title: THCCOOH concentrations in whole blood: are they useful in discriminating occasional from heavy smokers?
abstract: Some forensic and clinical circumstances require knowledge of the frequency of drug use. Care of the patient, administrative, and legal consequences will be different if the subject is a regular or an occasional cannabis smoker. To this end, 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH) has been proposed as a criterion to help to distinguish between these two groups of users. However, to date this indicator has not been adequately assessed under experimental conditions. We carried out a controlled administration study of smoked cannabis with a placebo. Cannabinoid levels were determined in whole blood using tandem mass spectrometry. Significantly high differences in THCCOOH concentrations were found between the two groups when measured during the screening visit, prior to the smoking session, and throughout the day of the experiment. Receiver operating characteristic (ROC) curves were determined and two threshold criteria were proposed in order to distinguish between these groups: a free THCCOOH concentration below 3 µg/L suggested an occasional consumption (≤ 1 joint/week) while a concentration higher than 40 µg/L corresponded to a heavy use (≥ 10 joints/month). These thresholds were tested and found to be consistent with previously published experimental data. The decision threshold of 40 µg/L could be a cut-off for possible disqualification for driving while under the influence of cannabis. A further medical assessment and follow-up would be necessary for the reissuing of a driving license once abstinence from cannabis has been demonstrated. A THCCOOH level below 3 µg/L would indicate that no medical assessment is required.
authors.affiliation: CURML (University Center of Legal Medicine), UTCF (Forensic Toxicology and Chemistry Unit), Lausanne and Geneva, Switzerland.
authors.forename: Marie
authors.initials: M
authors.lastname: Fabritius
authors.forename: Bernard
authors.initials: B
authors.lastname: Favrat
authors.forename: Haithem
authors.initials: H
authors.lastname: Chtioui
authors.forename: Giovanni
authors.initials: G
authors.lastname: Battistella
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Annoni
authors.forename: Monique
authors.initials: M
authors.lastname: Appenzeller
authors.forename: Kim
authors.initials: K
authors.lastname: Dao
authors.forename: Eleonora
authors.initials: E
authors.lastname: Fornari
authors.forename: Estelle
authors.initials: E
authors.lastname: Lauer
authors.forename: Jean-Frédéric
authors.initials: JF
authors.lastname: Mall
authors.forename: Philippe
authors.initials: P
authors.lastname: Maeder
authors.forename: Patrice
authors.initials: P
authors.lastname: Mangin
authors.forename: Christian
authors.initials: C
authors.lastname: Staub
authors.forename: Christian
authors.initials: C
authors.lastname: Giroud
mesh_terms: D000293:Adolescent; D000328:Adult; D063386:Cannabinoid Receptor Agonists / Q000097:blood*; D013759:Dronabinol / Q000031:analogs & derivatives* / Q000097:blood; D006801:Humans; D008385:Marijuana Smoking / Q000097:blood*; D015813:Substance Abuse Detection; D053719:Tandem Mass Spectrometry; D055815:Young Adult
chemical_list: D063386:Cannabinoid Receptor Agonists; C016780:11-nor-delta(9)-tetrahydrocannabinol-9-carboxylic acid; D013759:Dronabinol
keywords: THCCOOH; cannabis; heavy use; occasional use; whole blood