Pharmacokinetics/pharmacodynamics and therapeutic drug monitoring of ceftazidime/avibactam administered by continuous infusion in patients with MDR Gram-negative bacterial infections

Evaluation of Ceftazidime-avibactam and Ceftolozane-tazobactam Prescriptions in a Tertiary Hospital for Children in France: An Observational Study, 2017-2022

BACKGROUND

Infections caused by drug-resistant Gram-negative bacteria, including carbapenem-resistant Enterobacterales and Pseudomonas aeruginosa, are emerging in pediatric hospitals. New ß-lactam/ ß-lactamase inhibitor combinations exhibit activity against these pathogens; however, there is limited data regarding their use in pediatric populations.

OBJECTIVES

The study aimed to describe the characteristics of ceftazidime-avibactam (CAZ/AVI) and ceftolozane-tazobactam (C/T) prescriptions in children and assess their appropriateness.

METHODS

We retrospectively analyzed all CAZ/AVI or C/T prescriptions in children hospitalized in a French tertiary hospital between 2017 and 2022. All clinical, biological, and pharmacological data were collected prospectively as part of the antibiotic monitoring program set up by our antimicrobial stewardship (AMS) team.

RESULTS

In total, 50 CAZ/AVI and 25 C/T prescriptions were recorded, which concerned 21 and 20 patients, respectively. All patients had an underlying chronic condition. Most prescriptions originated from Pediatric Intensive Care Units and the Department of Pediatric Pulmonology and were mainly initiated for respiratory tract infections (n = 41/50, 82% of the CAZ/AVI prescriptions and n = 14/25, 56% of the C/T prescriptions). P. aeruginosa was the primary pathogen in documented infections for both CAZ/AVI and C/T prescriptions (n = 26/48, 54% and n = 16/19, 84%, respectively). Almost all prescriptions of CAZ/AVI and C/T were considered appropriate (n = 47/50, 94% for CAZ/AVI and n = 23/25, 92% for C/T, respectively) by the AMS team. Both CAZ/AVI and C/T treatments were well tolerated and resulted in clinical success in 33 (66%) and 19 (76%) cases, respectively.

CONCLUSION

Our study suggests that CAZ/AVI and C/T are reasonable treatment options for children infected with Gram-negative pathogens resistant to carbapenems.

Difficult-to-Treat Pseudomonas aeruginosa Infections in Critically Ill Patients: A Comprehensive Review and Treatment Proposal

The management of infections caused by difficult-to-treat Pseudomonas aeruginosa in critically ill patients poses a significant challenge. Optimal antibiotic therapy is crucial for patient prognosis, yet the numerous resistance mechanisms of P. aeruginosa, which may even combine, complicate the selection of an appropriate antibiotic. In this review, we examine the epidemiology, resistance mechanisms, risk factors, and available and future therapeutic options, as well as strategies for treatment optimization. Finally, we propose a treatment algorithm to facilitate decision making based on the resistance patterns specific to each Intensive Care Unit.

'Real-life' approach to applying PK/PD principles in infectious diseases clinical practice without access to prompt TDM

INTRODUCTION

Infectious disease treatments are transitioning from a one-size-fits-all approach to a more tailored approach. The increasing adoption of therapeutic drug monitoring (TDM) of antimicrobials is a clear example of this trend. Routine antimicrobial TDM in critically ill patients should be mandatory. Unfortunately, nowadays, only expert centers can provide it. Given the crucial nature of the first hours/days for achieving a favorable clinical outcome, empirical antibiotic therapy with an adequate choice of drug, dose and administration modalities is fundamental.

AREAS COVERED

We outline common scenarios encountered in clinical practice, such as in edematous patients, hypoalbuminemia, patients with liver and renal diseases, patients under renal replacement therapy or extracorporeal membrane oxygenation (ECMO), over or under-weight patients, in old adults and cases of infections caused by relatively high minimum inhibitory concentration (MIC) pathogens. Various clinical situations were analyzed with the help of the available literature (PubMed/MEDLINE/Google Scholar and books written by experts in pharmacology and infectious diseases).

