Pharmacokinetics of Small Spectrum Beta-lactam Antibiotics (Amoxicillin/Clavulanic Acid and Cefuroxime) in Patients on Intensive Care Units

Adequate antibiotic therapy is very important in the treatment of infections. Spectrum and dosing of the antibiotics are two factors of the therapy: the spectrum of an antibiotic can't be changed, but the dosing scheme can be optimized. Recent studies proved that an optimized dosing scheme can improve the efficacy of the treatment. Broad-spectrum antibiotics have unpredictable pharmacokinetics in patients on intensive care units. This is due to the pathophysiologic processes in the patients on intensive care units: increased distribution volume, hypoproteinemia, organ failure... The investigators guess that similar processes influence the pharmacokinetics of small spectrum antibiotics (like amoxicillin and cefuroxime), but data lacks. Because the pharmacokinetics of broad spectrum antibiotics in seriously ill patients are better known, physicians are more confident prescribing these drugs. Studying the pharmacokinetic interactions of small spectrum antibiotics in seriously ill patients, can help to give the physician the confidence to prescribe these small-spectrum antibiotics.

In this study, the investigators will study the pharmacokinetics of amoxicillin/clavulanic acid and cefuroxime, in 60 patients on intensive care. 8 blood samples will be drawn via a central catheter on different moments after one administration of the antibiotic in the steady state phase. All the patients are prescribed the antibiotics for the treatment of their infections: they get the antibiotic therapy anyway. By measuring the concentrations on different moments after one administration, the investigators can reconstruct the pharmacokinetic function.