Evaluation of pharmacokinetic target attainment and hematological toxicity of linezolid in pediatric patients.

Background: Linezolid is commonly used to treat severe and/or resistant Gram-positive infections. Few studies have assessed its pharmacokinetic (PK) target attainment in pediatrics.

Objective: To evaluate the percentage of pediatrics achieving the PK targets of linezolid with standard dosing regimens and to assess the incidence and risk factors associated with its hematologic toxicity.

Methods: This prospective observational study included pediatric patients aged 0-14 who received linezolid for suspected or proven Gram-positive infections. Linezolid trough concentrations and the 24-h area under the curve (AUC₂₄) were estimated, and hematologic toxicity was assessed.

Results: Seventeen pediatric patients (5 neonates and 12 older pediatrics) were included. A wide variability was observed in linezolid's trough and AUC₂₄ (ranging from 0.5 to 14.4 mg/L and from 86 to 700 mg.h/L, respectively). The median AUC₂₄ was significantly higher in neonates than older pediatrics (436 [350-574] vs. 200 [134-272] mg,h/L, P = 0.01). Out of all patients, only 41% achieved adequate drug exposure (AUC₂₄ 160-300 mg.h/L and trough 2-7 mg/L), with 24% having subtherapeutic, and 35% having higher-than-optimal exposures. Hematological toxicity was observed in 53% of cases. Identified risk factors include treatment duration over 7 days, baseline platelet counts below 150 × 10⁹/L, sepsis/septic shock, and concomitant use of meropenem.

Conclusions: Linezolid's standard dosing failed to achieve its PK targets in approximately half of our pediatric cohort. Our findings highlight the complex interplay between the risk factors of linezolid-associated hematological toxicity and underscore the importance of its vigilant use and monitoring, particularly in pediatrics with concomitant multiple risk factors.