EXPERT OPINION

In these different scenarios, we reported common examples of optimizing drug utilization to maximize therapeutic outcomes, reduce incorrect prescriptions and limit the emergence of antimicrobial resistance.

Simultaneous determination of three β-Lactam/β-lactamase inhibitor combinations in critically ill patients by UPLC-MS/MS

β-Lactam/β-lactamase inhibitors (BL/BLIs) are widely used in critically ill patients. Recent research has shown the importance of therapeutic drug monitoring (TDM) of BLs, but few studies have highlighted the importance of detecting BLIs in critically ill patients. In our laboratory, we have developed and validated a simple and robust method for the determination of ceftazidime, cefoperazone, piperacillin, avibactam, sulbactam and tazobactam in human plasma by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Sample preparation was by protein precipitation of 100 µL of sample, followed by chromatographic separation on an ACQUITY UPLC® BEH C18 column (2.1 × 50 mm, 1.7 µm) and mass spectrometric detection using a SHIMADZU 8050CL in multiple reaction monitoring (MRM) mode. The method was fully validated for selectivity, carry-over, linearity, lower limit of quantification, matrix effect, extraction recovery, stability and dilution integrity. The results of the TDM could provide feedback to clinicians and allow timely adjustment of dosing regimens in critically ill patients. The method is suitable for routine TDM and has been successfully applied to the clinical determination of 81 plasma concentrations in 44 patients.

Impact of renal-adjusted ceftazidime/avibactam in patients with KPC-producing Klebsiella pneumoniae bloodstream infection: a retrospective cohort study

Background

Bloodstream infections (BSIs) caused by KPC-producing Klebsiella pneumoniae (KPC-Kp) are still associated with high mortality, and the game-changing drug ceftazidime/avibactam has shown suboptimal pharmacokinetics in some clinical settings. Ceftazidime/avibactam renal dose adjustment has recently been identified as an independent risk factor for mortality.

Objectives

To investigate the effect of ceftazidime/avibactam renal dose adjustment on mortality.

Methods

Patients with KPC-Kp BSI treated with a ceftazidime/avibactam-based regimen were retrospectively collected and analysed. The primary outcome was mortality at 7, 14 and 30 days after the start of definitive ceftazidime/avibactam antibiotic therapy. Renal function was estimated using the CKD-EPI equation.

Results

One hundred and ten patients with KPC-Kp BSI treated with a ceftazidime/avibactam-based regimen were included. Full-dose ceftazidime/avibactam (7.5 g daily) was prescribed to 82 patients (74.5%), while 28 patients (25.5%) received a renal-adjusted dose (17 patients due to chronic renal disease or haemodialysis, 11 patients due to infection-related acute kidney injury), with a median of 1.9 g daily. At multivariable analysis, receiving a reduced dose of ceftazidime/avibactam was independently associated with mortality (HR 4.47, 95% CI 1.09-18.03, P = 0.037), along with intra-abdominal or lower respiratory tract infections as source of BSI (HR 5.42, 95% CI 1.77-16.55, P = 0.003), septic shock (HR 6.99, 95% CI 1.36-35.87, P = 0.020) and SARS-CoV-2 coinfection (HR 10.23, 95% CI 2.69-38.85, P = 0.001).

Conclusions

Dose reduction of ceftazidime/avibactam according to renal function in patients with KPC-Kp BSI seems to be independently associated with higher mortality. This may be possibly due to inadequate exposure provided by the recommended doses for renal impairment.

Renal function and its impact on the concentration of ceftazidime-avibactam: A cross-sectional study

OBJECTIVE

This study measured the effect of renal function on the plasma concentrations of ceftazidime and avibactam in critically ill patients. We also sought to measure the concentration ratio of ceftazidime to avibactam.

