High extracellular levels of cefpirome in unaffected and infected lung tissue of patients

Antimicrobial Drug Penetration Is Enhanced by Lung Tissue Inflammation and Injury

Rationale: Pneumonia is a frequent and feared complication in intubated critically ill patients. Tissue concentrations of antimicrobial drugs need to be sufficiently high to treat the infection and also prevent development of bacterial resistance. It is uncertain whether pulmonary inflammation and injury affect antimicrobial drug penetration into lung tissue.Objectives: To determine and compare tissue and BAL fluid concentrations of ceftaroline fosamil and linezolid in a model of unilateral acute lung injury in pigs and to evaluate whether dose adjustment is necessary to reach sufficient antimicrobial concentrations in injured lung tissue.Methods: After induction of unilateral acute lung injury, ceftaroline fosamil and linezolid were administered intravenously. Drug concentrations were measured in lung tissue through microdialysis and in blood and BAL fluid samples during the following 8 hours. The primary endpoint was the tissue concentration area under the concentration curve in the first 8 hours (AUC0-8 h) of the two antimicrobial drugs.Measurements and Main Results: In 10 pigs, antimicrobial drug concentrations were higher in inflamed and injured lung tissue compared with those in uninflamed and uninjured lung tissue (median ceftaroline fosamil AUC0-8 h [and interquartile range] = 26.7 mg ⋅ h ⋅ L-1 [19.7-39.0] vs. 16.0 mg ⋅ h ⋅ L-1 [13.6-19.9], P = 0.02; median linezolid AUC0-8 h 76.0 mg ⋅ h ⋅ L-1 [68.1-96.0] vs. 54.6 mg ⋅ h ⋅ L-1 [42.7-60.9], P = 0.01), resulting in a longer time above the minimal inhibitory concentration and in higher peak concentrations and dialysate/plasma ratios. Penetration into BAL fluid was excellent for both antimicrobials, but without left-to-right differences (ceftaroline fosamil, P = 0.78; linezolid, P = 1.00).Conclusions: Tissue penetration of two commonly used antimicrobial drugs for pneumonia is enhanced by early lung tissue inflammation and injury, resulting in longer times above the minimal inhibitory concentration. Thus, lung tissue inflammation ameliorates antimicrobial drug penetration during the acute phase.

Understanding the nebulisation of antibiotics: the key role of lung microdialysis studies

BACKGROUND

Nebulisation of antibiotics is a promising treatment for ventilator-associated pneumonia (VAP) caused by multidrug-resistant organisms. Ensuring effective antibiotic concentrations at the site of infection in the interstitial space fluid is crucial for clinical outcomes. Current assessment methods, such as epithelial lining fluid and tissue homogenates, have limitations in providing longitudinal pharmacokinetic data.

MAIN BODY

Lung microdialysis, an invasive research technique predominantly used in animals, involves inserting probes into lung parenchyma to measure antibiotic concentrations in interstitial space fluid. Lung microdialysis offers unique advantages, such as continuous sampling, regional assessment of antibiotic lung concentrations and avoidance of bronchial contamination. However, it also has inherent limitations including the cost of probes and assay development, the need for probe calibration and limited applicability to certain antibiotics. As a research tool in VAP, lung microdialysis necessitates specialist techniques and resource-intensive experimental designs involving large animals undergoing prolonged mechanical ventilation. However, its potential impact on advancing our understanding of nebulised antibiotics for VAP is substantial. The technique may enable the investigation of various factors influencing antibiotic lung pharmacokinetics, including drug types, delivery devices, ventilator settings, interfaces and disease conditions. Combining in vivo pharmacokinetics with in vitro pharmacodynamic simulations can become feasible, providing insights to inform nebulised antibiotic dose optimisation regimens. Specifically, it may aid in understanding and optimising the nebulisation of polymyxins, effective against multidrug-resistant Gram-negative bacteria. Furthermore, lung microdialysis holds promise in exploring novel nebulisation therapies, including repurposed antibiotic formulations, bacteriophages and immunomodulators. The technique's potential to monitor dynamic biochemical changes in pneumonia, such as cytokines, metabolites and inflammation/infection markers, opens avenues for developing theranostic tools tailored to critically ill patients with VAP.

