A Retrospective Case-Control Study of Eravacycline for the Treatment of Carbapenem-Resistant Acinetobacter Infections in Patients With Burn Injuries

Thermal injuries lead to a deficiency in one's natural, protective barrier, resulting in increased susceptibility to pathogens, and often require multiple courses of broad-spectrum antibiotics. Eravacycline (ERA) has shown adequate in vitro activity against multiple multi-drug resistant (MDR) pathogens including Acinetobacter sp. Due to the increasing prevalence of MDR bacteria and the heightened susceptibility of patients with burns to infection, studies are needed to examine the clinical effect of eravacycline in this population. The objective of this retrospective, case-control study was to compare the outcomes of patients with thermal injuries treated with eravacycline versus a matched control for carbapenem-resistant Acinetobacter baumannii (CRAB) infections. Patients with thermal injury admitted to an American Burn Associated-verified burn center from May 1, 2019 to July 31, 2022, who received eravacycline, were randomly matched 4:1 to a historical cohort using a previously established, de-identified dataset of patients treated with colistimethate sodium (CMS) in the same burn center (March 1, 2009 to March 31, 2014), based on % total body surface area (%TBSA), age, and CRAB. A composite favorable outcome was defined as 30-day survival, completion of the course, lack of 14-day recurrence, and lack of acute kidney injury (AKI). Treatment with eravacycline over CMS was not more or less likely to be associated with a favorable response [odds ratio (95% confidence interval), 2.066 (0.456-9.361), P = .347]. Patients treated with CMS had nearly 9-fold higher odds of new-onset AKI versus ERA [8.816 (0.911-85.308), P = .06]. Adverse events were uncommon in the ERA group. There was no difference in mortality.

Adverse Events and Drug Resistance in Critically Ill Patients Treated with Colistimethate Sodium: A Review of the Literature

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.

A Novel Validated Injectable Colistimethate Sodium Analysis Combining Advanced Chemometrics and Design of Experiments

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 C₈ 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.

Colistin Nephrotoxicity: Meta-Analysis of Randomized Controlled Trials

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.

Colistimethate Acidic Hydrolysis Revisited: Arrhenius Equation Modeling Using UPLC-QToF MS

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.

ColistinDose, a Mobile App for Determining Intravenous Dosage Regimens of Colistimethate in Critically Ill Adult Patients: Clinician-Centered Design and Development Study

Background

Determining a suitable dose of intravenous colistimethate is challenging because of complicated pharmacokinetics, confusing terminology, and the potential for renal toxicity. Only recently have reliable pharmacokinetic/pharmacodynamic data and dosing recommendations for intravenous colistimethate become available.

Objective

The aim of this work was to develop a clinician-friendly, easy-to-use mobile app incorporating up-to-date dosing recommendations for intravenous colistimethate in critically ill adult patients.

Methods

Swift programming language and common libraries were used for the development of an app, ColistinDose, on the iPhone operating system (iOS; Apple Inc). The compatibility among different iOS versions and mobile devices was validated. Dosing calculations were based on equations developed in our recent population pharmacokinetic study. Recommended doses generated by the app were validated by comparison against doses calculated manually using the appropriate equations.

Results

ColistinDose provides 3 major functionalities, namely (1) calculation of a loading dose, (2) calculation of a daily dose based on the renal function of the patient (including differing types of renal replacement therapies), and (3) retrieval of historical calculation results. It is freely available at the Apple App Store for iOS (version 9 and above). Calculated doses accurately reflected doses recommended in patients with varying degrees of renal function based on the published equations. ColistinDose performs calculations on a local mobile device (iPhone or iPad) without the need for an internet connection.

Conclusions

With its user-friendly interface, ColistinDose provides an accurate and easy-to-use tool for clinicians to calculate dosage regimens of intravenous colistimethate in critically ill patients with varying degrees of renal function. It has significant potential to avoid the prescribing errors and patient safety issues that currently confound the clinical use of colistimethate, thereby optimizing patient treatment.

Nephrotoxicity of Polymyxins: Is There Any Difference between Colistimethate and Polymyxin B?

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.

Colistin Use in Patients With Reduced Kidney Function

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.

Colistin: understanding and applying recent pharmacokinetic advances

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.

Stenotrophomonas infection in a patient with glucose-6-phosphate dehydrogenase deficiency

The drug of choice for treatment of Stenotrophomonas maltophilia is sulfamethoxazole/trimethoprim, and second-line therapy usually consists of a fluoroquinolone. However, in patients with glucose-6-phosphate dehydrogenase deficiency, neither sulfamethoxazole/trimethoprim nor a fluoroquinolone is a preferred option as it may result in hemolysis. Currently, there is a paucity of data regarding treatment of S maltophilia infection in these patients. This case report presents a patient who was successfully treated with doxycycline and inhaled colistimethate.