Population Pharmacokinetics of Cefuroxime in Critically Ill Patients Receiving Continuous Venovenous Hemofiltration With Regional Citrate Anticoagulation and a Phosphate-Containing Replacement Fluid

Clearance of Piperacillin-Tazobactam and Vancomycin During Continuous Renal Replacement With Regional Citrate Anticoagulation

BACKGROUND

The use of regional citrate anticoagulation during continuous venovenous hemodiafiltration (CVVHDF) has increased worldwide. However, data on its effect on the pharmacokinetics of antibiotics are limited. In this study, the authors aimed to measure the clearance of piperacillin-tazobactam and vancomycin in patients receiving CVVHDF with regional citrate anticoagulation.

METHODS

This study measured piperacillin-tazobactam and vancomycin concentrations in patients receiving CVVHDF with regional citrate anticoagulation. Dosing regimens were independently selected by intensivists. Arterial blood and effluent fluid samples were obtained over a single dosing interval and analyzed using ultra-high-performance liquid chromatography with tandem mass spectrometry.

RESULTS

Seventeen sampling intervals in 15 patients (9 receiving piperacillin-tazobactam only, 4 receiving vancomycin only, and 2 receiving both) were used. The median overall clearance for piperacillin was 35.2 mL/min [interquartile range (IQR): 32.2-38.6], 70 mL/min (IQR: 62.7-76.2) for tazobactam, and 29.5 mL/min (IQR: 26.2-32) for vancomycin.

CONCLUSIONS

This is the first study to quantify the pharmacokinetics of vancomycin and piperacillin-tazobactam in patients receiving CVVHDF with regional citrate anticoagulation. These results indicate high clearance and provide key information to guide optimal dosing.

Pharmacokinetics, Pharmacodynamics, and Dose Optimization of Cefiderocol during Continuous Renal Replacement Therapy

BACKGROUND

The need for continuous renal replacement therapy (CRRT) in critically ill patients with serious infections is associated with clinical failure, emergence of resistance, and excess mortality. These poor outcomes are attributable in large part to subtherapeutic antimicrobial exposure and failure to achieve target pharmacokinetic/pharmacodynamic (PK/PD) thresholds during CRRT. Cefiderocol is a novel siderophore cephalosporin with broad in vitro activity against resistant pathogens and is often used to treat critically ill patients, including those receiving CRRT, despite the lack of data to guide dosing in this population.

OBJECTIVE

The aim of this study was to evaluate the PK and PD of cefiderocol during in vitro and in vivo CRRT and provide optimal dosing recommendations.

METHODS

The PK and dialytic clearance of cefiderocol was evaluated via an established in vitro CRRT model across various modes, filter types, and effluent flow rates. These data were combined with in vivo PK data from nine patients receiving cefiderocol while receiving CRRT from phase III clinical trials. Optimal dosing regimens and their respective probability of target attainment (PTA) were assessed via an established population PK model with Bayesian estimation and 1000-subject Monte Carlo simulations at each effluent flow rate.

RESULTS

The overall mean sieving/saturation coefficient during in vitro CRRT was 0.90 across all modes, filter types, effluent flow rates, and points of replacement fluid dilution tested. Adsorption was negligible at 10.9%. Three-way analysis of variance (ANOVA) and multiple linear regression analyses demonstrated that effluent flow rate is the primary driver of clearance during CRRT and can be used to calculate optimal cefiderocol doses required to match the systemic exposure observed in patients with normal renal function. Bayesian estimation of these effluent flow rate-based optimal doses in nine patients receiving CRRT from the phase III clinical trials of cefiderocol revealed comparable mean (± standard deviation) area under the concentration-time curve values as patients with normal renal function (1709 ± 539 mg·h/L vs. 1494 ± 58.4 mg·h/L; p = 0.26). Monte Carlo simulations confirmed these doses achieved >90% PTA against minimum inhibitory concentrations ≤4 mg/L at effluent flow rates from 0.5 to 5 L/h.