CONCLUSION

In summary, lung microdialysis can be a potential transformative tool, offering real-time insights into nebulised antibiotic pharmacokinetics. Its potential to inform optimal dosing regimen development based on precise target site concentrations and contribute to development of theranostic tools positions it as key player in advancing treatment strategies for VAP caused by multidrug-resistant organisms. The establishment of international research networks, exemplified by LUMINA (lung microdialysis applied to nebulised antibiotics), signifies a proactive step towards addressing complexities and promoting multicentre experimental studies in the future.

Separation and characterization of impurities and isomers in cefpirome sulfate by liquid chromatography/tandem mass spectrometry and a summary of the fragmentation pathways of oxime-type cephalosporins

RATIONALE

Although the identification of degradation products of cefpirome sulfate has been reported, there has been no report concerning the impurities in bulk samples of this compound. To meet the requirements of the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use, the structures of impurities whose content are over 0.1% need to be confirmed. Thus, characterization of the impurities in cefpirome sulfate bulk samples is critical for controlling the production of this drug.

METHODS

The structures of cefpirome sulfate impurities were investigated using two-dimensional liquid chromatography (LC) coupled to electrospray ionization tandem mass spectrometry. In the first LC dimension, a Kromasil 100-5C18 column (4.6 mm × 250 mm, 5 μm) was used, and the mobile phases were 0.03 M ammonium dihydrogen phosphate solution and acetonitrile. In the second dimension, the column was a Shimadzu Shim-pack GISS C18 column (50 mm × 2.1 mm, 1.9 μm), and the mobile phases were 10 mM ammonium formate solution and methanol. An ion trap time-of-flight mass spectrometer operated in both positive and negative ion mode was employed in this study.

RESULTS

Nine impurities and isomers in cefpirome sulfate, eight of which were previously unknown, were separated and characterized. Structures were proposed for the eight unknown compounds based on the MSn fragmentation data. The degradation behavior of cefpirome sulfate was also studied.

CONCLUSIONS

Based on the characterization of impurities and isomers, this study could be used to improve the quality control of the cefpirome sulfate drug recommended in pharmacopoeias. The degradation behavior of cefpirome sulfate provides a basis for the selection of storage conditions.

Lung Collapse during Mini-Thoracotomy Reduces Penetration of Cefuroxime to the Tissue: Interstitial Microdialysis Study in Animal Models

Background: Single-lung ventilation facilitates surgical exposure during minimally invasive cardiac surgery. However, a deeper knowledge of antibiotic distribution within a collapsed lung is necessary for effective antibiotic prophylaxis of pneumonia. Patients and Methods: The pharmacokinetics/pharmacodynamics (PK/PD) of cefuroxime were compared between the plasma and interstitial fluid (ISF) of collapsed and ventilated lungs in 10 anesthetized pigs, which were ventilated through a double-lumen endotracheal cannula. Cefuroxime (20 mg/kg) was administered in single 30-minute intravenous infusion. Samples of blood and lung microdialysate were collected until six hours post-dose. Ultrafiltration, in vivo retrodialysis, and high-performance liquid chromatography-tandem mass spectrometry were used to determine plasma and ISF concentrations of free drug. The concentrations were examined with non-compartmental analysis and compartmental modeling. Results: The concentration of free cefuroxime in ISF was lower in the non-ventilated lung than the ventilated one, evidenced by a lung penetration factor of 47% versus 63% (p < 0.05), the ratio between maximum concentrations (65%, p < 0.05), and the ratio between the areas under the concentration-time curve (78%, p = 0.12). The time needed to reach a minimum inhibitory concentration (MIC) was 30%-40% longer for a collapsed lung than for a ventilated one. In addition, a delay of 10-40 minutes was observed for lung ISF compared with plasma. The mean residence time values (ISF collapsed lung > ISF ventilated lung > plasma) could explain the absence of practically important differences in the time interval with the concentration of cefuroxime exceeding the MICs of sensitive strains (≤4 mg/L). Conclusion: The concentration of cefuroxime in the ISF of a collapsed porcine lung is lower than in a ventilated one; furthermore, its equilibration with plasma is delayed. Administration of the first cefuroxime dose earlier or at a higher rate may be warranted, as well as dose intensification of the perioperative prophylaxis of pneumonia caused by pathogens with higher MICs.

