title: Exercise increases plasma THC concentrations in regular cannabis users.
abstract: BACKGROUND
  The major psychoactive ingredient of cannabis, Δ(9)-tetrahydrocannabinol (THC) accumulates in fat tissue from where it slowly diffuses back into blood. THC pre-treated rats can show elevated plasma cannabinoid levels when subjected to conditions that promote fat utilization, such as fasting. Here we examine whether fasting and exercise increase plasma THC concentrations in regular cannabis users.
  
  
  METHODS
  Fourteen regular cannabis users completed 35 min of exercise on a stationary bicycle in either a fed or overnight fasted state. Plasma cannabinoid levels were assessed prior to exercise, immediately post-exercise and 2h post-exercise. Plasma samples were also analyzed for indices of lipolysis (free fatty acids (FFA) and glycerol).
  
  
  RESULTS
  Exercise induced a small, statistically significant increase in plasma THC levels accompanied by increased plasma FFA and glycerol levels. Exercise-induced increases in plasma THC concentrations were positively correlated with body mass index. Fasting induced a significant increase in plasma FFA levels, and a lowering of blood glucose, but did not significantly alter plasma cannabinoid levels.
  
  
  CONCLUSIONS
  Here we demonstrate that exercise enhances plasma THC levels in regular cannabis users. The lack of a fasting effect may reflect the modest duration of fasting used which was associated with only a modest increase in fat utilization relative to exercise. Overall, these results suggest that exercise may elevate blood THC levels by releasing dormant THC from fat stores. These data suggest the interpretation of blood THC levels in roadside and workplace tests might be complicated by recent exercise.
authors.affiliation: The Discipline of Pharmacology, The University of Sydney, NSW 2006, Australia.
authors.forename: Alexander
authors.initials: A
authors.lastname: Wong
authors.forename: Mark E
authors.initials: ME
authors.lastname: Montebello
authors.forename: Melissa M
authors.initials: MM
authors.lastname: Norberg
authors.forename: Kieron
authors.initials: K
authors.lastname: Rooney
authors.forename: Nicholas
authors.initials: N
authors.lastname: Lintzeris
authors.forename: Raimondo
authors.initials: R
authors.lastname: Bruno
authors.forename: Jessica
authors.initials: J
authors.lastname: Booth
authors.forename: Jonathon C
authors.initials: JC
authors.lastname: Arnold
authors.forename: Iain S
authors.initials: IS
authors.lastname: McGregor
mesh_terms: D000293:Adolescent; D001642:Bicycling; D015992:Body Mass Index; D015331:Cohort Studies; D013759:Dronabinol / Q000097:blood*; D015444:Exercise / Q000502:physiology*; D005215:Fasting / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D005990:Glycerol / Q000097:blood; D006801:Humans; D008297:Male; D008385:Marijuana Smoking / Q000097:blood*; D055815:Young Adult
chemical_list: D005230:Fatty Acids, Nonesterified; D013759:Dronabinol; D005990:Glycerol
keywords: Cannabis; Exercise; Fasting; Lipolysis; Reintoxication; Δ(9)-Tetrahydrocannabinol