The INHALE trial: multiple reasons for a negative result

Analysis and comparison of adverse events of colistin administered by different routes based on the FAERS database

OBJECTIVE

To analyze and compare the incidence of adverse events (AEs) associated with different administration routes of colistin, with the aim of providing a reference for its safe and effective clinical use.

METHODS

Adverse event (AE) reports related to colistin were retrieved from the FDA Adverse Event Reporting System (FAERS) database. The reporting trends were analyzed, and the Reporting Odds Ratio (ROR) and Proportional Reporting Ratio (PRR) for colistin-associated AEs were calculated. A comparative analysis was conducted to examine the occurrence of AEs under different administration routes of colistin.

RESULTS

A total of 13,043 AE reports were extracted from the FAERS database. Further analysis of 176 key AEs associated with colistin indicated a significant increase in the number of reports after 2021. The year and country of the reports showed heterogeneity across different administration routes. Intravenous (IV) administration of colistin was associated with the highest proportion of AEs, and heterogeneity was also observed in the types of AEs reported for inhaled and oral (PO) administration routes.

CONCLUSION

Compared to inhaled and PO administration routes, IV administration of colistin is more likely to result in AEs such as nephrotoxicity and drug ineffectiveness. Additionally, there are significant differences in the types of AEs associated with colistin across different administration routes.

In vitro killing of drug susceptible and multidrug resistant bacteria by amikacin considering pulmonary drug concentrations based on an inhaled formulation

Nosocomial infections with drug resistant bacteria impact morbidity and mortality, length of therapy and stay and the overall cost of treatment. Key pathogens with ventilator associated pneumonia may be drug-susceptible or multi-drug resistant and inhaled amikacin has been investigated as an adjunctive therapy option. High pulmonary drug concentrations (epithelial lining fluid [ELF]) along with minimal systemic toxicity is seen as an advantage to inhaled formulations. In vitro killing of bacteria using clinically relevant drug concentrations provide insight on bug-drug interactions. The aim of this study was to measure killing of clinical isolates of Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus and methicillin-susceptible S. aureus using the minimum inhibitory concentration (MIC), mutant prevention concentration (MPC) and median (976 µg/ml) ELF drug concentration for amikacin. Overall killing took longer at the MIC drug concentration and was inconsistent amongst the pathogens tested with the percentage of bacteria killed following 180 min of drug exposure ranging from growth in the presence of the drug to 95% kill. At the MPC drug concentrations, killing ranged from 55-88% for all pathogens following 30 min of drug exposure and increased to 99-100% following 180 min of drug exposure. At the ELF amikacin tested, killing was 81-100% following 20 min and 94-100% by 30 min of drug exposure. Rapid killing against MDR respiratory pathogens by amikacin ELF drug concentrations is encouraging.

Inhaled amikacin for pneumonia treatment and dissemination prevention: an experimental model of severe monolateral Pseudomonas aeruginosa pneumonia

BACKGROUND

Pseudomonas aeruginosa pneumonia is commonly treated with systemic antibiotics to ensure adequate treatment of multidrug resistant (MDR) bacteria. However, intravenous (IV) antibiotics often achieve suboptimal pulmonary concentrations. We therefore aimed to evaluate the effect of inhaled amikacin (AMK) plus IV meropenem (MEM) on bactericidal efficacy in a swine model of monolateral MDR P. aeruginosa pneumonia.

METHODS

We ventilated 18 pigs with monolateral MDR P. aeruginosa pneumonia for up to 102 h. At 24 h after the bacterial challenge, the animals were randomized to receive 72 h of treatment with either inhaled saline (control), IV MEM only, or IV-MEM plus inhaled AMK (MEM + AMK). We dosed IV MEM at 25 mg/kg every 8 h and inhaled AMK at 400 mg every 12 h. The primary outcomes were the P. aeruginosa burden and histopathological injury in lung tissue. Secondary outcomes included the P. aeruginosa burden in tracheal secretions and bronchoalveolar lavage fluid, the development of antibiotic resistance, the antibiotic distribution, and the levels of inflammatory markers.

