Abstract: Objective To analyze the dosage of linezolid in severe patients with sepsis and acute kidney injury, optimize treatment plans, and to provide a reference for clinical medications. Methods Twenty-three patients with sepsis complicated with acute kidney injury who were treated with linezolid in the intensive care unit (ICU) of a hospital between May 1, 2022 and August 31, 2023 were selected. The test results of serum drug concentrations of these patients after intravenous administration were retrospectively analyzed while the pharmacokinetic parameters of linezolid were calculated. Monte Carlo simulation was used to calculate the probability target attainment (PTA) and cumulative fraction of response (CFR) of the current administration regimen (600 mg, q12h) against different gram-positive (G⁺) bacteria [Staphylococcus aureus, Streptococcus pneumoniae, Staphylococcus epidermidis, methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus faecalis, Enterococcus faecium]. The efficacy of the administration regimen was evaluated in terms of bacterial clearance. Results Among patients with sepsis complicated with acute kidney injury, the administration regimen was linzolid (600 mg, q12h). At the minimum inhibitory concentration (MIC) of 2 mg·L^-1 or less, this regimen could deliver satisfactory antibacterial effect (PTA=100%) against Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Enterococcus faecium and Streptococcus pneumoniae. The CFR was 95.42%, 92.03%, 93.15%, 91.45% and 98.81%, respectively. However, the antibacterial effect against MRSA was undesirable in that the PTA was less than 90%) and the CFR was no more than 49.45%. The steady-state minimum plasma concentration ( ) of linezolid was negatively correlated with platelet counts at 7 d after covariate medication. Conclusion During the intravenous treatment of Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Enterococcus faecium and Streptococcus pneumoniae in patients with sepsis and acute kidney injury, the regimen of 600 mg, q12h can produce good antibacterial effect when the MIC is less than 2 mg·L^-1. The dose can be appropriately reduced or the interval extended for such patients. However, the antibacterial effect of linezolid against MRSA is not so good, so the dose can be increased accordingly. The risk of thrombocytopenia increases after 7 days of medication with linezolid 600 mg, q12h. The dosage can be adjusted according to the serum drug concentration to ensure the antibacterial effect.

Key words: Linezolid, Sepsis, Monte Carlo Simulation, Intravenous Administration, Gram-Positive Cocci