title: Levodopa therapy in Parkinson's disease: influence on liquid chromatographic tandem mass spectrometric-based measurements of plasma and urinary normetanephrine, metanephrine and methoxytyramine.
abstract: BACKGROUND
  Medication-related interferences with measurements of catecholamines and their metabolites represent important causes of false-positive results during diagnosis of phaeochromocytomas and paragangliomas (PPGLs). Such interferences are less troublesome with measurements by liquid chromatography with tandem mass-spectrometry (LC-MS/MS) than by other methods, but can still present problems for some drugs. Levodopa, the precursor for dopamine used in the treatment of Parkinson's disease, represents one potentially interfering medication.
  
  
  METHODS
  Plasma and urine samples, obtained from 20 Parkinsonian patients receiving levodopa, were analysed for concentrations of catecholamines and their O-methylated metabolites by LC-MS/MS. Results were compared with those from a group of 120 age-matched subjects and 18 patients with PPGLs.
  
  
  RESULTS
  Plasma and urinary free and deconjugated (free + conjugated) methoxytyramine, as well as urinary dopamine, showed 22- to 148-fold higher (P < 0.0001) concentrations in patients receiving levodopa than in the reference group. In contrast, plasma normetanephrine, urinary noradrenaline and urinary free and deconjugated normetanephrine concentrations were unaffected. Plasma free metanephrine, urinary adrenaline and urinary free and deconjugated metanephrine all showed higher (P < 0.05) concentrations in Parkinsonian patients than the reference group, but this was only a problem for adrenaline. Similar to normetanephrine, plasma and urinary metanephrine remained below the 97.5 percentiles of the reference group in almost all Parkinsonian patients.
  
  
  CONCLUSIONS
  These data establish that although levodopa treatment confounds identification of PPGLs that produce dopamine, the therapy is not a problem for use of LC-MS/MS measurements of plasma and urinary normetanephrine and metanephrine to diagnose more commonly encountered PPGLs that produce noradrenaline or adrenaline.
authors.affiliation: Institute of Clinical Chemistry and Laboratory Medicine, University of Dresden, Dresden, Germany.
authors.forename: Graeme
authors.initials: G
authors.lastname: Eisenhofer
authors.forename: Sebastian
authors.initials: S
authors.lastname: Brown
authors.forename: Mirko
authors.initials: M
authors.lastname: Peitzsch
authors.forename: Daniela
authors.initials: D
authors.lastname: Pelzel
authors.forename: Peter
authors.initials: P
authors.lastname: Lattke
authors.forename: Stephan
authors.initials: S
authors.lastname: Glöckner
authors.forename: Anthony
authors.initials: A
authors.lastname: Stell
authors.forename: Aleksander
authors.initials: A
authors.lastname: Prejbisz
authors.forename: Martin
authors.initials: M
authors.lastname: Fassnacht
authors.forename: Felix
authors.initials: F
authors.lastname: Beuschlein
authors.forename: Andrzej
authors.initials: A
authors.lastname: Januszewicz
authors.forename: Gabriele
authors.initials: G
authors.lastname: Siegert
authors.forename: Heinz
authors.initials: H
authors.lastname: Reichmann
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002853:Chromatography, Liquid; D004298:Dopamine / Q000031:analogs & derivatives / Q000097:blood / Q000652:urine; D004837:Epinephrine / Q000097:blood / Q000652:urine; D005260:Female; D006801:Humans; D007980:Levodopa / Q000008:administration & dosage* / Q000009:adverse effects; D008297:Male; D008676:Metanephrine / Q000097:blood / Q000652:urine; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood / Q000652:urine; D009647:Normetanephrine / Q000097:blood / Q000652:urine; D010235:Paraganglioma / Q000097:blood / Q000175:diagnosis* / Q000473:pathology / Q000652:urine; D010300:Parkinson Disease / Q000097:blood / Q000188:drug therapy* / Q000652:urine; D010673:Pheochromocytoma / Q000097:blood / Q000175:diagnosis* / Q000473:pathology / Q000652:urine; D053719:Tandem Mass Spectrometry
chemical_list: D009647:Normetanephrine; D007980:Levodopa; D008676:Metanephrine; C001746:3-methoxytyramine; D004298:Dopamine; D009638:Norepinephrine; D004837:Epinephrine
keywords: Levodopa; Parkinson’s disease; adrenaline; dopamine; mass spectrometry; metanephrine; methoxytyramine; noradrenaline; normetanephrine; paraganglioma; phaeochromocytoma