RESULTS

The median (25-75th percentile) P. aeruginosa lung burden for animals in the control, MEM only, and MEM + AMK groups was 2.91 (1.75-5.69), 0.72 (0.12-3.35), and 0.90 (0-4.55) log10 CFU/g (p = 0.009). Inhaled therapy had no effect on preventing dissemination compared to systemic monotherapy, but it did have significantly higher bactericidal efficacy in tracheal secretions only. Remarkably, the minimum inhibitory concentration of MEM increased to > 32 mg/L after 72-h exposure to monotherapy in 83% of animals, while the addition of AMK prevented this increase (p = 0.037). Adjunctive therapy also slightly affected interleukin-1β downregulation. Despite finding high AMK concentrations in pulmonary samples, we found no paired differences in the epithelial lining fluid concentration between infected and non-infected lungs. Finally, a non-significant trend was observed for higher amikacin penetration in low-affected lung areas.

CONCLUSIONS

In a swine model of monolateral MDR P. aeruginosa pneumonia, resistant to the inhaled AMK and susceptible to the IV antibiotic, the use of AMK as an adjuvant treatment offered no benefits for either the colonization of pulmonary tissue or the prevention of pathogen dissemination. However, inhaled AMK improved bacterial eradication in the proximal airways and hindered antibiotic resistance.

Nebulized Antibiotics for Healthcare- and Ventilator-Associated Pneumonia

Global emergence of multidrug-resistant and extensive drug-resistant gram-negative bacteria has increased the risk of treatment failure, especially for healthcare- or ventilator-associated pneumonia (HAP/VAP). Nebulization of antibiotics, by providing high intrapulmonary antibiotic concentrations, represents a promising approach to optimize the treatment of HAP/VAP due to multidrug-resistant and extensive drug-resistant gram-negative bacteria, while limiting systemic antibiotic exposure. Aminoglycosides and colistin methanesulfonate are the most common nebulized antibiotics. Although optimal nebulized drug dosing regimen is not clearly established, high antibiotic doses should be administered using vibrating-mesh nebulizer with optimized ventilator settings to ensure safe and effective intrapulmonary concentrations. When used preventively, nebulized antibiotics reduced the incidence of VAP without any effect on mortality. This approach is not yet recommended and large randomized controlled trials should be conducted to confirm its benefit and explore the impact on antibiotic selection pressure. Compared with high-dose intravenous administration, high-dose nebulized colistin methanesulfonate seems to be more effective and safer in the treatment of ventilator-associated tracheobronchitis and VAP caused by multidrug resistant and extensive-drug resistant gram-negative bacteria. Adjunctive nebulized aminoglycosides could increase the clinical cure rate and bacteriological eradication in patients suffering from HAP/VAP due to multidrug-resistant and extensive drug-resistant gram-negative bacteria. As nebulized aminoglycosides broadly diffuse in the systemic circulation of patients with extensive bronchopneumonia, monitoring of plasma trough concentrations is recommended during the period of nebulization. Large randomized controlled trials comparing high dose of nebulized colistin methanesulfonate to high dose of intravenous colistin methanesulfonate or to intravenous new β-lactams in HAP/VAP due to multidrug-resistant and extensive drug-resistant gram-negative bacteria are urgently needed.

Nebulized antibiotics for ventilator-associated pneumonia: methodological framework for future multicenter randomized controlled trials

PURPOSE OF REVIEW

Although experimental evidence supports the use of nebulized antibiotics in ventilator-associated pneumonia (VAP), two recent multicenter randomized controlled trials (RCTs) have failed to demonstrate any benefit in VAP caused by Gram-negative bacteria (GNB). This review examines the methodological requirements concerning future RCTs.

