Pharmacokinetics and Therapeutic Target Attainment of Meropenem in Pediatric Post-Liver Transplant Patients: Extended vs Intermittent Infusion

PURPOSE

The aim of this study is to characterize the concentration-time profile, pharmacokinetics parameters, and therapeutic target attainment of meropenem in pediatric post-liver transplant patients according to the duration of infusion.

METHODS

This is a prospective cohort of pediatric transplant recipients with preserved renal function receiving meropenem 40 mg/kg every 8 hours. The patients were stratified into 2 groups based on infusion duration: G1 (15 minutes of intermittent infusion) and G1 (3 hours of extended infusion). Two blood samples per child were collected during the same interval within 48 hours of starting the antimicrobial. Meropenem concentrations were determined by high-performance liquid chromatography with tandem mass spectrometry. Pharmacokinetic parameters were assessed using a noncompartmental analysis. The therapeutic target was defined as 100% of the time above the minimum inhibitory concentration.

FINDINGS

Fourteen patients with 28 measured meropenem concentrations were included. Lower values of volume of distribution and meropenem clearance compared with other critically ill pediatric populations were found. All patients achieved the therapeutic target against gram-negative pathogens with a minimum inhibitory concentration of ≤8 mg/L. Patients receiving a 15-minute infusion had higher values of peak and trough concentrations, resulting in unnecessary increased total drug exposure when compared to patients receiving a 3-hour infusion (P < .05).

CONCLUSIONS

Meropenem at 120 mg/kg/d attained the therapeutic target against sensitive microorganisms in pediatric liver transplant recipients. The extended infusion should be preferred for patient safety. Because of the pharmacokinetic changes resulting from liver transplantation, individualized meropenem dosing regimens may be necessary.

Pharmacokinetics and therapeutic target attainment of vancomycin in pediatric post-liver transplant patients

INTRODUCTION

Vancomycin is widely prescribed to treat or prevent Gram-positive infections in pediatric liver transplant recipients. The objective of this prospective cohort study is to describe vancomycin pharmacokinetics and to evaluate the therapeutic target attainment after initial dose regimen.

MATERIALS AND METHODS

Patients with previous renal injury were excluded. Vancomycin therapy started with 40‒60 mg/kg/day. The pharmacokinetic parameters were assessed using two steady-state blood samples and the first-order kinetic equations. Therapeutic target was defined as vancomycin 24-hour Area Under the Curve/Minimum Inhibitory Concentration (AUC/MIC) ≥ 400 and < 600.

RESULTS

Sixteen patients were included. The found vancomycin clearance, half-life, and volume of distribution were, respectively: 2.1 (1.3‒2.8) mL/kg/min, 3.3 (2.7‒4.4) hours, and 0.7 (0.5‒0.9) L/kg. With the initial dose, only 6 (37 %) patients reached the therapeutic target against Gram-positive pathogens with MIC 1 mg/L. After individual dose adjustments, all patients reached the target. The correlation between trough levels and AUC was low (R2 = 0.5).

CONCLUSIONS

Pediatric patients with preserved renal function after liver transplantation have an increased volume of distribution for vancomycin, and most patients present subtherapeutic levels after the standard initial dosing regimen. With the vancomycin AUC-guided monitoring and dosing, it is possible to improve therapeutic target attainment.

Synergistic combination of aztreonam and ceftazidime/avibactam against resistant Stenotrophomonas maltophilia on pancreatitis

INTRODUCTION

Stenotrophomonas maltophilia is a Gram-negative, opportunistic pathogen associated with a high morbidity and mortality rate. We report our clinical experience in treating a patient with infected pancreatic necrosis caused by multidrug-resistant (MDR) S. maltophilia with a novel drug combination.

CASE REPORT

A 65-year-old male with history of type II diabetes was admitted with acute pancreatitis, voluminous ascites, and signs of sepsis after undergoing an echo-endoscopy procedure with pancreas biopsy to investigate a Wirsung duct dilatation. Retroperitoneal fluid culture revealed S. maltophilia resistant to colistin and with intermediate susceptibility to trimethoprim-sulfamethoxazole and levofloxacin. The synergy between aztreonam (ATM) and ceftazidime/avibactam (CZA) was demonstrated using the combined disk pre-diffusion test.

