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.