RECENT FINDINGS

High doses of nebulized antibiotics are required to reach the infected lung parenchyma. Breath-synchronized nebulizers do not allow delivery of high doses. Mesh nebulizers perform better than jet nebulizers. Epithelial lining fluid concentrations do not reflect interstitial lung concentrations in patients receiving nebulized antibiotics. Specific ventilator settings for optimizing lung deposition require sedation to avoid patient's asynchrony with the ventilator.

SUMMARY

Future RCTs should compare a 3-5 day nebulization of amikacin or colistimethate sodium (CMS) to a 7-day intravenous administration of a new cephalosporine/ß-lactamase inhibitor. Inclusion criteria should be a VAP or ventilator-associated tracheobronchitis caused by documented extensive-drug or pandrug resistant GNB. If the GNB remains susceptible to aminoglycosides, nebulized amikacin should be administered at a dose of 40 mg/kg/day. If resistant to aminoglycosides, nebulized CMS should be administered at a dose of 15 millions international units (IU)/day. In VAP caused by pandrug-resistant GNB, 15 millions IU/day nebulized CMS (substitution therapy) should be compared with a 9 millions IU/day intravenous CMS.

Effectiveness and safety of adjunctive inhaled antibiotics for ventilator-associated pneumonia: A systematic review and meta-analysis of randomized controlled trials

INTRODUCTION

The efficacy and safety of adjunctive inhaled antibiotic therapy for ventilator-associated pneumonia (VAP) was systematically reviewed based on updated studies.

METHODS

We searched four databases and four clinical trial registration platforms to identify relevant studies published prior to May 19, 2020. Randomized controlled trials (RCTs) assessing adjunctive antibiotic inhalation treatment for VAP patients were eligible for this review. Two reviewers independently screened the articles and extracted the data. Information on inhaled therapy and clinical outcomes was collected. Study quality was assessed with the Cochrane risk of bias tool. The meta-analysis was conducted with Review Manager and R software. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) guidelines were used to evaluate the quality of evidence for each pooled outcome.

RESULTS

Eleven RCTs and 1210 patients were included in this analysis after the application of the inclusion and exclusion criteria. Compared with the use of intravenous injection alone, the use of adjunctive inhaled antibiotic therapy improved the rates of clinical cure (relative risk (RR) 1.13, 95% CI [1.02,1.26]) and microbiological eradication (RR 1.45, 95% CI [1.19,1.76]) in VAP patients. However, despite these improvements, mortality was not reduced (RR 1.00, 95% CI [0.82,1.21]). Adjunctive antibiotics delivered through the respiratory tract were not associated with a higher risk of renal impairment but were associated with an increased risk of bronchospasm (RR 2.74, 95% CI [1.31,5.73] during treatment.

CONCLUSIONS

Adjunctive inhaled antibiotics improved the clinical outcomes in VAP patients, but the increased rates clinical cure and microbiological eradication were not associated with reduced mortality. The use of nebulized antibiotics is not supported by the currently available evidence as a routine therapeutic strategy for VAP.

PROSPERO REGISTRATION NUMBER

CRD42020186970.

Nebulized Colistin in Ventilator-Associated Pneumonia and Tracheobronchitis: Historical Background, Pharmacokinetics and Perspectives

