title: Linezolid disposition after standard dosages in critically ill patients undergoing continuous venovenous hemofiltration: a report of 2 cases.
abstract: Linezolid is a new oxazolidinone antibiotic active against most Gram-positive microorganisms the renal elimination of which accounts for about 30% to 35% of all the clearance. Its pharmacokinetic ability was assessed during continuous venovenous hemofiltration (CVVH) in 2 anuric patients with severe postsurgical intraabdominal infections who were receiving standard dosages (600 mg intravenously twice a day). Blood samples for quantification of linezolid in plasma and in filtrate were collected after more than 4 days of therapy before dosing and at 0, 0.5, 1, 2, 3, 5, 7, 9, and 11 hours after the morning 1-hour intravenous infusion, and concentrations were determined by means of high-performance liquid chromatography. Linezolid was partially cleared by CVVH in both the patients (hemofiltration clearance [CL CVVH ] = 0.38 and 0.35 mL/min/kg), with high sieving coefficient values (0.76 to 0.92). Efficacious plasma exposure for time-dependent antibacterial activity of linezolid, either in terms of trough levels above minimum inhibitory concentration (MIC) at which 90% of the isolates are inhibited (Cmin >MIC90 ) or of area under the plasma concentration time curve to MIC90 ratio (AUC/MIC90 ) >100 hours, was ensured during CVVH in both patients. However, despite similar CL CVVH , significant interindividual pharmacokinetic variability was found in the 2 patients (AUC during the observational period [AUC 0-tau ] 334.71 versus 109.34 mg/L x h), mainly owing to substantial differences in non-CVVH-related clearance of linezolid (total CL, 0.55 versus 1.21 mL/min/kg). Our findings indicate that linezolid, although partially removed, does not warrant dosage modification during the first 48 hours when CVVH (with polysulfide hemofilter) at standard 2,000 mL/h substitution flow rate in predilution is applied to anuric patients. Thereafter, this choice is a reasonable one with the exception of those patients who have other features of linezolid toxicity and in which non-CVVH-related clearance might be impaired, although further evaluations are warranted.
authors.affiliation: Institute of Clinical Pharmacology and Toxicology, Department of Experimental and Clinical Pathology and Medicine, Medical School, University of Udine, Udine, Italy. federico.pea@med.uniud.it
authors.forename: Federico
authors.initials: F
authors.lastname: Pea
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Viale
authors.forename: Manuela
authors.initials: M
authors.lastname: Lugano
authors.forename: Federica
authors.initials: F
authors.lastname: Pavan
authors.forename: Luigia
authors.initials: L
authors.lastname: Scudeller
authors.forename: Giorgio
authors.initials: G
authors.lastname: Della Rocca
authors.forename: Mario
authors.initials: M
authors.lastname: Furlanut
mesh_terms: D000081:Acetamides / Q000008:administration & dosage* / Q000627:therapeutic use; D000368:Aged; D004334:Drug Administration Schedule; D016908:Gram-Positive Bacterial Infections / Q000188:drug therapy; D006440:Hemofiltration / Q000379:methods*; D006801:Humans; D007262:Infusions, Intravenous; D007676:Kidney Failure, Chronic / Q000628:therapy; D000069349:Linezolid; D008297:Male; D008875:Middle Aged; D023303:Oxazolidinones / Q000008:administration & dosage* / Q000627:therapeutic use; D010538:Peritonitis / Q000188:drug therapy; D013530:Surgical Wound Infection / Q000188:drug therapy
chemical_list: D000081:Acetamides; D023303:Oxazolidinones; D000069349:Linezolid