title: Determinants of ceftriaxone clearance by continuous venovenous hemofiltration and hemodialysis.
abstract: OBJECTIVE
  To guide individual ceftriaxone dosages in patients receiving continuous renal replacement therapy.
  
  
  METHODS
  Prospective, outpatient study.
  
  
  METHODS
  University-affiliated general clinical research center.
  
  
  METHODS
  Eight patients receiving hemodialysis.
  
  
  METHODS
  We performed controlled clearance studies with three hemofilters: an acrylonitrile copolymer 0.6 m2 (AN69), polymethylmethacrylate 2.1 m2 (PMMA), and polysulfone 0.65 m2 (PS).
  
  
  RESULTS
  Subjects received ceftriaxone 1000 mg intravenously before the start of a clearance study. The concentration of ceftriaxone in multiple plasma and dialysate-ultrafiltrate samples was determined by high-performance liquid chromatography. The diffusional clearances (Cl(diffusion)) and sieving coefficients (SC) of ceftriaxone, urea, and creatinine were compared by a mixed-model repeated-measures analysis of variance with filter and blood, dialysate inflow, or ultrafiltration rate as the main effect and patient as a random effect. The fraction of ceftriaxone bound to plasma proteins was 43 +/- 15% (range 13-92%). Concentration dependence was evident in all three groups. The fraction unbound to plasma proteins (f(up)) at the time that SCs were determined was significantly lower in the PS group (0.16 +/- 0.07) than the AN69 group (0.30 +/- 0.17, p<0.01), but similar to that in the PMMA group (0.27 +/- 0.12). Despite the higher f(up), the SC of unbound ceftriaxone with the AN69 filter (0.48 +/- 0.13) was significantly lower than values for the PMMA (0.86 +/- 0.33) and PS (0.82 +/- 0.22) groups (p<0.05). Continuous venovenous hemofiltration clearance of urea and unbound ceftriaxone increased significantly only for the PMMA (p=0.006) and PS (p=0.015) filters when the ultrafiltration rate was increased. Significant linear relationships (p<0.0001) were observed between Cl(diffusion) of unbound ceftriaxone and clearance of urea for all three filters: AN69 slope = 0.57, PMMA slope = 0.90, and PS slope = 1.02. The slope of this relationship for the AN69 filter was significantly lower than for the other two filters.
  
  
  CONCLUSIONS
  Ceftriaxone clearance was significantly increased and membrane dependent during continuous venovenous hemofiltration and continuous venovenous hemodialysis. Thus individual ceftriaxone dosages for patients receiving continuous renal replacement therapies should incorporate extracorporeal clearance.
authors.affiliation: School of Medicine, University of Pittsburgh, Pennsylvania 15261, USA.
authors.forename: G R
authors.initials: GR
authors.lastname: Matzke
authors.forename: R F
authors.initials: RF
authors.lastname: Frye
authors.forename: M S
authors.initials: MS
authors.lastname: Joy
authors.forename: P M
authors.initials: PM
authors.lastname: Palevsky
mesh_terms: D000328:Adult; D000368:Aged; D002443:Ceftriaxone / Q000493:pharmacokinetics*; D002511:Cephalosporins / Q000493:pharmacokinetics*; D005260:Female; D006440:Hemofiltration; D006801:Humans; D008297:Male; D008567:Membranes, Artificial; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D011446:Prospective Studies; D006435:Renal Dialysis
chemical_list: D002511:Cephalosporins; D008567:Membranes, Artificial; D002443:Ceftriaxone