CONCLUSION

The optimal dosing regimens developed from this work have been incorporated into the prescribing information for cefiderocol, making it the first and only antimicrobial with labeled dosing for CRRT. Future clinical studies are warranted to confirm the efficacy and safety of these regimens.

Pharmacokinetics and dialytic clearance of apixaban during in vitro continuous renal replacement therapy

Background

To evaluate the transmembrane clearance (CL_TM) of apixaban during modeled in vitro continuous renal replacement therapy (CRRT), assess protein binding and circuit adsorption, and provide initial dosing recommendations.

Methods

Apixaban was added to the CRRT circuit and serial pre-filter bovine blood samples were collected along with post-filter blood and effluent samples. All experiments were performed in duplicate using continuous veno-venous hemofiltration (CVVH) and hemodialysis (CVVHD) modes, with varying filter types, flow rates, and point of CVVH replacement fluid dilution. Concentrations of apixaban and urea were quantified via liquid chromatography-tandem mass spectrometry. Plasma pharmacokinetic parameters for apixaban were estimated via noncompartmental analysis. CL_TM was calculated via the estimated area under the curve (AUC) and by the product of the sieving/saturation coefficient (SC/SA) and flow rate. Two and three-way analysis of variance (ANOVA) models were built to assess the effects of mode, filter type, flow rate, and point of dilution on CL_TM by each method. Optimal doses were suggested by matching the AUC observed in vitro to the systemic exposure demonstrated in Phase 2/3 studies of apixaban. Linear regression was utilized to provide dosing estimations for flow rates from 0.5–5 L/h.

Results

Mean adsorption to the HF1400 and M150 filters differed significantly at 38 and 13%, respectively, while mean (± standard deviation, SD) percent protein binding was 70.81 ± 0.01%. Effect of CVVH point of dilution did not differ across filter types, although CL_TM was consistently significantly higher during CRRT with the HF1400 filter compared to the M150. The three-way ANOVA demonstrated improved fit when CL_TM values calculated by AUC were used (adjusted R² 0.87 vs. 0.52), and therefore, these values were used to generate optimal dosing recommendations. Linear regression revealed significant effects of filter type and flow rate on CL_TM by AUC, suggesting doses of 2.5–7.5 mg twice daily (BID) may be needed for flow rates ranging from 0.5–5 L/h, respectively.

Conclusion

For CRRT flow rates most commonly employed in clinical practice, the standard labeled 5 mg BID dose of apixaban is predicted to achieve target systemic exposure thresholds. The safety and efficacy of these proposed dosing regimens warrants further investigation in clinical studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-021-02248-7.

Cefuroxime pharmacokinetics and pharmacodynamics for intravenous dosage regimens with 750 mg or 1500 mg doses in healthy young volunteers

Introduction. Cefuroxime is an important antibiotic to treat several serious infections. Rapid elimination through the kidneys and the variation in MICs of various susceptible pathogens such as Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus and Streptococcus pneumoniae give rise to dosing issues, especially in otherwise healthy patients.

Aim. To investigate the probability of target attainment (PTA) for obtaining the optimal dosage regimens for cefuroxime in healthy young people.

Methodology. Two weeks apart 750 and 1500 mg cefuroxime were administered as an intravenous bolus to 20 healthy volunteers (mean age: 27 years). Population modelling and simulation studies were done based on the obtained data for cefuroxime plasma concentration.

Results. With a target value of time above MIC (T >MIC) greater than 50 % the simulations revealed that a PTA of >99 % is obtained for S. pneumoniae with a dosage regimen of 750 mg q12h. For E. coli and K. pneumoniae the PTA was <90 % even with the highest, simulated dosage of 1500 mg q6h. For S. aureus a dosage of 1500 mg q8h gave a PTA above 97 %.

Conclusions. S. pneumoniae is most likely treatable with a two-daily dose of 750 mg cefuroxime. Not treatable are K. pneumoniae and E. coli . For S. aureus 1500 mg q8h constitutes an optimal dosing schedule.

