title: Population pharmacokinetics of ceftriaxone and pharmacodynamic considerations in haemodialysed patients.
abstract: OBJECTIVE
  To determine the pharmacokinetic parameters of ceftriaxone following an infusion in haemodialysed outpatients and to use these parameters for an optimisation of dosing based on pharmacodynamic indices.
  
  
  METHODS
  Fifty haemodialysed patients were enrolled in a single-centre, prospective, open-label study. They received short intravenous infusions of ceftriaxone 1 or 2 g every 48 hours for bronchopneumonia immediately after the dialysis session. Total plasma concentrations of ceftriaxone were analysed with a population pharmacokinetic approach using nonlinear mixed-effects modelling. Free drug concentrations were derived from published binding parameters in order to estimate the time when they exceed the minimum inhibitory concentration (MIC).
  
  
  RESULTS
  The pharmacokinetics were best described by a two-compartment model. None of the covariates tested (age, bodyweight, height, sex, body mass index, albumin) influenced the pharmacokinetic parameters. The estimated population pharmacokinetic parameters (interindividual variability [percentage of coefficient of variation]) were clearance 0.36 L/h (48%), volume of distribution of the central compartment 4.53 L (47%), intercompartmental clearance 10.8 L/h and volume of distribution of the peripheral compartment 9.54 L (63%). The terminal elimination half-life (t(1/2)beta) from plasma was 27.5 hours. The mean (range) times when the free drug concentration exceeded the MIC (T>MIC) following ceftriaxone 1 g infusion were 60.3 (53.0-67.7) hours and 2.5 (1.0-3.9) hours for the breakpoints 1 and 8 mg/L (based on free drug concentration), respectively. After administration of ceftriaxone 2 g, the T>MIC was 88.5 (78.8-98.3) hours and 17.7 (13.3-22.0) hours for the breakpoints 1 and 8 mg/L, respectively. The simulated free drug concentrations (median, first and third quartile) for 48 and 72 hours following the first dose of ceftriaxone 1g were 1.11, 0.63 and 1.89 mg/L, and 0.63, 0.28 and 1.18 mg/L, respectively. For ceftriaxone 2g infusion, the simulated free concentrations (median, first and third quartile) at 48 and 72 hours were 2.50, 1.40 and 4.52 mg/L, and 1.37, 0.60 and 2.70 mg/L, respectively.
  
  
  CONCLUSIONS
  On the basis of decreased clearance in haemodialysed patients, it can be argued that the dose of ceftriaxone should be decreased or the delay between doses should be increased. However, taking into account pharmacodynamic considerations, this study showed that following intravenous administration of ceftriaxone 1 g after each dialysis session, some patients were at risk of achieving a concentration below the MIC (1 mg/L), particularly if the second administration occurred 72 hours after the first dosing. Thus, a dose of ceftriaxone 2 g intravenously is recommended immediately following dialysis, particularly in patients with severe infections or when the dosing interval will be higher than 48 hours.
authors.affiliation: Department of Pharmacology, CHU Timone Marseille, University of Méditerranée, Marseille, France. nicolas.simon@medecine.univ-mrs.fr
authors.forename: Nicolas
authors.initials: N
authors.lastname: Simon
authors.forename: Bertrand
authors.initials: B
authors.lastname: Dussol
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Sampol
authors.forename: Raj
authors.initials: R
authors.lastname: Purgus
authors.forename: Philippe
authors.initials: P
authors.lastname: Brunet
authors.forename: Bruno
authors.initials: B
authors.lastname: Lacarelle
authors.forename: Yvon
authors.initials: Y
authors.lastname: Berland
authors.forename: Bernard
authors.initials: B
authors.lastname: Bruguerolle
authors.forename: Saïk
authors.initials: S
authors.lastname: Urien
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D001996:Bronchopneumonia / Q000188:drug therapy / Q000378:metabolism; D002443:Ceftriaxone / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000188:drug therapy / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D006435:Renal Dialysis
chemical_list: D000900:Anti-Bacterial Agents; D002443:Ceftriaxone