Pharmacokinetic Analysis

This observational study will characterize the pharmacokinetics of linezolid in young infants. Participants will receive linezolid either as part of routine clinical care or as a single, one-time study dose. Blood samples collected following linezolid administration will be used to measure drug concentrations and describe how linezolid is absorbed, distributed, metabolized, and eliminated in this population. Clinical information, including demographic characteristics, laboratory values, and treatment details, will also be collected. The results will be used to develop pharmacokinetic models to improve linezolid dosing recommendations and support precision dosing in young infants.

This prospective single-center observational pharmacokinetic study will evaluate plasma levobupivacaine concentrations after ultrasound-guided transversus abdominis plane (TAP) block in adult patients undergoing elective abdominal surgery under general anesthesia at CHU Liège. Participants receiving TAP block as part of standard clinical care (levobupivacaine 0.375%, total volume 40 mL, maximum dose 150 mg) will undergo serial blood sampling at 3, 7, 15, 30, 60, 120, and 180 minutes after block completion. Plasma levobupivacaine concentrations will be measured using validated LC-MS/MS methods. The primary objectives are to estimate maximum plasma concentration (Cmax) and time to maximum concentration (Tmax). Secondary objectives include characterization of the concentration-time profile, AUC0-180, interindividual variability, and exploratory associations with clinical factors (age, sex, BMI, type of surgery). The study also aims to inform a pragmatic safety window for subsequent intravenous lidocaine infusion used in multimodal analgesia protocols. Approximately 26 participants will be enrolled. No modification of routine anesthesia or analgesic care is required apart from study-related blood sampling.