1. Impact of Prolonged Cannabinoid Excretion in Chronic Daily Cannabis Smokers' Blood on Per Se Drugged Driving Laws M.M. Bergamaschi, E.L. Karschner, R.S. Goodwin, K.B. Scheidweiler, J. Hirvonen, R.H.C. Queiroz, and M.A. Huestis March 2013 www.clinchem.org/content/59/3/519.full © Copyright 2013 by the American Association for Clinical Chemistry

2. © Copyright 2009 by the American Association for Clinical Chemistry Introduction  Cannabis (marijuana)  Most commonly used illicit drug worldwide  Estimated 17.4 million Americans age 12 years or older smoked cannabis in 2010, with 6600 new initiates daily  Primary psychoactive component, ∆ 9 -tetrahydrocannabinol (THC) metabolized  11-hydroxy-THC (11-OH-THC) and 11-nor-9-carboxy-THC (THCCOOH)  Cannabis & driving  Cannabis 2nd only to alcohol for causing impaired driving and motor vehicle accidents  In 2007 National Roadside Survey, more drivers tested positive for drugs (16.6%) than for alcohol (12.4%)

3. © Copyright 2009 by the American Association for Clinical Chemistry Introduction  Cannabis & driving  Cannabis smokers had 10-fold increase in car crash injury compared with infrequent or nonusers  THC blood concentrations ≥5 μg/L associated with 6.6-fold increase in driver responsibility for driving fatalities  Legal blood THC concentration limits  15 US states and 12 European countries have established THC concentration limits in blood  4 European countries established limits in plasma or serum

4. © Copyright 2009 by the American Association for Clinical Chemistry Introduction  THC blood concentrations may be low or not detected while brain concentrations might be sufficient to cause impairment  Difficult to identify minimum blood THC concentration consistently associated with impairment  No study has characterized cannabinoid elimination in blood from daily cannabis smokers during monitored sustained abstinence for up to 33 days

5. © Copyright 2009 by the American Association for Clinical Chemistry Questions  How does prolonged cannabinoid excretion complicate interpretation of cannabinoid blood concentrations in clinical and forensic cases?  Are there other cannabinoids in blood and/or other cutoffs to indicate recent cannabis smoking?

6. © Copyright 2009 by the American Association for Clinical Chemistry Materials & Methods  Participants  30 male chronic daily cannabis smokers resided on a secure research unit for up to 33 days under 24-hour surveillance  Sample collection  Blood collected once daily and stored at -20˚C  Blood cannabinoid analysis  THC,11-OH-THC and THCCOOH simultaneously quantified by 2-dimensional gas chromatography-mass spectrometry

7. © Copyright 2009 by the American Association for Clinical Chemistry Materials & Methods  Limits of quantification (LOQ)  THC and THCCOOH: 0.25 µg/L  11-OH-THC: 0.5 µg/L  Data analysis  Correlation: Spearman rank correlation  Comparative analysis: Wilcoxon rank test  Survival analysis: Kaplan-Meier analysis

8. © Copyright 2009 by the American Association for Clinical Chemistry Question  Why were cannabinoid blood detection rates calculated at different cutoffs?

9. © Copyright 2009 by the American Association for Clinical Chemistry Results  30 male chronic daily cannabis smokers provided a total of 570 blood samples over 1 – 4 weeks  Mean (SD) age 28.3 (7.9) years  Mean (SD) 10.2 (6.3) joints/day for 11.7 (7.5) years  326 THC positive (57.2%) 0.25 – 6.3 μg/L  33 11-OH-THC positive (5.8%) ≤4.1 μg/L  531 THCCOOH (93.2%) 0.25 – 93.4 μg/L

10. © Copyright 2009 by the American Association for Clinical Chemistry Results  Cannabinoid excretion during sustained abstinence in 30 chronic cannabis smokers  Admission: 27 of 30 participants THC positive, 77.8% ≥ 1.0 μg/L and 11.1% ≥ 5.0 μg/L  Only 1 of 11 was negative at 26 days, 2 of 5 remained THC-positive (0.3 μg/L) for 30 days  Median 11-OH-THC 1.1 µg/L on admission, all ≤1.0 by 24 hours  THCCOOH detection rates 96.7% on admission, 95.7% day 8, 85.7% day 22  4 of 5 THCCOOH positive for 30 days (0.6 – 2.7 μg/L). All subjects’ blood THC ≤ 1 μg/L within 7 days

11. © Copyright 2009 by the American Association for Clinical Chemistry Results  Cannabinoid excretion during sustained abstinence in 30 chronic cannabis smokers  2 participants were THC-positive on day 30 (0.3 μg/L)  1 participant had THCCOOH of 0.7 μg/L on day 33 of abstinence

12. © Copyright 2009 by the American Association for Clinical Chemistry Results

13. Results  Median THC & 11-OH-THC last detection times were 22 days (95% CI 17.8 – 26.2 days) and 1 day (95% CI 0 days)  THC last detection times were significantly correlated with number of cannabis joints smoked per day (r = 0.372; P = 0.047)

14. © Copyright 2009 by the American Association for Clinical Chemistry Question  What are the possible advantages of using different cannabinoids for interpretation of cannabinoid test results?

15. © Copyright 2009 by the American Association for Clinical Chemistry Conclusions  Cannabinoids detected in blood of chronic daily cannabis smokers during 1 month sustained abstinence  Consistent with time course of persisting neurocognitive and psychomotor impairment reported in recent studies  Extended residual THC excretion in chronic daily cannabis smokers complicates interpretation of cannabinoid tests  Strong public safety need to reduce morbidity and mortality from cannabis-impaired driving

16. © Copyright 2009 by the American Association for Clinical Chemistry Thank you for participating in this month’s Clinical Chemistry Journal Club. Additional Journal Clubs are available at www.clinchem.org Download the free Clinical Chemistry app on iTunes for additional content! Follow us