted to three Intensive Care Units (ICUs) of a large metropolitan University Hospital, treated with colistin for at least 48 h at the dosage of 6.75 MUI q12, after 9 MIU loading dose, and undergoing CRRT were included. After the seventh dose, patients underwent blood serial sampling during a time frame of 24 h. We included 20 patients, who had CR-Acinetobacter baumannii ventilator-associated pneumonia and were characterized by a median SAPS II and SOFA score of 41 [34.5–59.3] and 9 [6.7–11], respectively. Fifteen patients died during ICU stay and six recovered renal function. Median peak and trough colistin concentrations were 16.6 mcg/mL [14.8–20.6] and 3.9 mcg/mL [3.3–4.4], respectively. Median area under the time–concentration curve (AUC0 − 24) and average steady-state concentration (Css, avg) were 193.9 mcg h/mL [170.6–208.6] and 8.07 mcg/mL [7.1–8.7]. Probability of target attainment of colistin pharmacodynamics according to the fAUC0 − 24/MIC target ≥ 12 was 100% for MIC ≤ 2 mcg/mL and 85% for MIC = 4 mcg/ML, although exceeding the toxicity limit of Css, avg 3–4 mcg/mL. Conclusions: In critically ill patients with CR infections undergoing CRRT, recommended CMS dosage resulted in colistin plasmatic levels above bacterial MIC90, but exceeding the safety Css, avg. limit. Trial registration: This trial was registered in ClinicalTrials.gov on 23/07/2021 with the ID NCT04995133 (https//clinicaltrials.gov/study/NCT04995133). [ABSTRACT FROM AUTHOR]

Abstract Background Colistin, administered as intravenous colistimethate (CMS), is still used in the critical care setting and current guidelines recommend high dosage CMS in patients undergoing continuous renal replacement therapy (CRRT). Due to the paucity of real-life data, we aimed to describe colistin pharmacokinetic/pharmacodynamic (PK/PD) profile in a cohort of critically ill patients with infections due to carbapenem-resistant (CR) bacteria undergoing CRRT. Results All consecutive patients admitted to three Intensive Care Units (ICUs) of a large metropolitan University Hospital, treated with colistin for at least 48 h at the dosage of 6.75 MUI q12, after 9 MIU loading dose, and undergoing CRRT were included. After the seventh dose, patients underwent blood serial sampling during a time frame of 24 h. We included 20 patients, who had CR-Acinetobacter baumannii ventilator-associated pneumonia and were characterized by a median SAPS II and SOFA score of 41 [34.5–59.3] and 9 [6.7–11], respectively. Fifteen patients died during ICU stay and six recovered renal function. Median peak and trough colistin concentrations were 16.6 mcg/mL [14.8–20.6] and 3.9 mcg/mL [3.3–4.4], respectively. Median area under the time–concentration curve (AUC0 − 24) and average steady-state concentration (Css, avg) were 193.9 mcg h/mL [170.6–208.6] and 8.07 mcg/mL [7.1–8.7]. Probability of target attainment of colistin pharmacodynamics according to the fAUC0 − 24/MIC target ≥ 12 was 100% for MIC ≤ 2 mcg/mL and 85% for MIC = 4 mcg/ML, although exceeding the toxicity limit of Css, avg 3–4 mcg/mL. Conclusions In critically ill patients with CR infections undergoing CRRT, recommended CMS dosage resulted in colistin plasmatic levels above bacterial MIC90, but exceeding the safety Css, avg. limit. Trial registration This trial was registered in ClinicalTrials.gov on 23/07/2021 with the ID NCT04995133 (https//clinicaltrials.gov/study/NCT04995133).

