Related Experiment Video
Updated: Jul 9, 2026

Multiplex Therapeutic Drug Monitoring by Isotope-dilution HPLC-MS/MS of Antibiotics in Critical Illnesses
Published on: August 30, 2018
Linezolid pharmacokinetic/pharmacodynamic profile in critically ill septic patients: intermittent versus continuous
Chiara Adembri1, Stefania Fallani, Maria Iris Cassetta
1Critical Care Department, Section of Anesthesiology and IC, University of Florence, Viale Morgagni 85, 50134 Firenze, Italy. chiara.adembri@unifi.it
Abstract:
Pharmacokinetics and pharmacodynamics are significantly altered in critically ill septic patients and the risk of prolonged periods with concentrations below the minimum inhibitory concentration (MIC) and of low area under the serum concentration-time curve/MIC (AUC/MIC) ratios is of concern. We compared the pharmacokinetic/pharmacodynamic (PK/PD) profile of linezolid administered by intermittent or continuous infusion in critically ill septic patients. Patients were divided into two groups: intermittent infusion (Group I) (600mg/12h); or continuous infusion (Group C) (300mg intravenous loading dose +900mg continuous infusion on Day 1, followed by 1200mg/daily from Day 2). Linezolid serum levels were monitored for 72h and microbiological data were collected. The clinical outcome was monitored. Sixteen patients completed the study. MICs of susceptible pathogens were 2mg/L for 80% of the isolates. In Group I, linezolid trough serum levels (C(min)) varied widely and were below the susceptibility breakpoint (4mg/L) during the study period; in 50% of patients C(min) was <1mg/L. In Group C, mean linezolid serum levels were more stable and, starting from 6h, were significantly higher than C(min) levels observed in Group I and were always above the susceptibility breakpoint. Time that the free drug concentration was above the MIC (T(free)>MIC) of>85% was more frequent in Group C than in Group I (P<0.05). Finally, with continuous infusion it was possible to achieve AUC/MIC values of 80-120 more frequently than with intermittent infusion (P<0.05). According to PK/PD parameters, continuous infusion has theoretical advantages over intermittent infusion in this population of patients.
Related Concept Videos
Drug Accumulation During Multiple Dosing: Intermittent IV Infusions
Determination of Multiple Dosing Parameters: Steady-State, Minimum and Maximum Concentrations
One-Compartment Model: IV Infusion
The one-compartment model for IV infusion uses mathematical equations to describe the rate of change in drug quantity in the body. At steady-state or infusion equilibrium, the drug input...
IV Infusion to Oral Dosing: Conversion Methods
Pharmacokinetic–Pharmacodynamic Relationship: Duration of Dose-Effect Relationship
Dosage Interval and Administration Route: Determination Methods