Pharmacokinetic and Pharmacodynamic Evaluation of Linezolid Administered Intravenously in MRSA-positive, Morbidly Obese Patients With Pneumonia

The objectives of the study are: (i) to evaluate the proportion of patients who attain a T\>MIC (Minimum Inhibitory Concentration) of 100% and the time frame in which they do so. The investigators therefore plan to measure unbound linezolid trough concentrations before administration of the second, third, fourth and fifth dose. Furthermore, the investigators will assess the AUC0 - 24h/MIC in all study subjects. Therefore, multiple plasma samples will be drawn after the fourth or fifth dose, when steady state conditions are reached. (ii) to describe the pharmacokinetic variability of unbound linezolid concentrations in this cohort using a population pharmacokinetic model and to assess the expected probability of target attainment (PTA) by MIC against MRSA. Twenty adult, MRSA-positive, morbidly obese patients with clinically and radiologically documented pneumonia are to be included. Therefore, a multi-centre, international observational study is necessary. Given the specific target population this study is not feasible in a single-centre approach. The goal is to find up to 6 centres that anticipate including 3 to 4 patients in the study within a time frame of one year. Included patients should receive at least 6 doses of linezolid. Linezolid must be administered intravenously (iv) over a one hour controlled infusion (with use of a volumetric infusion pump).