Victor Hugo Ahumada Topete,1,* Kevin Jesus de Dios Sanchez,1,* Gustavo Alejandro Casas Aparicio,2 Graciela Hernandez Silva,2 Cesar Emmanuel Lopez Vejar,1 Luz Maria Torres Espíndola,3 Arnoldo Aquino-Galvez,4 Odalis Rodriguez Ganen,5 Manuel de Jesus Castillejos Lopez1 1Hospital Epidemiology and Infectology Unit, National Institute of Respiratory Diseases Ismael Cosío Villegas, Mexico City, Mexico; 2Department of Infectious Disease Research, National Institute of Respiratory Diseases Ismael Cosío Villegas, Mexico City, Mexico; 3Laboratory of Pharmacology, National Institute of Pediatrics, Mexico City, Mexico; 4Molecular Biology Laboratory, National Institute of Respiratory Diseases Ismael Cosío Villegas, Mexico City, Mexico; 5Department of Hospital Pharmacy, National Institute of Respiratory Diseases Ismael Cosío Villegas, Mexico City, Mexico*These authors contributed equally to this workCorrespondence: Manuel de Jesus Castillejos Lopez; Arnoldo Aquino Galvez, Email mcastillejos@gmail.com; araquiga@yahoo.comAbstract: The adverse events related to sodium colistimethate have had variability regarding the prevalence of nephrotoxicity, neurotoxicity, and less frequent respiratory depression. In recent years, its use has been relevant due to the increase of multidrug-resistant bacteria since it is considered the last-line drug, being its main adverse event and reason for discrepancies between authors’ nephrotoxicity. The indiscriminate use of antibiotic therapy has generated multiple mechanisms of resistance, the most common being related to Colistin, the bactericidal escape effect. Based on the search criteria, no randomized clinical trials were identified showing safety and efficacy with the use of Colistin, inferring that the application of the appropriate dose is governed by expert opinion and retrospective and prospective observational studies, which confounding factors such as the severity of the patient and the predisposition to develop acute renal failure are constant. In this review, we focus on identifying the mechanism of nephrotoxicity and bacterial resistance, where much remains to be known.Keywords: colistin, colistimethate, nephrotoxicity, neurotoxicity, resistance mechanism, multidrug-resistant gram-negative bacteria, risk factors, high doses, toxicity

The adverse events related to sodium colistimethate have had variability regarding the prevalence of nephrotoxicity, neurotoxicity, and less frequent respiratory depression. In recent years, its use has been relevant due to the increase of multidrug-resistant bacteria since it is considered the last-line drug, being its main adverse event and reason for discrepancies between authors' nephrotoxicity. The indiscriminate use of antibiotic therapy has generated multiple mechanisms of resistance, the most common being related to Colistin, the bactericidal escape effect. Based on the search criteria, no randomized clinical trials were identified showing safety and efficacy with the use of Colistin, inferring that the application of the appropriate dose is governed by expert opinion and retrospective and prospective observational studies, which confounding factors such as the severity of the patient and the predisposition to develop acute renal failure are constant. In this review, we focus on identifying the mechanism of nephrotoxicity and bacterial resistance, where much remains to be known. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to assess colistin use in a country endemic for multidrug-resistant Gram-negative bacteria (MDR-GNB). Methods: Colistin prescription patterns were evaluated in 22 Italian centres. Factors associated with use of colistin in combination with other anti-MDR-GNB agents were also assessed. Results: A total of 221 adults receiving colistin were included in the study. Their median age was 64 years (interquartile range 52–73 years) and 134 (61%) were male. Colistin was mostly administered intravenously (203/221; 92%) and mainly for targeted therapy (168/221; 76%). The most frequent indications for colistin therapy were bloodstream infection and lower respiratory tract infection. Intravenous colistin was administered in combination with at least another anti-MDR-GNB agent in 80% of cases (163/203). A loading dose of 9 MU of colistimethate was administered in 79% of patients receiving i.v. colistin and adequate maintenance doses in 85%. In multivariable analysis, empirical therapy [odds ratio (OR) = 3.25, 95% confidence interval (CI) 1.24–8.53;P = 0.017] and targeted therapy for carbapenem-resistant Enterobacterales infection (OR = 4.76, 95% CI 1.69–13.43; P = 0.003) were associated with use of colistin in combination with other agents, whilst chronic renal failure (OR = 0.39, 95% CI 0.17–0.88; P = 0.024) was associated with use of colistin monotherapy. Conclusion: Colistin remains an important option for severe MDR-GNB infections when other treatments are not available. Despite inherent difficulties in optimising its use owing to peculiar pharmacokinetic/pharmacodynamic characteristics, colistin was mostly used appropriately in a country endemic for MDR-GNB.

