title: Stability of pain-related medications, metabolites, and illicit substances in urine.
abstract: BACKGROUND
  Effective urine drug testing requires an understanding of the stability of medications, metabolites and other substances excreted in the urine matrix. When the testing results do not fit the clinical picture, physicians frequently request repeat testing of the original specimen in order to corroborate the results. We determined the stability in urine of various medications, metabolites, and illicit substances commonly requested for testing by physicians treating patients with pain and pain-related disorders.
  
  
  METHODS
  Quantitative analyses of urine specimens were performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Two replicates at a high and low concentration were analyzed at time 0, and after 2, 3 and 6 months following storage at +4 °C and -20 °C. At each time interval, the percent difference from time 0 for each analyte was calculated and averaged for each storage condition.
  
  
  RESULTS
  For the majority of medications, the percent differences were within 20% of the original measurement for all 3 storage conditions. All were within 30% of the original measurement after 2, 3 and 6 months in all storage conditions, except for 7-amino-clonazepam, and carboxy-tetrahydrocannabinol.
  
  
  CONCLUSIONS
  The findings from the current study confirm that the majority of medications, metabolites, and illicit substances commonly requested for testing by physicians treating patients with pain and pain-related disorders are stable within 20% of the original concentration when stored refrigerated or frozen for up to 6 months. Thus, delayed testing, repeat testing, and add-on testing of urine specimens can yield reliable results for up to 6 months following the urine collection date.
authors.affiliation: Millennium Research Institute, 16980 Via Tazon, San Diego, CA 92127, USA. egonzales@millenniumlabs.com
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Gonzales
authors.forename: Gary
authors.initials: G
authors.lastname: Ng
authors.forename: Amadeo
authors.initials: A
authors.lastname: Pesce
authors.forename: Cameron
authors.initials: C
authors.lastname: West
authors.forename: Robert
authors.initials: R
authors.lastname: West
authors.forename: Charles
authors.initials: C
authors.lastname: Mikel
authors.forename: Sergey
authors.initials: S
authors.lastname: Latyshev
authors.forename: Perla
authors.initials: P
authors.lastname: Almazan
mesh_terms: D000661:Amphetamine / Q000378:metabolism / Q000652:urine; D000700:Analgesics / Q000737:chemistry / Q000652:urine*; D002853:Chromatography, Liquid / Q000592:standards; D004355:Drug Stability; D003932:Heroin / Q000378:metabolism / Q000652:urine; D006801:Humans; D013287:Illicit Drugs / Q000378:metabolism / Q000652:urine*; D009020:Morphine / Q000378:metabolism / Q000652:urine; D010146:Pain / Q000188:drug therapy; D012015:Reference Standards; D015203:Reproducibility of Results; D015813:Substance Abuse Detection / Q000592:standards*; D053719:Tandem Mass Spectrometry / Q000592:standards
chemical_list: D000700:Analgesics; D013287:Illicit Drugs; D003932:Heroin; D009020:Morphine; D000661:Amphetamine