title: Determination of serum amantadine by liquid chromatography-tandem mass spectrometry.
abstract: BACKGROUND
  Amantadine (1-adamantylamine) is used for treatment of influenza, hepatitis C, parkinsonism, and multiple sclerosis. Current amantadine analysis by HPLC or gas chromatography (GC) requires a laborious sample pretreatment with extraction and/or derivatization steps. We established an LC-MS/MS method without protein precipitation, centrifugation, extraction and derivatization steps.
  
  
  METHODS
  50 microl sample+50 microl of 0.4 mg/l 1-(1-adamantyl)pyridinium bromide as internal standard+1000 microl water (96-well plate). Of this 25 microl+500 microl water (96-well plate; final serum dilution 1:462). LC-MS/MS: Surveyor MS pump, Autosampler, triple-quadrupole TSQ Quantum mass spectrometer (Thermo Electron). Autosampling: 2 microl of each sample. Chromatography: isocratic water/acetonitrile (60/40 v/v) with 5 g/l formic acid, flow rate 0.2 ml/min, run time 3 min, Phenomenex Luna C8(2) (100 x 2.0 mm (i.d.); 3-microm bead size) column. Mass spectrometry: electrospray atmospheric pressure ionization, positive ion and selective reaction monitoring mode, ion transitions m/z 152.0-->135.1 (at 22 eV amantadine) and 214.1-->135.1 (at 26 eV internal standard).
  
  
  RESULTS
  Calibration curves were constructed with spiked serum samples (amantadine 50-1000 microg/l, r>0.99). No carry over (5000 microg/l). No ion suppression with retention times similar to those of amantadine (1.8 min) and the internal standard (2.1 min). Detection limit 20 mg/l, linearity 20-5000 mg/l, intra-assay/inter-assay CV<6%/<8%, recovery 99-101%. Method comparison: LC-MS/MS=1.23 x GC-45 (Passing-Bablok regression). No significant bias between GC and LC-MS/MS (Bland-Altman plot).
  
  
  CONCLUSIONS
  We consider the sample pretreatment without deproteination, derivatization and centrifugation steps and the specificity of the tandem mass spectrometry as the most important points of our amantadine analysis method.
authors.affiliation: Bioscientia GmbH, Konrad-Adenauer-Strasse 17, D-55218 Ingelheim, Germany. torsten.arndt@bioscientia.de
authors.forename: Torsten
authors.initials: T
authors.lastname: Arndt
authors.forename: Brunhilde
authors.initials: B
authors.lastname: Guessregen
authors.forename: Axel
authors.initials: A
authors.lastname: Hohl
authors.forename: Janine
authors.initials: J
authors.lastname: Reis
mesh_terms: D000547:Amantadine / Q000097:blood*; D002138:Calibration; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D016903:Drug Monitoring; D006801:Humans; D012015:Reference Standards; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D000547:Amantadine