Background: Acinetobacter baumannii has been recognized as a cause of nosocomial infection. To date, polymyxins, the last-resort therapeutic agents for carbapenem-resistant A. baumannii (CRAB). Thus, the small number of effective antibiotic options against CRAB represents a challenge to human health. This study examined the appropriate dosage regimens of colistin alone or in combination with sulbactam or fosfomycin using Monte Carlo simulation with the aims of improving efficacy and reducing the risk of nephrotoxicity. Materials and Methods: Clinical CRAB isolates were obtained from patients admitted to Phramongkutklao Hospital in 2014 and 2015. The minimum inhibitory concentration (MIC) of colistin for each CRAB isolate was determined using the broth dilution method, whereas those of sulbactam and fosfomycin were determined using the agar dilution method. Each drug regimen was simulated using the Monte Carlo technique to calculate the probability of target attainment (PTA) and the cumulative fraction of response (CFR). Nephrotoxicity based on RIFLE (Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease) criteria was indicated by colistin trough concentration exceeding ≥3.3 µg/mL. Results: A total of 50 CRAB isolates were included. The MIC50 and MIC90 were 64 and 128 µg/mL, respectively, for sulbactam, 256 and 2,048 µg/mL, respectively, for fosfomycin, and 1 and 4 µg/mL, respectively, for colistin. In patients with creatinine clearance of 91 – 130 m/min, the dosing regimens of 180 mg every 12 h and 150 mg every 8 h achieved ≥ 90% of target of the area under the free drug plasma concentration–time curve from 0 to 24 hr (fAUC24)/MIC ≥25 against isolates MICs of ≤0.25 and ≤0.5 µg/mL, respectively, and their rates of colistin trough concentration more than ≥3.3 µg/mL were 35 and 54%, respectively. Colistin combined with sulbactam or fosfomycin decreased the colistin MIC of CRAB isolates from 1 – 16 µg/mL to 0.0625 – 1 and 0.0625 – 2 µg/mL, respectively. Based on CFR ≥ 90%, no colistin monotherapy regimens in patients with creatinine clearance of 91 – 130 mL/min were effective against all of the studied CRAB isolates. For improving efficacy and reducing the risk of nephrotoxicity, colistin 150 mg given every 12 h together with sulbactam (≥6 g/day) or fosfomycin (≥18 g/day) was effective in patients with creatinine clearance of 91 – 130 mL/min. Additionally, both colistin combination regimens were effective against five colistin-resistant A. baumannii isolates. Conclusion: Colistin monotherapy at the maximum recommended dose might not cover some CRAB isolates. Colistin combination therapy appears appropriate for achieving the pharmacokinetic/pharmacodynamic targets of CRAB treatment. [ABSTRACT FROM AUTHOR]

Background Nephrotoxicity is a known adverse effect of polymyxin antibiotics, including colistin. Although previous meta-analyses have aimed to characterize colistin-associated nephrotoxicity risk relative to other antibiotics, included studies were observational in nature with high risk of confounding and heterogeneity. We conducted this systematic review and meta-analysis of exclusively randomized controlled trials (RCTs) to evaluate the incidence of nephrotoxicity associated with colistin versus minimally nephrotoxic antibiotics. Methods We searched PubMed, EMBASE, Cochrane Library, and 3 trial registries for RCTs comparing the nephrotoxicity of colistin to nonpolymyxin antibiotics. Randomized controlled trials that used aminoglycosides were excluded. Risk ratios (RRs) and 95% confidence intervals (CIs) were calculated using random-effects models. The study outcome was the rate of nephrotoxicity. Results Five RCTs with a total of 377 patients were included. Most patients received colistin for pneumonia in the intensive care unit, and the comparators were β-lactam-based regimens. Colistimethate sodium was dosed at 9 million units/day (300 mg/day of colistin base activity), with administration of a loading dose in 4 studies. The nephrotoxicity incidence in patients who received colistin was 36.2% (95% CI, 23.3% to 51.3%). The nephrotoxicity rate was significantly higher in the colistin arm than comparators (RR, 2.40; 95% CI, 1.47 to 3.91; P ≤.001; I2 = 0%), and the number needed to harm was 5. Findings persisted upon one-study-removed-analysis. Conclusions This meta-analysis of RCTs found a colistin-associated nephrotoxicity rate of 36.2% and an increase in this risk compared with β-lactam-based regimens by 140%. Colistin should be regarded as a last-line agent and safer alternatives should be considered when possible. [ABSTRACT FROM AUTHOR]

