title: Impact of prolonged cannabinoid excretion in chronic daily cannabis smokers' blood on per se drugged driving laws.
abstract: BACKGROUND
  Cannabis is the illicit drug most frequently reported with impaired driving and motor vehicle accidents. Some "per se" laws make it illegal to drive with any amount of drug in the body, while others establish blood, saliva, or urine concentrations above which it is illegal to drive. The persistence of Δ(9)-tetrahydrocannabinol (THC) in chronic daily cannabis smokers' blood is unknown.
  
  
  METHODS
  Thirty male chronic daily cannabis smokers resided on a secure research unit for up to 33 days, with daily blood collection. Samples were processed in an ice bath during sample preparation to minimize cannabinoid adsorption onto precipitant material. We quantified THC by 2-dimensional GC-MS.
  
  
  RESULTS
  Of the 30 participants, 27 were THC-positive on admission, with a median (range) concentration of 1.4 μg/L (0.3-6.3). THC decreased gradually; only 1 of 11 participants was negative at 26 days, 2 of 5 remained THC-positive (0.3 μg/L) for 30 days, and 5.0% of participants had THC ≥ 1.0 μg/L for 12 days. Median 11-hydroxy-THC concentrations were 1.1 μg/L on admission, with no results ≥ 1.0 μg/L 24 h later. 11-Nor-9-carboxy-THC (THCCOOH) detection rates were 96.7% on admission, decreasing slowly to 95.7% and 85.7% on days 8 and 22, respectively; 4 of 5 participants remained THCCOOH positive (0.6-2.7 μg/L) after 30 days, and 1 remained positive on discharge at 33 days.
  
  
  CONCLUSIONS
  Cannabinoids can be detected in blood of chronic daily cannabis smokers during a month of sustained abstinence. This is consistent with the time course of persisting neurocognitive impairment reported in recent studies.
authors: Chemistry and Drug Metabolism, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA.
authors: Mateus M
authors: MM
authors: Bergamaschi
authors: Erin L
authors: EL
authors: Karschner
authors: Robert S
authors: RS
authors: Goodwin
authors: Karl B
authors: KB
authors: Scheidweiler
authors: Jussi
authors: J
authors: Hirvonen
authors: Regina H C
authors: RH
authors: Queiroz
authors: Marilyn A
authors: MA
authors: Huestis
mesh_terms: D000328:Adult; D001334:Automobile Driving / Q000331:legislation & jurisprudence*; D013759:Dronabinol / Q000031:analogs & derivatives / Q000097:blood*; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000097:blood*; D008875:Middle Aged; D015813:Substance Abuse Detection
chemical_list: C016780:11-nor-delta(9)-tetrahydrocannabinol-9-carboxylic acid; D013759:Dronabinol