Intrapulmonary pharmacokinetics of cefiderocol, a novel siderophore cephalosporin, in healthy adult subjects

BACKGROUND

Cefiderocol, a novel siderophore cephalosporin, has shown potent activity against Gram-negative bacteria, including MDR pathogens. Cefiderocol is under clinical investigation for the treatment of serious Gram-negative infections including nosocomial pneumonia.

OBJECTIVES

This study assessed intrapulmonary penetration after a single intravenous dose of cefiderocol (2000 mg infused over 60 min) in healthy adult males.

MATERIALS AND METHODS

Each subject underwent one bronchoscopy with bronchoalveolar lavage (BAL) to collect BAL fluid (BALF). Fifteen subjects were assigned to one of three collection timepoints (1, 2 or 4 h from start of infusion). Five additional subjects were assigned to a collection timepoint at 6 h, which was added based on concentration data between 1 and 4 h predicting measurable BALF cefiderocol concentrations at 6 h.

RESULTS

Cefiderocol concentrations in plasma, epithelial lining fluid (ELF) and alveolar macrophages (AMs) were calculated for each subject. The ELF concentration of cefiderocol was 13.8, 6.69, 2.78 and 1.38 mg/L at 1, 2, 4 and 6 h after single intravenous dosing, respectively. Over 6 h, geometric mean concentration ratios ranged from 0.0927 to 0.116 for ELF to total plasma and from 0.00496 to 0.104 for AMs to total plasma. AUC ratios of ELF and AMs to plasma were 0.101 and 0.0177 based on total drug in plasma, respectively, and 0.239 and 0.0419 based on free drug in plasma, respectively. There were no major drug-related adverse events.

CONCLUSIONS

Results of this study indicate that cefiderocol penetrates into ELF, and ELF and plasma concentrations appear to be parallel.

Considerations for effect site pharmacokinetics to estimate drug exposure: concentrations of antibiotics in the lung

Bronchoalveolar lavage (BAL) and microdialysis have become the most reliable and relevant methods for measuring lung concentrations of antibiotics, with the majority of BAL studies involving either healthy adult subjects or patients undergoing diagnostic bronchoscopy. Emphasis on the amount of drug that reaches the site of infection is increasingly recognized as necessary to determine whether a dose selection will translate to good clinical outcomes in the treatment of patients with pneumonia. Observed concentrations and/or parameters of exposure (e.g. area-under-the-curve) need to be incorporated with pharmacokinetic-pharmacodynamic indices so that rational dose selection can be identified for specific pathogens and types of pneumonic infection (community-acquired vs hospital-acquired bacterial pneumonia, including ventilator-associated bacterial pneumonia). Although having measured plasma or lung concentration-time data from critically ill patients to incorporate into pharmacokinetic-pharmacodynamic models is very unlikely during drug development, it is essential that altered distribution, augmented renal clearance, and renal or hepatic dysfunction should be considered. Notably, the number of published studies involving microdialysis and intrapulmonary penetration of antibiotics has been limited and mainly involve beta-lactam agents, levofloxacin, and fosfomycin. Opportunities to measure in high-resolution effect site spatial pharmacokinetics (e.g. with MALDI-MSI or PET imaging) and in vivo continuous drug concentrations (e.g. with aptamer-based probes) now exist. Going forward these studies could be incorporated into antibiotic development programs for pneumonia in order to further increase the probability of candidate success.