Objectives: To assess the pharmacokinetics of formed colistin in plasma and the safety of two different high doses of colistimethate sodium administered via nebulization in critically ill surgical patients with hospital-acquired pneumonia (HAP) or ventilator-associated pneumonia (VAP).Patients and Methods: Formed colistin plasma concentrations were measured in critically ill surgical patients with pneumonia treated with two different doses of nebulized colistimethate sodium (3 MIU/8 h versus 5 MIU/8 h). Adverse events possibly related to nebulized colistimethate sodium were recorded.Results: Twenty-seven patients (15 in the 3 MIU/8 h group and 12 in the 5 MIU/8 h group) were included. Colistin plasma concentrations were unquantifiable (<0.1 mg/L) in eight (53.3%) patients in the 3 MIU/8 h group and in seven patients (58.3%) in the 5 MIU/8 h group. Median (IQR) quantifiable colistin plasma concentrations before nebulization and at 1, 4 and 8 h were 0.17 (0.12-0.33), 0.20 (0.11-0.24), 0.17 (0.12-0.23) and 0.17 (0.11-0.32) mg/L, respectively, in the 3 MIU/8 h group and 0.20 (0.11-0.35), 0.24 (0.12-0.44), 0.24 (0.10-0.49) and 0.23 (0.11-0.44) mg/L, respectively, in the 5 MIU/8 h group, with no differences between the two groups at any time. Renal impairment during nebulized treatment was observed in three patients in each group, but was unlikely to be related to colistimethate sodium treatment. Nebulized colistimethate sodium therapy was well tolerated and no bronchospasms or neurotoxicity events were observed.Conclusions: In this limited observational case series of critically ill patients with HAP or VAP treated with high doses of nebulized colistimethate sodium, systemic exposure was minimal and the treatment was well tolerated. [ABSTRACT FROM AUTHOR]

Objectives: Nebulized colistimethate sodium (CMS) can be used to treat ventilator-associated pneumonia caused by MDR bacteria. The influence of the diluent volume of CMS on aerosol delivery has never been studied. The main objectives of the study were to compare aerosol particle characteristics and plasma and urine pharmacokinetics between two diluent volumes in patients treated with nebulized CMS.Methods: A crossover study was conducted in eight patients receiving nebulized CMS every 8 h. After inclusion, nebulization started with 4 million international units (MIU) of CMS diluted either in 6 mL (experimental dilution) or in 12 mL (recommended dilution) of normal saline in a random order. For each diluent volume, CMS aerosol particle sizes were measured and plasma and urine samples were collected every 2 h. Nebulization time and stability of colistin in normal saline were assessed.Results: The mass median aerodynamic diameters were 1.4 ± 0.2 versus 0.9 ± 0.2 μm (P < 0.001) for 6 and 12 mL diluent volumes, respectively. The plasma area under the concentration-time curve from 0 to 8 h (AUC0-8) of colistinA+B was 6.6 (4.3-17.0) versus 6.7 (3.6-14.0) μg·h/mL (P = 0.461) for each dilution. The total amount of colistin and CMS eliminated in the urine represented, respectively, 17% and 13% of the CMS initially placed in the nebulizer chamber for 6 and 12 mL diluent volumes (P = 0.4). Nebulization time was shorter [66 (58-75) versus 93 (69-136) min, P = 0.042] and colistin stability was better with the 6 mL diluent volume.Conclusions: Nebulization with a higher concentration of CMS in saline (4 MIU in 6 mL) decreases nebulization time and improves colistin stability without changing plasma and urine pharmacokinetics or aerosol particle characteristics for lung deposition. [ABSTRACT FROM AUTHOR]