Quantification of total and unbound cefuroxime in plasma by ultra-performance liquid chromatography tandem mass spectrometry in a cohort of critically ill patients with hypoalbuminemia and renal failure

Background

Pharmacokinetic studies of cefuroxime by ultra‐performance liquid chromatography tandem mass spectrometry (UPLC‐MS/MS) have been limited to measurements of total concentrations. Here, we developed a robust method for quantifying total and unbound cefuroxime concentrations using UPLC‐MS/MS and ultrafiltration in critically ill patients with hypoalbuminemia and renal failure.

Methods

Method validation included accuracy, linearity, precision, repeatability, recovery, and limit of quantification (LOQ). Feasibility of the method was performed on samples obtained from randomly selected intensive care unit (ICU) patients. Total and unbound cefuroxime concentrations were quantified using UPLC‐MS/MS. Sampling times were categorized as trough (180‐1 min prior to administration), peak (10‐30 min after administration), mid (30‐360 min after administration), and continuous (sampling during administration). Pharmacokinetic/pharmacodynamic (PK/PD) targets were unbound cefuroxime concentrations above 4 times the minimum inhibitory concentration (32 mg/L).

Results

Intra‐assay and inter‐assay precision was <3%. Recovery was 99.7%‐100.3%, and LOQ was 0.1 mg/L. We included 11 patients (median age 72 years (range 54‐77). Median albumin serum concentrations and eGFR were 19 g/L (range 11‐40 g/L) and 48 mL/min/1.73 m² (range 7‐115 mL/min/1.73 m²), respectively. Median trough and mid concentrations of total cefuroxime were 22.27 mg/L (range 5.42‐54.03 mg/L) and 71.49 mg/L (range 53.87‐73.86 mg/L), and median unbound fraction was 75.42% (range 27.36%‐99.75%). Median unbound cefuroxime concentrations were 11.94 mg/L (range 3.85‐32.39 mg/L) (trough) and 55.62 mg/L (range 10.03‐62.62 mg/L) (mid).

Conclusion

The method is precise and accurate according to ISO 15189 and within the clinical range of cefuroxime (0.5‐100 mg/L). The method was applied in ICU patients and is suitable for TDM on unbound cefuroxime concentrations.

Population Pharmacokinetic Model-Based Evaluation of Standard Dosing Regimens for Cefuroxime Used in Coronary Artery Bypass Graft Surgery with Cardiopulmonary Bypass

The purpose of this study was to investigate the population pharmacokinetics (PK) of cefuroxime in patients undergoing coronary artery bypass graft (CABG) surgery. In this observational pharmacokinetic study, multiple blood samples were collected over a 48-h interval of intravenous cefuroxime administration. The samples were analyzed by using a validated high-performance liquid chromatography (HPLC) method. Population pharmacokinetic models were developed using Monolix (version 4.4) software. Pharmacokinetic-pharmacodynamic (PD) simulations were performed to explore the ability of different dosage regimens to achieve the pharmacodynamic targets. A total of 468 blood samples from 78 patients were analyzed. The PK for cefuroxime were best described by a two-compartment model with between-subject variability on clearance, the volume of distribution of the central compartment, and the volume of distribution of the peripheral compartment. The clearance of cefuroxime was related to creatinine clearance (CL_CR). Dosing simulations showed that standard dosing regimens of 1.5 g could achieve the PK-PD target of the percentage of the time that the free concentration is maintained above the MIC during a dosing interval (fT_MIC) of 65% for an MIC of 8 mg/liter in patients with a CL_CR of 30, 60, or 90 ml/min, whereas this dosing regimen failed to achieve the PK-PD target in patients with a CL_CR of ≥125 ml/min. In conclusion, administration of standard doses of 1.5 g three times daily provided adequate antibiotic prophylaxis in patients undergoing CABG surgery. Lower doses failed to achieve the PK-PD target. Patients with high CL_CR values required either higher doses or shorter intervals of cefuroxime dosing. On the other hand, lower doses (1 g three times daily) produced adequate target attainment for patients with low CL_CR values (≤30 ml/min).