The radiolytic studies of cefpirome sulfate in the solid state

The possibility of applying radiation sterilization to cefpirome sulfate was investigated. The lack of changes in the chemical structure of cefpirome sulfate irradiated with a dose of 25 kGy, required to attain sterility, was confirmed by UV, FT-IR, Raman, DSC and chromatographic methods. Some radical defects with concentration no more than over a several dozen ppm were created by radiation. The antibacterial activity of cefpirome sulfate for two Gram-positive and three Gram-negative strains was changed. The radiation sterilised cefpirome sulfate was not in vitro cytotoxic against fibroblast cells.

Cavitary penetration of levofloxacin among patients with multidrug-resistant tuberculosis

A better understanding of second-line drug (SLD) pharmacokinetics, including cavitary penetration, may help optimize SLD dosing. Patients with pulmonary multidrug-resistant tuberculosis (MDR-TB) undergoing adjunctive surgery were enrolled in Tbilisi, Georgia. Serum was obtained at 0, 1, 4, and 8 h and at the time of cavitary removal to measure levofloxacin concentrations. After surgery, microdialysis was performed using the ex vivo cavity, and levofloxacin concentrations in the collected dialysate fluid were measured. Noncompartmental analysis was performed, and a cavitary-to-serum levofloxacin concentration ratio was calculated. Twelve patients received levofloxacin for a median of 373 days before surgery (median dose, 11.8 mg/kg). The median levofloxacin concentration in serum (Cmax) was 6.5 μg/ml, and it was <2 μg/ml in 3 (25%) patients. Among 11 patients with complete data, the median cavitary concentration of levofloxacin was 4.36 μg/ml (range, 0.46 to 8.82). The median cavitary/serum levofloxacin ratio was 1.33 (range, 0.63 to 2.36), and 7 patients (64%) had a ratio of >1. There was a significant correlation between serum and cavitary concentrations (r = 0.71; P = 0.01). Levofloxacin had excellent penetration into chronic cavitary TB lesions, and there was a good correlation between serum and cavitary concentrations. Optimizing serum concentrations will help ensure optimal cavitary concentrations of levofloxacin, which may enhance treatment outcomes.

Investigation of interaction studies of cefpirome with ACE-inhibitors in various buffers

This work describes a RP-HPLC method for the determination and interaction studies of cefpirome with ACE-inhibitors (captopril, enalapril and lisinopril) in various buffers. The separation and interaction of cefpirome with ACE-inhibitors was achieved on a Purospher Star, C18 (5 μm, 250×4.6 mm) column. Mobile phase consisted of methanol: water (80:20, v/v, pH 3.3); however, for the separation of lisinopril, it was modified to methanol-water (40:60, v/v, pH 3.3) and pumped at a flow rate of 1 mL min(-1). In all cases, UV detection was performed at 225 nm. Interactions were carried out in physiological pH i.e., pH 1 (simulated gastric juice), 4 (simulated full stomach), 7.4 (blood pH) and 9 (simulated GI), drug contents were analyzed by reverse phase high performance liquid chromatography. Method was found linear in the concentration range of 1.0-50.0 μg mL(-1) with correlation coefficient (r(2)) of 0.999. Precision (RSD%) was less than 2.0%, indicating good precision of the method and accuracy was 98.0-100.0%. Furthermore, cefpirome-ACE-inhibitors' complexes were also synthesized and results were elucidated on the basis of FT-IR, and (1)H NMR. The interaction results show that these interactions are pH dependent and for the co-administration of cefpirome and ACE-inhibitors, a proper interval should be given.

Stability studies of cefpirome sulfate in the solid state: Identification of degradation products

The process of degradation was studied by using an HPLC-DAD method. Four degradation products were identified with a hybrid ESI-Q-TOF mass spectrometer. The influence of temperature and relative air humidity (RH) on the stability of cefpirome sulfate was investigated. In the solid state the degradation of cefpirome sulfate was a first-order reaction depending on the substrate concentration. The kinetic and thermodynamic parameters of degradation were calculated.