The purpose was to evaluate the clinical outcome in multi-drug resistant Pseudomonas aeruginosa (MDR-PA) bacterial keratitis and report the successful use of an alternative antibiotic, topical colistimethate in some of them. The medical records of 12 culture-proven MDR-PA keratitis patients, all exhibiting in vitro resistance by Kirby-Bauer disc diffusion method to ≥ three classes of routinely used topical antibiotics were reviewed. Eight patients were treated with 0.3% ciprofloxacin or ofloxacin, 1 patient with 5% imipenem/cilastatin and 3 patients with 1.6% colistimethate. The outcomes in 8 eyes treated with only fluoroquinolones were evisceration in 4 eyes, therapeutic corneal graft in 1 eye, phthisis bulbi in 1 eye, and no improvement in 2 eyes. The eye treated with imipenem/cilastin required a therapeutic corneal graft. All the three eyes treated with 1.6% colistimethate healed. Colistimethate may prove to be an effective alternative antibiotic in the treatment of MDR-PA keratitis. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa is the major pathogenic bacteria in cystic fibrosis and other forms of bronchiectasis. Growth in antibiotic-resistant biofilms contributes to the virulence of this organism. Sodium nitrite has antimicrobial properties and has been tolerated as a nebulized compound at high concentrations in human subjects with pulmonary hypertension; however, its effects have not been evaluated on biotic biofilms or in combination with other clinically useful antibiotics. We grew P. aeruginosa on the apical surface of primary human airway epithelial cells to test the efficacy of sodium nitrite against biotic biofilms. Nitrite alone prevented 99% of biofilm growth. We then identified significant cooperative interactions between nitrite and polymyxins. For P. aeruginosa growing on primary CF airway cells, combining nitrite and colistimethate resulted in an additional log of bacterial inhibition compared to treating with either agent alone. Nitrite and colistimethate additively inhibited oxygen consumption by P. aeruginosa. Surprisingly, whereas the antimicrobial effects of nitrite in planktonic, aerated cultures are nitric oxide (NO) dependent, antimicrobial effects under other growth conditions are not. The inhibitory effect of nitrite on bacterial oxygen consumption and biofilm growth did not require NO as an intermediate as chemically scavenging NO did not block growth inhibition. These data suggest an NO-radical independent nitrosative or oxidative inhibition of respiration. The combination of nebulized sodium nitrite and colistimethate may provide a novel therapy for chronic P. aeruginosa airway infections, because sodium nitrite, unlike other antibiotic respiratory chain “poisons,” can be safely nebulized at high concentration in humans. [ABSTRACT FROM AUTHOR]

Evaluation of: Colistin and Rifampicin compared with colistin alone for the treatment of serious infections due to extensively drug-resistant Acinetobacter baumannii: a multicenter, randomized, clinical trial. Clin. Infect. Dis. 57(3), 349-358 (2013). Despite many theoretical and in vitro advantages, clinical data comparing combination therapy with colistin + rifampicin to colistin alone for infection due to extremely-drug resistant (XDR) Acinetobacter baumanni are scarce and limited by small numbers and/or low quality evidence. This article represents the first large, randomized, controlled, prospective study comparing colistin monotherapy and combination therapy. The reviewed article found no difference in all cause or infection related mortality, though there was an improved rate of microbiological clearance in the combination therapy arm. This study adds important new data to the literature and sets the stage for future studies that can be designed to overcome the limitations of this study, which are discussed in detail below. Based on this study, we cannot say definitively that combination therapy is not warranted for treatment of invasive infection due to A. baumannii, but the results do suggest that rifampicin is not an ideal agent to be combined with colistin. [ABSTRACT FROM AUTHOR]

Emergence of multidrug-resistant Gram-negative nosocomial pathogens has led to resurgence of colistin use. Safety and efficacy data regarding colistin use in pediatric patients are sparse, while optimal dosage has not been defined. We present a case series of neonates and children without cystic fibrosis treated with various doses of colistin intravenously. The records of patients who received colistin in a tertiary-care hospital from January 2007 to March 2009 were reviewed. Thirteen patients (median age 5 years, range 22 days to 14 years) received 19 courses of colistin as treatment of pneumonia, central nervous system infection, bacteremia, or complicated soft tissue infection. The isolated pathogens were Acinetobacter baumannii, Enterobacter cloacae, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia. Daily dose of colistin (colistimethate) ranged between 40,000 and 225,000 IU/kg. Duration of administration ranged from 1 to 133 days. Other antimicrobials were co-administered in 18/19 courses. Increase of serum creatinine in one patient was associated with co-administration of colistin and gentamicin. Sixteen of 19 courses had a favorable outcome, and only two of the three deaths were infection-related. Colistin intravenous administration appears well tolerated even at higher than previously recommended doses and of prolonged duration. [ABSTRACT FROM AUTHOR]