CONCLUSIONS

There are sparse data providing guidance on the optimal regimen against MDR S. maltophilia infections. Although in this case a surgical excision was essential, combination of ATM and CZA provided effective synergistic antimicrobial treatment with clinical cure of severe acute pancreatitis infected with S. maltophilia. The combined disk pre-diffusion test with ATM and CZA requires no special equipment and can be routinely performed in clinical microbiology labs. Combination of ATM with CZA should be considered for cases of MDR S. maltophilia infections with limited treatment options.

Pharmacokinetic and pharmacodynamic considerations of antibiotics and antifungals in liver transplantation recipients

The liver plays a major role in drug metabolism. Liver transplantation impacts the intrinsic metabolic capability and extrahepatic mechanisms of drug disposition and elimination. Different levels of inflammation and oxidative stress during transplantation, the process of liver regeneration, and the characteristics of the graft alter the amount of functional hepatocytes and activity of liver enzymes. Binding of drugs to plasma proteins is affected by the hyperbilirubinemia status and abnormal synthesis of albumin and alpha-1-acid glycoproteins. Postoperative intensive care complications such as biliary, circulatory, and cardiac also impact drug distribution. Renally eliminated antimicrobials commonly present reduced clearance due to hepatorenal syndrome and the use of nephrotoxic immunosuppressants. In addition, liver transplantation recipients are particularly susceptible to multidrug-resistant infections due to frequent manipulation, multiple hospitalizations, invasive devices, and frequent use of empiric broad-spectrum therapy. The selection of appropriate anti-infective therapy must consider the pathophysiological changes after transplantation that impact the pharmacokinetics and pharmacodynamics of antibiotics and antifungal drugs.

Trough-Guided Versus AUC/MIC-Guided Vancomycin Monitoring: A Cost Analysis

PURPOSE

Recent vancomycin dosing and monitoring guidelines recommend monitoring vancomycin area under the 24-hour time-concentration curve instead of traditional trough-only monitoring. This study aimed to compare the total costs of vancomycin dosing and monitoring between trough-guided and AUC-guided approaches in a quaternary hospital from Brazil.

METHODS

In this retrospective cohort study, patients were divided into 2 groups according to the monitoring method. Patients with previous renal impairment were excluded. Vancomycin AUC was estimated by using 2 steady-state serum concentrations and first-order kinetics equations. The primary outcome was total cost of vancomycin therapy and monitoring from the hospital perspective, which included costs of cumulative doses, laboratory fees, materials used in blood collection, nursing time for collection, and pharmacist time for result interpretation.

FINDINGS

A total of 68 patients were included in the AUC/MIC-guided monitoring group, and 76 patients were included in the trough-guided monitoring group. There were no significant differences between groups regarding baseline serum creatinine level, duration of vancomycin therapy, and cumulative vancomycin dose. The median (interquartile range) total vancomycin drug and monitoring cost was $298.32 ($153.81-$429.85) for the AUC/MIC-guided group compared with $285.59 ($198.81-$435.57) for the trough-guided group (P = 0.9658).

IMPLICATIONS

Vancomycin AUC estimation using 2 steady-state serum concentrations and first-order kinetics equations is a feasible alternative for limited-resource institutions that intend to transition from a trough approach to AUC/MIC-guided monitoring. (Clin Ther. 2022;44:XXX-XXX) © 2022 Elsevier HS Journals, Inc.

Vancomycin area under the curve-guided monitoring in pediatric patients

OBJECTIVE

To assess the percentage of vancomycin area under the curve/minimum inhibitory concentration target attainment in pediatric patients after the empirical dose regimen and to demonstrate the applicability of this method for vancomycin monitoring.

METHODS

A retrospective cohort study was performed including pediatric patients with normal renal function admitted between January 2020 and December 2020. The one-compartment model with first-order kinetics was used to estimate the pharmacokinetic parameters, and the area under the curve was calculated by the trapezoidal rule. The therapeutic target was defined as area under the curve/minimum inhibitory concentration ≥ 400 and < 600. The Chi-squared test was applied to compare the percentage of target attainment over age groups, while the pharmacokinetic parameters were compared by the Kruskal-Wallis test with Dunn's test for post hoc analyses. We considered significant p-values < 0.05.

RESULTS

In total, 42 pairs of vancomycin levels were analyzed from 17 patients enrolled in this study. After empirical vancomycin daily dosing, the therapeutic target was achieved in five (29%) patients; four patients (24%) had a supratherapeutic initial area under the curve/minimum inhibitory concentration value (> 600mg.h/L), and eight (47%) patients had subtherapeutic values (< 400mg.h/L). The most identified pathogens were Staphylococcus spp. (n = 7). Trough levels and areas under the curve showed moderate correlation values (R2 = 0.73). Acute kidney injury occurred in one (6%) patient.

