Pharmacokinetics of Linezolid in Children With Cystic Fibrosis

Patients with cystic fibrosis who have pulmonary exacerbations associated with the isolation of Methicillin-resistant Staphylococcus aureus (MRSA) in their sputum will be identified by their primary physicians and by laboratory record review. If they meet the inclusion criteria, they will be invited to participate in the study. The primary outcome variables include pharmacokinetic and pharmacodynamic indices. The study end points include completion of the sputum and blood sampling for pharmacokinetic studies of both intravenous and oral formulations of linezolid and collection of microbiologic specimen (sputum and anterior nares cultures) one month after discharge. Additionally, pharmacokinetic data will be analyzed for effects of age and cystic fibrosis transmembrane conductance regulator (CFTR) mutation on clearance of linezolid and for relationship between levels of linezolid achieved in sputum and blood and clinical outcome