Study Objective. To determine clinical and microbiologic success in patients receiving adjunctive aerosolized antibiotics for the treatment of ventilator-associated pneumonia (VAP). Design. Retrospective medical record review. Setting. Level I trauma intensive care unit of a large academic medical center. Patients. Forty-nine patients (mean ± SD age 42 ± 19 yrs) who received aerosolized antibiotics for the treatment of a total of 60 episodes of VAP caused by Pseudomonas aeruginosa and/or Acinetobacter baumannii between January 2001 and July 2007. Measurements and Main Results. Patients were identified by using an existing database of patients with documented VAP at the study center. To receive a diagnosis of VAP, patients had to have bacterial growth of 105 or more colony-forming units/ml from a bronchoscopic bronchoalveolar lavage and new or changing infiltrate on chest radiograph, plus at least two of the following: abnormal body temperature (> 38°C or < 36°C), abnormal white blood cell count (> 10 or < 4 x 10³/mm³, or > 10% immature bands), or macroscopically purulent sputum. By reviewing patient data, we evaluated clinical and microbiologic success using standard definitions. The median (interquartile range) Injury Severity Score and admission Acute Physiology and Chronic Health Evaluation II score were 40 (29-45) and 17 (9-21), respectively. Pseudomonas aeruginosa, A. baumannii, or both were isolated in 45, 14, and 1 episode(s), respectively. Eighteen VAP episodes included additional bacteria. Aerosolized tobramycin, amikacin, and colistimethate were used in 44, 9, and 9 episodes, respectively. Systemic antibiotics were used in 59 (98%) of the 60 episodes. Clinical success was achieved in 36 (73%) of the 49 first episodes of VAP, 8 (73%) of 11 subsequent episodes, 17 (85%) of 20 episodes that were failing intravenous monotherapy, and 30 (79%) of 38 episodes with multidrug-resistant P. aeruginosa or A. baumannii. Microbiologic success was achieved in 29 (71%) of 41 evaluable episodes. Six patients died from VAE Conclusion. Treatment with adjunctive aerosolized antibiotics was associated with a good response rate in critically ill trauma patients with VAP due to nonfermenting gram-negative bacilli. It is noteworthy that episodes of VAP that followed intravenous therapy failure and/or that were due to multidrug-resistant organisms responded well. [ABSTRACT FROM AUTHOR]

Summary: Objective: To assess the efficacy and toxicity of intravenous colistin in the treatment of infections due to multidrug-resistant gram-negative bacteria. Methods: Retrospective cohort study. Results: Sixty patients received colistin sulphomethate sodium (mean dose, 4.4mg/kg/day; median duration, 20days). The main infections were pneumonia or tracheobronchitis (63.3%), intra-abdominal (10%), urinary tract (8.3%), and surgical site infection (6.6%), primary bacteremia (5%), catheter infection (3.3%), meningitis (1.6%), and soft-tissue infection (1.6%). The responsible bacteria were Acinetobacter spp. (50%), P. aeruginosa (23.3%), K. pneumoniae (13.3%), Enterobacter spp. (10%), E. coli (1.6%), and S. maltophilia (1.6%). Eight patients (13%) received colistin monotherapy, and 52 (87%) received combination therapy with other antibiotics such as beta-lactams (15 cases), aminoglycosides (14), beta-lactams and aminoglycosides (15), or ciprofloxacin (8). A favourable response was observed in 43 cases (71.7%). Overall mortality was 26.7%. Despite the common use of combination therapy with aminoglycosides (48%), nephrotoxicity during colistin therapy was observed in only 10.9% of patients; most of them had previous renal failure. Conclusion: Colistin appears to be an effective and safe drug for therapy of severe infections due to multidrug-resistant gram-negative bacteria. Despite the concomitant use of aminoglycosides in a high proportion of patients, renal toxicity was an uncommon adverse event. [Copyright &y& Elsevier]