The purpose of this study is to investigate the pharmacokinetic properties in critically ill patients of a few of the most used antimicrobial drugs (amikacin, linezolid, meropenem, piperacillin/tazobactam, vancomycin). The primary objective is the identification of the clinical parameters affecting the kinetics of these drugs and the study of the contribution of extracorporeal depuration techniques to the elimination of these molecules. The secondary objective is to describe and compare the therapeutic therapies adopted in the Intensive Care Units participating in the project.

For each molecule, the study will involve 300 patients admitted to Intensive Care Units. For each patient five blood samples will be collected on average, in order to measure drug plasma concentrations. Patient clinical conditions will be collected through an electronic clinical record. Finally, on the basis of those data, pharmacokinetic models will be developed to describe the evolution in time of drug plasma concentrations.

Inclusion Criteria:

• patients undergoing antibiotic therapy with amikacin, linezolid, meropenem, piperacillin/tazobactam, or vancomycin.
• patients whose antibiotic therapy started during the stay in ICU or less than 24h before admission to ICU.
• patients with anticipated length of stay in ICU of at least 24h.
• patients with already-placed catheter

Exclusion Criteria:

• patients undergoing antibiotic prophylaxis
• lack of informed consent

Patients admitted to Intensive Care Unit (ICU)