{
  "abstract": "Background and Importance Therapeutic drug monitoring (TDM) is essential for antibiotics with a narrow therapeutic window, such as linezolid, where subtherapeutic exposure may compromise efficacy and overdosing increases the risk of haematological toxicity. Considerable interindividual variability in plasma trough concentrations (Cmin) has been described with standard dosing regimens. Understanding this variability is crucial for optimising dosing strategies and ensuring both efficacy and safety.Aim and Objectives To analyse the pharmacokinetics and interindividual variability of linezolid in hospitalised adults and to evaluate the impact of pharmacokinetic monitoring on dose adjustment and haematological safety.Material and Methods An observational, descriptive, retrospective study was conducted in a tertiary hospital including all adult patients treated with linezolid from June 2023 to February 2025. Demographic, clinical and analytical data were collected: sex, age, weight, height, serum creatinine (Cr), creatinine clearance (ClCr), treatment indication (empirical/targeted), route of administration, initial dosing regimen and Cmin levels. Plasma concentrations were determined in the Pharmacy Department using ARK enzyme immunoassay, with a therapeutic range of 2–10 µg/mL. Pharmacokinetic parameters—volume of distribution (Vd), clearance (Cl) and elimination constant (Ke)–were estimated using a one-compartment Bayesian model (PKS ). Continuous variables were expressed as mean ± SD, and categorical variables as frequencies and percentages.Results Twenty-nine patients were included (75.8% male, mean age 55 ±15 years). Mean weight was 78.3 ±16.8 kg, height 172.5 ±7.9 cm, Cr 1.19 ±1.34 mg/dL and ClCr 54.7 ±3.7 mL/min; 86% were in intensive care. Linezolid was administered intravenously, initially at 600 mg/12h in 79.3% of patients. Estimated pharmacokinetic parameters were: Vd 30.4 ±3.7 L/70 kg, Cl 2.6 ±0.3 L/h/70 kg and Ke 0.084 h − 1. Mean Cmin was 3.55 ±4.28 µg/mL; 62.1% were within the therapeutic range, 31% below and 6.9% above. Haematological toxicity occurred in 49.3% of patients. Dose adjustments were recommended in 34.5% of cases, achieving optimal concentrations in 82.7% after modification.Conclusion and Relevance Linezolid exhibits high interindividual pharmacokinetic variability, often resulting in sub-therapeutic exposures at standard dosing. Pharmacokinetic monitoring allows for individualised dose optimisation, maintaining concentrations within the therapeutic range and potentially improving safety and efficacy.Conflict of Interest No conflict of interest",
  "authors": [
    {
      "affiliations": [
        "Hospital Universitario Y Politécnico La Fe, Pharmacokinetics, Valencia, Spain"
      ],
      "name": "A Martínez Azor"
    },
    {
      "affiliations": [
        "Hospital Universitario Y Politécnico La Fe, Pharmacokinetics, Valencia, Spain"
      ],
      "name": "ME Beltran Bellvis"
    },
    {
      "affiliations": [
        "Hospital Universitario Y Politécnico La Fe, Pharmacokinetics, Valencia, Spain"
      ],
      "name": "MR Marqués Miñana"
    },
    {
      "affiliations": [
        "Hospital Universitario Y Politécnico La Fe, Intensive Care Unit, Valencia, Spain"
      ],
      "name": "M Martin Cerezuela"
    },
    {
      "affiliations": [
        "Hospital Universitario Y Politécnico La Fe, Head of Service, Valencia, Spain"
      ],
      "name": "J Garcia Pellicer"
    },
    {
      "affiliations": [
        "Hospital Universitario Y Politécnico La Fe, Hospital Manager, Valencia, Spain"
      ],
      "name": "JL Poveda Andrés"
    }
  ],
  "title": "4CPS-127 Pharmacokinetic monitoring and characterisation of linezolid in hospitalised patients",
  "uid": "adfb3a9e-cb4b-5ac8-a8b0-e36bc89e0fa8"
}