title: Stability of methylecgonidine and ecgonidine in sheep plasma in vitro.
abstract: BACKGROUND
  Crack smokers are exposed to a pyrolysis product, methylecgonidine (MEG), which can be used as an analytical marker for crack smoking. Ecgonidine (EC), a hydrolytic product of MEG, has been identified in urine of crack smokers. MEG undergoes conversion to EC, complicating analysis and perhaps explaining a lack of forensic blood specimens containing MEG.
  
  
  METHODS
  We developed gas chromatography-mass spectrometry (GC-MS) assays for MEG and EC. Plasma was collected from sheep blood containing 0, 0.06, or 0.24 mol/L (0%, 0.25%, or 1%) NaF. MEG was added to these plasmas, and they were incubated at -80, 1, 21, or 37 degrees C to determine whether there were temporal, temperature, or storage effects on MEG stability over 48 h.
  
  
  RESULTS
  Decreased temperature and increased NaF concentrations limited MEG degradation and EC formation. MEG stored in plasma at -80 degrees C was stable up to 1 month, even in the absence of NaF.
  
  
  CONCLUSIONS
  MEG is stable in sheep plasma collected in commercially available, evacuated blood-collection tubes containing NaF and stored at -80 degrees C. In vitro formation of EC can be minimized with appropriate sample handling, and its in vivo formation may provide a better marker of crack smoking than its parent pyrolysis product.
authors.affiliation: University of Rochester School of Medicine, Departments of Pathology and Laboratory Medicine, Rochester, NY 14642, USA.
authors.forename: K B
authors.initials: KB
authors.lastname: Scheidweiler
authors.forename: J
authors.initials: J
authors.lastname: Shojaie
authors.forename: M A
authors.initials: MA
authors.lastname: Plessinger
authors.forename: R W
authors.initials: RW
authors.lastname: Wood
authors.forename: T C
authors.initials: TC
authors.lastname: Kwong
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000097:blood; D003042:Cocaine / Q000031:analogs & derivatives* / Q000097:blood*; D004355:Drug Stability; D008401:Gas Chromatography-Mass Spectrometry; D012756:Sheep; D015813:Substance Abuse Detection / Q000379:methods*
chemical_list: D015415:Biomarkers; C068464:anhydroecgonine methyl ester; C120357:ecgonidine; D003042:Cocaine