Serum and sputum concentrations following the oral administration of linezolid in adult patients with cystic fibrosis

Objectives: Linezolid is a new oxazolidinone antibiotic with efficacy against a broad range of Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). In this study, we have determined the serum and sputum linezolid concentrations in adults with cystic fibrosis (CF) following oral drug administration. Methods: Eleven adult patients with CF were recruited. Subjects received 600 mg of linezolid orally every 12 h for a total of six doses. Serum and sputum levels were measured just before and at 2 h after the final dose of linezolid. A further serum level was measured at 4 h. Results: Ten adult patients completed the study. Mean (S.D.) serum linezolid concentrations were 2.3 mglL (1.5) at 12 h following the fifth dose. At 2 and 4 h following the sixth dose, concentrations were 13.5 (4.3) and 8.1 (3.3). Mean (S.D.) linezolid sputum concentrations were 3.6 (2.1) and 17.4 (7.2) mglL at 0 and 2 h following drug administration. Conclusions: The oral administration of linezolid results in good sputum penetration in patients with CF. Mean levels exceed the required MIC for the treatment of MRSA for >80% of the dosing period for serum and the majority of the dosing period for sputum.