Linezolid, an antimicrobial widely used for infections caused by resistant Gram-positive bacteria, has been increasingly used in pediatrics and is considered an alternative to vancomycin, especially in cases of previous nephrotoxicity and therapeutic failure, in addition to the advantage of not requiring serum level monitoring. However, it is known for its hepatotoxicity, particularly with prolonged use. In our hospital, its use increased from February 2022 due to cost reduction and the consequent easing of prescribing restrictions. This preliminary observational study aimed to characterize the use of linezolid in pediatric patients at a university hospital in southern Brazil, evaluating indications and potential hepatotoxicity in this population.

We analyzed electronic medical records of 44 pediatric patients (0 to under 18 years old) who received linezolid between July 2024 and July 2025. We collected data on clinical indications, previous use of vancomycin, and evaluated liver function through AST and ALT levels before and after treatment. Patients with missing or incomplete data were excluded.

Among the 44 patients, 14 (31.81%) had not previously used vancomycin. Of these, 11 (78.57%) had no diagnosis of tuberculosis, being 10 (90.90%) oncology patients and 1 (9.09%) in the pediatric ICU. Among the 37 (84.09%) patients with AST and ALT recorded pre- and post-treatment, 15 (40.54%) and 13 (35.14%) showed AST and ALT variations, respectively, above the reference value for age.

Linezolid was used as a first-line or early alternative to vancomycin in high-complexity pediatric patients (oncologic, ICU) with non-tuberculous infections. Significant changes in liver function markers indicate that hepatotoxicity is a relevant adverse reaction, reinforcing the need for continuous monitoring and critical evaluation of the risk-benefit when using linezolid in pediatrics.