METHODS

This was a cohort study at a tertiary referral centre in Italy, on patients treated with continuous infusion of ceftazidime-avibactam (CAZ-AVI) between November 2019 and December 2023. The association between creatine clearance (CrCl) and free plasma ceftazidime and avibactam concentration, as well as CAZ-AVI ratio was explored to assess correlation and potential risk to fail to achieve target therapeutic concentration.

RESULTS

Fifty-two patients, predominantly male (75%), with a median age of 68.5 y were included. Our analyses provided strong evidence for inverse correlation between CrCl and both free-CAZ (r = -0.627; R2 = 0.3936; P < 0.001) and free-AVI plasma concentration (r = -0.619; R2 = 0.3832; P < 0.001). Overall CrCl alone could explain about 40% of overall variation of either free-CAZ and free-AVI. Linear models suggest that free-CAZ and free-AVI concentration drop of about 7.31% and 9.23% for each 10 point increase of CrCl, respectively. Assessment of the CAZ-AVI ratio supports a direct linear association with CrCl suggesting that free-AVI concentration is more affected by CrCl variation than free-CAZ concentration. Patients with CrCl ≥130 mL/min showed a significantly higher risk of suboptimal drug exposure (i.e., less than 4 times the MIC) both to CAZ and AVI.

CONCLUSION

The findings emphasise the need for individualised dosing strategies of CAZ-AVI based on renal function, for antibiotics used in critically ill patients. The study suggests that underdosing in patients with high CrCl is likely to be common and as such could affect drug effectiveness.

Dosing Evaluation of Ceftazidime-Avibactam in Intensive Care Unit Patients Based on Pharmacokinetic/Pharmacodynamic (PK/PD) Modeling and Simulation

P. aeruginosa is the most common microorganism involved in many ICU-acquired infections. A correct dosage regimen is pivotal to avoiding resistance development, worse outcomes and higher mortality rates. The aim of this study was to perform a pharmacokinetic-pharmacodynamic (PK/PD) evaluation of recommended dosing regimens of ceftazidime-avibactam (CAZ-AVI) in ICU patients with different degrees of renal function for a specific strain of Pseudomonas aeruginosa. A semi-mechanistic PK/PD model has been developed. It allows for the simulation of CAZ-AVI steady-state plasma level curves and the evolution of bacterial growth curves. The percentage of bacterial load reduction and the value of the recommended PK/PD indices have been taken into account to define the success or failure of the regimens. Probabilistic analysis was performed using Monte Carlo simulations of two populations: control and ICU. In both populations, dosing regimens endorsed for patients with CLcr higher than 10 mL/min reach the PK/PD indices recommended, T > MIC > 90% and Cmin/MIC > 1.3. While dosage regimens endorsed for patients with CLcr of 10 mL/min or lower fail (T > MIC < 60% and Cmin/MIC < 0.35). However, proposed dosing regimens based on shortening dosing intervals for these patients would be successful, increasing bacterial load reduction by almost 50% and reaching the proposed PK/PD indices. Therefore, CAZ-AVI dosing strategies based on model-informed precision dosing (MIPD) could directly influence the efficacy of results in ICU patients with renal insufficiency.

A descriptive pharmacokinetic/pharmacodynamic analysis of ceftazidime-avibactam in a case series of critically ill patients with augmented renal clearance

