title: Rapid elimination of Carboxy-THC in a cohort of chronic cannabis users.
abstract: Urinary 11-nor-Δ(9)-tetrahydrocannabinol-9-carboxylic acid (Carboxy-THC) concentrations, normalised to creatinine output, have been demonstrated to be a useful tool in the interpretation of the results of a series of urine tests for cannabis. These tests, often termed historical data, can be used to identify potential chronic cannabis users who may present occupational health and safety risks within the workplace. Conversely, the data can also be used to support employee claims of previous regular, rather than recent, cannabis use. This study aimed at examining the mean elimination of Carboxy-THC in 37 chronic users undergoing voluntary abstinence over a 2-week period. Urine specimens were collected prior to the study and after 1 and 2 weeks of abstinence. Carboxy-THC levels in urine were measured by gas chromatography-mass spectrometry (GC-MS) following alkaline hydrolysis, organic solvent extraction and derivatisation to form its pentafluoropropionic derivative. The creatinine-normalised Carboxy-THC concentrations declined rapidly over the 2 weeks of abstinence period and the majority of chronic cannabis users (73%) reduced their urinary Carboxy-THC levels to below the 15-μg/L confirmatory cutoff within that time. The study further highlights the value of historical urinary Carboxy-THC data as a means of identifying potential occupational health and safety risks among chronic cannabis users.
authors.affiliation: Centre for Forensic Science, University of Technology Sydney (UTS), Broadway, Sydney, NSW, 2007, Australia.|National Cannabis Prevention and Information Centre, UNSW Medicine, Sydney, NSW, 2052, Australia.
authors.forename: John
authors.initials: J
authors.lastname: Lewis
authors.affiliation: Centre for Forensic Science, University of Technology Sydney (UTS), Broadway, Sydney, NSW, 2007, Australia.
authors.forename: Anna
authors.initials: A
authors.lastname: Molnar
authors.affiliation: National Cannabis Prevention and Information Centre, UNSW Medicine, Sydney, NSW, 2052, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Allsop
authors.affiliation: National Cannabis Prevention and Information Centre, UNSW Medicine, Sydney, NSW, 2052, Australia.
authors.forename: Jan
authors.initials: J
authors.lastname: Copeland
authors.affiliation: Centre for Forensic Science, University of Technology Sydney (UTS), Broadway, Sydney, NSW, 2007, Australia. shanlin.fu@uts.edu.au.
authors.forename: Shanlin
authors.initials: S
authors.lastname: Fu
mesh_terms: D015331:Cohort Studies; D013759:Dronabinol / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000652:urine; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D002189:Marijuana Abuse / Q000652:urine*; D011619:Psychotropic Drugs / Q000493:pharmacokinetics / Q000652:urine*; D015813:Substance Abuse Detection
chemical_list: D011619:Psychotropic Drugs; C016780:11-nor-delta(9)-tetrahydrocannabinol-9-carboxylic acid; D013759:Dronabinol
keywords: Cannabis; Carboxy-THC; THCCOOH; Urine drug testing