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.

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.

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.

Vancomycin area under the curve-guided monitoring in pediatric patients. / Monitoramento orientado pela área sob a curva da vancomicina em pacientes pediátricos.

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.

OBJETIVO: Avaliar a probabilidade de atingir o alvo pela razão entre a área sob a curva e a concentração inibitória mínima de vancomicina em pacientes pediátricos após o esquema de dose empírica e demonstrar a aplicabilidade desse método para o monitoramento da vancomicina. METÓDOS: Foi realizado um estudo de coorte retrospectivo que incluiu pacientes pediátricos com função renal normal internados entre janeiro e dezembro de 2020. O modelo de um compartimento com cinética de primeira ordem foi utilizado para estimar os parâmetros farmacocinéticos, e a área sob a curva foi calculada pela regra do trapézio. O alvo terapêutico foi definido como a razão entre a área sob a curva e a concentração inibitória mínima ≥ 400 e < 600. O teste do qui-quadrado foi aplicado para comparar a probabilidade de atingir o alvo nos grupos etários, enquanto os parâmetros farmacocinéticos foram comparados pelo teste de Kruskal-Wallis com o teste de Dunn para análises post hoc. Consideraram-se significativos os valores de p < 0,05. RESULTADOS: Foram analisados, no total, 42 pares de níveis de vancomicina de 17 pacientes inscritos neste estudo. Após a dose diária empírica de vancomicina, o alvo terapêutico foi atingido em cinco (29%) pacientes; quatro pacientes (24%) apresentavam razão entre a área sob a curva inicial supraterapêutica e o valor de concentração inibitória mínima (> 600mg.h/L) e oito (47%) tinham valores subterapêuticos (< 400mg.h/L). Os patógenos mais identificados foram Staphylococcus spp. (n = 7). Os níveis de vale e as áreas sob a curva mostraram valores moderados de correlação (R2 = 0,73). Um (6%) paciente apresentou lesão renal aguda. CONCLUSÃO: A maioria dos pacientes não atingiu o alvo terapêutico com esquema de dose empírica de vancomicina, e a implementação de dosagem baseada na área sob a curva usando duas medições de amostra permitiu ajustes de dose em tempo real com base nos parâmetros farmacocinéticos dos indivíduos.

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.