Clinical evidence suggests that nebulized colistimethate sodium (CMS) has benefits for treating lower respiratory tract infections caused by multidrug-resistant Gram-negative bacteria (GNB). Colistin is positively charged, while CMS is negatively charged, and both have a high molecular mass and are hydrophilic. These physico-chemical characteristics impair crossing of the alveolo-capillary membrane but enable the disruption of the bacterial wall of GNB and the aggregation of the circulating lipopolysaccharide. Intravenous CMS is rapidly cleared by glomerular filtration and tubular excretion, and 20-25% is spontaneously hydrolyzed to colistin. Urine colistin is substantially reabsorbed by tubular cells and eliminated by biliary excretion. Colistin is a concentration-dependent antibiotic with post-antibiotic and inoculum effects. As CMS conversion to colistin is slower than its renal clearance, intravenous administration can lead to low plasma and lung colistin concentrations that risk treatment failure. Following nebulization of high doses, colistin (200,000 international units/24h) lung tissue concentrations are > five times minimum inhibitory concentration (MIC) of GNB in regions with multiple foci of bronchopneumonia and in the range of MIC breakpoints in regions with confluent pneumonia. Future research should include: (1) experimental studies using lung microdialysis to assess the PK/PD in the interstitial fluid of the lung following nebulization of high doses of colistin; (2) superiority multicenter randomized controlled trials comparing nebulized and intravenous CMS in patients with pandrug-resistant GNB ventilator-associated pneumonia and ventilator-associated tracheobronchitis; (3) non-inferiority multicenter randomized controlled trials comparing nebulized CMS to intravenous new cephalosporines/ß-lactamase inhibitors in patients with extensive drug-resistant GNB ventilator-associated pneumonia and ventilator-associated tracheobronchitis.

Impact of the Epithelial Lining Fluid Milieu on Amikacin Pharmacodynamics Against Pseudomonas aeruginosa

Background

Even though nebulised administration of amikacin can achieve high epithelial lining fluid concentrations, this has not translated into improved patient outcomes in clinical trials. One possible reason is that the cellular and chemical composition of the epithelial lining fluid may inhibit amikacin-mediated bacterial killing.

Objective

The objective of this study was to identify whether the epithelial lining fluid components inhibit amikacin-mediated bacterial killing.

Methods

Two amikacin-susceptible (minimum inhibitory concentrations of 2 and 8 mg/L) Pseudomonas aeruginosa isolates were exposed in vitro to amikacin concentrations up to 976 mg/L in the presence of an acidic pH, mucin and/or surfactant as a means of simulating the epithelial lining fluid, the site of bacterial infection in pneumonia. Pharmacodynamic modelling was used to describe associations between amikacin concentrations, bacterial killing and emergence of resistance.

Results

In the presence of broth alone, there was rapid and extensive (> 6 − log₁₀) bacterial killing, with emergence of resistance identified in amikacin concentrations < 976 mg/L. In contrast, the rate and extent of bacterial killing was reduced (≤ 5 − log₁₀) when exposed to an acidic pH and mucin. Surfactant did not appreciably impact the bacterial killing or resistance emergence when compared with broth alone for either isolate. The combination of mucin and an acidic pH further reduced the rate of bacterial killing, with the maximal bacterial killing occurring 24 h following initial exposure compared with approximately 4–8 h for either mucin or an acidic pH alone.

Conclusions

Our findings indicate that simulating the epithelial lining fluid antagonises amikacin-mediated killing of P. aeruginosa, even at the high concentrations achieved following nebulised administration.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40268-021-00344-5.

Inhaled antibiotics during mechanical ventilation-why it will work

Inhaled antibiotics are a common therapy among patients suffering recurrent or chronic pulmonary infections. Their use is less frequent in acutely ill patients despite a strong theoretical rationale and growing evidence of their efficiency, safety and beneficial effect on reducing bacterial resistance emergence. Clinical trials of inhaled antibiotics have shown contradictory results among mechanically ventilated patients. The optimal nebulization setup, not always implemented in all trials, the difficulty to identify the population most likely to benefit and the testing of various therapeutic strategies such as adjunctive versus alternative to systemic antibiotics may explain the disparity in trial results. The present review first presents the reasons why inhaled antibiotics have to be developed and the benefits to be expected of inhaled anti-infectious therapy among mechanically ventilated patients. A second part develops the constraints of aerosolized therapies that one has to be aware of and the simple actions required during nebulization to ensure optimal delivery to the distal lung parenchyma. Positive and negative studies concerning inhaled antibiotics are compared to understand the discrepancies of their findings and conclusions. The last part presents current developments and perspective which will likely turn it into a fully successful therapeutic modality, and makes the link between inhaled antibiotics and inhaled anti-infectious therapy.