title: Quantification of the carbapenem antibiotic ertapenem in human plasma by a validated liquid chromatography-mass spectrometry method.
abstract: BACKGROUND
  Ertapenem (Invanz) is a newly developed carbapenem beta-lactam antibiotic. LC-MS is the method of choice for therapeutic drug monitoring (TDM) of a variety of drugs including antibiotics. No validated LC-MS method for ertapenem quantification is described in the literature so far.
  
  
  METHODS
  A rapid and robust LC-MS quantification method for ertapenem was developed and validated for clinical routine application in plasma samples. After immediate stabilisation with MES buffer (pH 6.5), samples were prepared for LC-MS analysis using simple protein precipitation. LC-MS coupling was realised by the use of a Phenomenex Synergi 4micro Polar-RP A80 Mercury LC column (10 x 2.0 mm) in combination with a Single-MS (Agilent 1100 LC-MSD SL) operating in negative selected ion monitoring (SIM) detection mode with ceftazidime as internal standard for adequate selective and sensitive analysis.
  
  
  RESULTS
  LC-MS method validation by means of determination of limit of detection (LOD 0.1 microg mL-1), lower limit of quantification (LLOQ 1 microg mL-1), linearity (0.1-50 microg mL-1), recovery (> 90%), intra- and inter-day precision (RSD < 10%), accuracy (> 90%), inter-subject variability (< 10% at LLOQ), drug stability in plasma (> 3 months) and in post-extracted samples (> 99% for 24 h), and matrix effects (process efficiency > 90%) showed excellent performance parameters considering Guidance for Industry - Bioanalytical Method Validation.
  
  
  CONCLUSIONS
  This method is perfectly appropriate for routine quantification of ertapenem and possibly other polar carbapenem beta-lactam antibiotics.
authors.affiliation: Hannover Medical School, Institute of Pharmacology, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany. koal.therese@mh-hannover.de
authors.forename: Therese
authors.initials: T
authors.lastname: Koal
authors.forename: Michael
authors.initials: M
authors.lastname: Deters
authors.forename: Klaus
authors.initials: K
authors.lastname: Resch
authors.forename: Volkhard
authors.initials: V
authors.lastname: Kaever
mesh_terms: D002138:Calibration; D015780:Carbapenems / Q000097:blood* / Q000493:pharmacokinetics / Q000592:standards; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004355:Drug Stability; D000077727:Ertapenem; D006801:Humans; D007676:Kidney Failure, Chronic / Q000378:metabolism; D013058:Mass Spectrometry / Q000379:methods*; D012015:Reference Standards; D015203:Reproducibility of Results; D047090:beta-Lactams / Q000097:blood* / Q000493:pharmacokinetics / Q000592:standards
chemical_list: D015780:Carbapenems; D047090:beta-Lactams; D000077727:Ertapenem