To describe the pharmacokinetics/pharmacodynamics (PK/PD) of a 2 h infusion of ceftazidime-avibactam (CAZ-AVI) in critically ill patients with augmented renal clearance (ARC). A retrospective review of all critically ill patients with ARC who were treated with CAZ-AVI between August 2020 and May 2023 was conducted. Patients whose 12-h creatinine clearance prior to CAZ-AVI treatment and steady-state concentration (Css) of CAZ-AVI were both monitored were enrolled. The free fraction (fCss) of CAZ-AVI was calculated from Css. The joint PK/PD targets of CAZ-AVI were considered optimal when a Css/minimum inhibitory concentration (MIC) ratio for CAZ ≥4 (equivalent to 100% fT > 4 MIC) and a Css/CT ratio of AVI >1 (equivalent to 100% fT > CT 4.0 mg/L) were reached simultaneously, quasioptimal when only one of the two targets was reached, and suboptimal when neither target was reached. The relationship between PK/PD goal achievement, microbial eradication and the clinical efficacy of CAZ-AVI was evaluated. Four patients were included. Only one patient achieved optimal joint PK/PD targets, while the other three reached suboptimal targets. The patient with optimal PK/PD targets achieved microbiological eradication, while the other three patients did not, but all four patients achieved good clinical efficacy. Standard dosages may not enable most critically ill patients with ARC to reach the optimal joint PK/PD targets of CAZ-AVI. Optimal drug dose adjustment of CAZ-AVI in ARC patients requires dynamic drug concentration monitoring.

Ceftazidime-avibactam induced renal disorders: past and present

With the increasing prevalence of multidrug-resistant Gram-negative bacterial pathogens worldwide, antimicrobial resistance has become a significant public health concern. Ceftazidime-avibactam (CAZ-AVI) exhibited excellent in vitro activity against many carbapenemase-producing pathogens, and was widely used for the treatment of various complicated infections. CAZ-AVI is well tolerated across all dosing regimens, and its associated acute kidney injury (AKI) in phase II/III clinical trials is rare. However, recent real-world studies have demonstrated that CAZ-AVI associated AKI was more frequent in real-world than in phase II and III clinical trials, particularly in patients receiving concomitant nephrotoxic agents, with critically ill patients being at a higher risk. Herein, we reviewed the safety data related to renal impairment of CAZ-AVI, and discussed its pharmacokinetic/pharmacodynamic targets and dosage adjustment in patients with impaired renal function. This review aimed to emphasize the importance for healthcare professionals to be aware of this adverse event of CAZ-AVI and provide practical insights into the dosage optimization in critically ill patients with renal dysfunction.

Therapeutic drug monitoring of ceftazidime/avibactam: why one leg is not enough to run

BACKGROUND

Therapeutic drug monitoring (TDM) is becoming an increasingly recommended approach for assessing optimal pharmacokinetic/pharmacodynamic (PK/PD) target attainment of ceftazidime/avibactam. Some authors hypothesized that the PK/PD target attainment of ceftazidime/avibactam could be assessed by means of the TDM of solely ceftazidime, since avibactam concentrations might be extrapolated based on the fixed 4:1 ceftazidime-to-avibactam ratio present in the vial. The reliability of this hypothesis could be called into question if a wide interindividual variability in the ceftazidime-to-avibactam ratio would exist among patients. This study aimed to assess the distribution of the individual ceftazidime-to-avibactam ratios in relation to renal function in a cohort of adult patients who were treated with continuous infusion ceftazidime/avibactam and underwent TDM of both ceftazidime and avibactam.

METHODS

Individual ceftazidime-to-avibactam ratio was calculated at each TDM assessment. Receiving operating characteristics (ROC) curve analysis was performed for testing the potential impact of renal function on ceftazidime-to-avibactam ratio variability.

RESULTS

A total of 188 TDM assessments were collected from 107 patients. The ceftazidime-to-avibactam ratios ranged from 1.29:1 to 13.46:1. Seventy-seven out of 188 ceftazidime-to-avibactam ratios (41.0%) were >5:1, and 36 (19.1%) were >6:1. Patients without renal dysfunction had significantly higher proportions of ceftazidime-to-avibactam ratio >5:1 (59.3% versus 23.8%; P < 0.001) and >6:1 (32.1% versus 6.3%; P < 0.001) compared with those with mild-to-severe renal dysfunction.

CONCLUSIONS

The findings may strengthen the contention that for properly assessing the PK/PD target attainment of ceftazidime/avibactam, both ceftazidime and avibactam concentrations should be measured, given the unpredictability of the ceftazidime-to-avibactam ratio occurring among patients.