CONCLUSION

Most patients did not reach the therapeutic target with a vancomycin empirical dose regimen, and the implementation of area under the curve-based dosing using two sample measurements allowed for real-time dose adjustments based on individuals' pharmacokinetic parameters.

New perspectives of vancomycin monitoring

Vancomycin is an antibiotic mainly used to treat infections caused by gram-positive bacteria. Currently, the monitoring of vancomycin treatment is carried out through the trough of plasma concentration, but the new studies and recommendations suggest the use of the ratio between the area under the plasma concentration curve and the minimum inhibitory concentration of the bacterium (AUC/MIC) for monitoring patients, especially in pediatrics due to the high variability of pharmacokinetic parameters in this population. The AUC/MIC of vancomycin can be determined using Bayesian software or by the trapezoid method with similar results and only practical differences. Comparative studies between monitoring by AUC/MIC and trough levels have shown better results of efficacy and safety in the use of vancomycin in those groups monitored by AUC/MIC and corroborate with the new recommendations.

Vancomycin area under the curve-guided monitoring in pediatric patients

Objective:

To assess the percentage of vancomycin area under the curve/minimum inhibitory concentration target attainment in pediatric patients after the empirical dose regimen and to demonstrate the applicability of this method for vancomycin monitoring.

Methods:

A retrospective cohort study was performed including pediatric patients with normal renal function admitted between January 2020 and December 2020. The one-compartment model with first-order kinetics was used to estimate the pharmacokinetic parameters, and the area under the curve was calculated by the trapezoidal rule. The therapeutic target was defined as area under the curve/minimum inhibitory concentration ≥ 400 and < 600. The Chi-squared test was applied to compare the percentage of target attainment over age groups, while the pharmacokinetic parameters were compared by the Kruskal-Wallis test with Dunn’s test for post hoc analyses. We considered significant p-values < 0.05.

Results:

In total, 42 pairs of vancomycin levels were analyzed from 17 patients enrolled in this study. After empirical vancomycin daily dosing, the therapeutic target was achieved in five (29%) patients; four patients (24%) had a supratherapeutic initial area under the curve/minimum inhibitory concentration value (> 600mg.h/L), and eight (47%) patients had subtherapeutic values (< 400mg.h/L). The most identified pathogens were Staphylococcus spp. (n = 7). Trough levels and areas under the curve showed moderate correlation values (R² = 0.73). Acute kidney injury occurred in one (6%) patient.

Conclusion:

Most patients did not reach the therapeutic target with a vancomycin empirical dose regimen, and the implementation of area under the curve-based dosing using two sample measurements allowed for real-time dose adjustments based on individuals’ pharmacokinetic parameters.

Beta-Lactams Therapeutic Monitoring in Septic Children-What Target Are We Aiming for? A Scoping Review

The antimicrobial therapy of sepsis and septic shock should be individualized based on pharmacokinetic/pharmacodynamic (PK/PD) parameters to deliver effective and timely treatment of life-threatening infections. We conducted a literature scoping review to identify therapeutic targets of beta-lactam antibiotics in septic pediatric patients and the strategies that have been applied to overcome sepsis-related altered pharmacokinetics and increase target attainment against susceptible pathogens. A systematic search was conducted in the MEDLINE, EMBASE and Web of Science databases to select studies conducted since 2010 with therapeutic monitoring data of beta-lactams in septic children. Last searches were performed on 02 September 2021. Two independent authors selected the studies and extracted the data. A narrative and qualitative approach was used to summarize the findings. Out of the 118 identified articles, 21 met the eligibility criteria. Population pharmacokinetic modeling was performed in 12 studies, while nine studies reported data from bedside monitoring of beta-lactams. Most studies were conducted in the United States of America (n = 9) and France (n = 5) and reported PK/PD data of amoxicillin, ampicillin, azlocillin, aztreonam, cefazolin, cefepime, cefotaxime, ceftaroline, ceftazidime, doripenem, meropenem and piperacillin/tazobactam. Therapeutic targets ranged from to 40% fT> MIC to 100% fT> 6 × MIC. Prolonging the infusion time and frequency were most described strategies to increase target attainment. Monitoring beta-lactam serum concentrations in clinical practice may potentially maximize therapeutic target attainment. Further studies are required to define the therapeutic target associated with the best clinical outcomes.