title: Extended urinary Delta9-tetrahydrocannabinol excretion in chronic cannabis users precludes use as a biomarker of new drug exposure.
abstract: BACKGROUND
  Generally, urinary 11-nor-9-carboxy-Delta9-tetrahydrocannabinol (THCCOOH) after alkaline hydrolysis is monitored to detect cannabis exposure, although last use may have been weeks prior in chronic cannabis users. Delta9-Tetrahydrocannabinol (THC) and 11-hydroxy-THC (11-OH-THC) concentrations in urine following Escherichia coli beta-glucuronidase hydrolysis were proposed as biomarkers of recent (within 8h) cannabis use.
  
  
  OBJECTIVE
  To test the validity of THC and 11-OH-THC in urine as indicators of recent cannabis use.
  
  
  METHODS
  Monitor urinary cannabinoid excretion in 33 chronic cannabis smokers who resided on a secure research unit under 24h continuous medical surveillance. All urine specimens were collected individually ad libidum for up to 30 days, were hydrolyzed with a tandem E. coli beta-glucuronidase/base procedure, and analyzed for THC, 11-OH-THC and THCCOOH by one- and two-dimensional-cryotrap gas chromatography mass spectrometry (2D-GCMS) with limits of quantification of 2.5 ng/mL.
  
  
  RESULTS
  Extended excretion of THC and 11-OH-THC in chronic cannabis users' urine was observed during monitored abstinence; 14 of 33 participants had measurable THC in specimens collected at least 24h after abstinence initiation. Seven subjects had measurable THC in urine for 3, 3, 4, 7, 7, 12, and 24 days after cannabis cessation. 11-OH-THC and THCCOOH were detectable in urine specimens from one heavy, chronic cannabis user for at least 24 days.
  
  
  CONCLUSIONS
  For the first time, extended urinary excretion of THC and 11-OH-THC is documented for at least 24 days, negating their effectiveness as biomarkers of recent cannabis exposure, and substantiating long terminal elimination times for urinary cannabinoids following chronic cannabis smoking.
authors.affiliation: Chemistry and Drug Metabolism, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Biomedical Research Center, 251 Bayview Boulevard, Suite 05A721, Baltimore, MD 21224, USA.
authors.forename: Ross H
authors.initials: RH
authors.lastname: Lowe
authors.forename: Tsadik T
authors.initials: TT
authors.lastname: Abraham
authors.forename: William D
authors.initials: WD
authors.lastname: Darwin
authors.forename: Ronald
authors.initials: R
authors.lastname: Herning
authors.forename: Jean Lud
authors.initials: JL
authors.lastname: Cadet
authors.forename: Marilyn A
authors.initials: MA
authors.lastname: Huestis
mesh_terms: D000328:Adult; D015415:Biomarkers; D002908:Chronic Disease; D013759:Dronabinol / Q000031:analogs & derivatives / Q000652:urine*; D005006:Ethnicity; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000652:urine*; D015813:Substance Abuse Detection / Q000379:methods*; D019966:Substance-Related Disorders / Q000150:complications / Q000652:urine; D055815:Young Adult
chemical_list: D015415:Biomarkers; C001427:11-hydroxy-delta(9)-tetrahydrocannabinol; D013759:Dronabinol; C025351:delta(9)-tetrahydrocannabinolic acid