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Background and Importance Linezolid monitoring is crucial to prevent toxicity and optimise efficacy, especially in renal impairment. Implementing a pharmacokinetic protocol ensures standardised, individualised, and safer antibiotic therapy.Aim and Objectives Analysis of determinations after implementing a protocol for pharmacokinetic/pharmacodynamic (PK/PD) monitoring of linezolid.Material and Methods A 9 month ambispective study (12/1/2024–09/30/2025) included all patients with linezolid plasma level monitoring request.Variables collected in the study based on the recently implemented PK/PD protocol were: sex, age, indication, dosage, pharmacotherapeutic adjustments, and PK/PD parameters. Renal function was categorised as hyperfiltration (eGFR >100 mL/min) or impairment (eGFR <60 mL/min), and liver function was assessed via transaminases. Data were collected from Selene and Servilab, and analysed with Excel.The protocol, developed by the Hospital Pharmacy Department with the Clinical Analysis Department and reviewed by the Antimicrobial Stewardship Team (AST), recommends measuring a trough concentration after the third dose in patients with impaired renal or hepatic function or severe infections.Patient selection was performed by the pharmacokinetics pharmacist and the AST team. After determining plasma levels, dosing recommendations were provided through electronic health record, and pharmacokinetic analyses were conducted using MwPharm++ .Results Among 457 patients treated with linezolid, plasma levels were requested for 45. After excluding cases due to sampling errors, analytical issues, or pharmacy delays, 25 patients underwent pharmacokinetic monitoring. Of these, 80% were male, with a mean age of 72.5 years. Indications included skin and soft tissue infections (60%), respiratory (28%), and urinary (12%). Directed therapy represented 66.6% of cases, mainly targeting Staphylococcus aureus. The initial regimen was 600 mg every 12 hours, administered intravenously or orally.All monitored patients had alterations: 76% renal impairment, 8% haemodialysis, 8% augmented clearance, 8% hepatic impairment.Trough levels: 60% supratherapeutic, 37% within range, 3% subtherapeutic; AUC0–24/MIC below target in 16%, above in 50%.A total of 36 interventions were performed, all accepted: 50% discontinuation of therapy, 33.3% dose reduction to 600 mg every 24 h, and 16.6% maintenance of the original regimen.Conclusion and Relevance Linezolid plasma monitoring is essential in hospitalised patients, especially those with renal impairment. The high rate of supratherapeutic levels (63%) reflects reduced clearance in this population. PK/PD-guided dosing enables individualised therapy, improving antibiotic safety and effectiveness.Conflict of Interest No conflict of interest