Rebecca L Hartman1, Timothy L Brown2, Gary Milavetz3, Andrew Spurgin3, David A Gorelick4, Gary R Gaffney5, Marilyn A Huestis6. 1. Chemistry and Drug Metabolism, Intramural Research Program, National Institute on Drug Abuse, NIH, Baltimore, MD; 2. National Advanced Driving Simulator, University of Iowa, Iowa City, IA; 3. College of Pharmacy, University of Iowa, Iowa City, IA; 4. Chemistry and Drug Metabolism, Intramural Research Program, National Institute on Drug Abuse, NIH, Baltimore, MD; Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD; 5. Carver College of Medicine, University of Iowa, Iowa City, IA. 6. Chemistry and Drug Metabolism, Intramural Research Program, National Institute on Drug Abuse, NIH, Baltimore, MD; mhuestis@intra.nida.nih.gov.
Abstract
BACKGROUND: In driving-under-the-influence cases, blood typically is collected approximately 1.5-4 h after an incident, with unknown last intake time. This complicates blood Δ(9)-tetrahydrocannabinol (THC) interpretation, owing to rapidly decreasing concentrations immediately after inhalation. We evaluated how decreases in blood THC concentration before collection may affect interpretation of toxicological results. METHODS:Adult cannabis smokers (≥1×/3 months, ≤3 days/week) drank placebo or low-dose alcohol (approximately 0.065% peak breath alcohol concentration) 10 min before inhaling 500 mg placebo, 2.9%, or 6.7% vaporized THC (within-individuals), then took simulated drives 0.5-1.3 h postdose. Blood THC concentrations were determined before and up to 8.3 h postdose (limit of quantification 1 μg/L). RESULTS: In 18 participants, observed Cmax (at 0.17 h) for active (2.9 or 6.7% THC) cannabis were [median (range)] 38.2 μg/L (11.4-137) without alcohol and 47.9 μg/L (13.0-210) with alcohol. THC Cmax concentration decreased 73.5% (3.3%-89.5%) without alcohol and 75.1% (11.5%-85.4%) with alcohol in the first half-hour after active cannabis and 90.3% (76.1%-100%) and 91.3% (53.8%-97.0%), respectively, by 1.4 h postdose. When residual THC (from previous self-administration) was present, concentrations rapidly decreased to preinhalation baselines and fluctuated around them. During-drive THC concentrations previously associated with impairment (≥8.2 μg/L) decreased to median <5 μg/L by 3.3 h postdose and <2 μg/L by 4.8 h postdose; only 1 participant had THC ≥5 μg/L after 3.3 h. CONCLUSIONS:Forensic blood THC concentrations may be lower than common per se cutoffs despite greatly exceeding them while driving. Concentrations during driving cannot be back-extrapolated because of unknown time after intake and interindividual variability in rates of decrease.
RCT Entities:
BACKGROUND: In driving-under-the-influence cases, blood typically is collected approximately 1.5-4 h after an incident, with unknown last intake time. This complicates blood Δ(9)-tetrahydrocannabinol (THC) interpretation, owing to rapidly decreasing concentrations immediately after inhalation. We evaluated how decreases in blood THC concentration before collection may affect interpretation of toxicological results. METHODS: Adult cannabis smokers (≥1×/3 months, ≤3 days/week) drank placebo or low-dose alcohol (approximately 0.065% peak breath alcohol concentration) 10 min before inhaling 500 mg placebo, 2.9%, or 6.7% vaporized THC (within-individuals), then took simulated drives 0.5-1.3 h postdose. Blood THC concentrations were determined before and up to 8.3 h postdose (limit of quantification 1 μg/L). RESULTS: In 18 participants, observed Cmax (at 0.17 h) for active (2.9 or 6.7% THC) cannabis were [median (range)] 38.2 μg/L (11.4-137) without alcohol and 47.9 μg/L (13.0-210) with alcohol. THC Cmax concentration decreased 73.5% (3.3%-89.5%) without alcohol and 75.1% (11.5%-85.4%) with alcohol in the first half-hour after active cannabis and 90.3% (76.1%-100%) and 91.3% (53.8%-97.0%), respectively, by 1.4 h postdose. When residual THC (from previous self-administration) was present, concentrations rapidly decreased to preinhalation baselines and fluctuated around them. During-drive THC concentrations previously associated with impairment (≥8.2 μg/L) decreased to median <5 μg/L by 3.3 h postdose and <2 μg/L by 4.8 h postdose; only 1 participant had THC ≥5 μg/L after 3.3 h. CONCLUSIONS: Forensic blood THC concentrations may be lower than common per se cutoffs despite greatly exceeding them while driving. Concentrations during driving cannot be back-extrapolated because of unknown time after intake and interindividual variability in rates of decrease.
Authors: Benedikt Fischer; Cayley Russell; Pamela Sabioni; Wim van den Brink; Bernard Le Foll; Wayne Hall; Jürgen Rehm; Robin Room Journal: Am J Public Health Date: 2017-06-23 Impact factor: 9.308
Authors: Jeffrey R Brubacher; Herbert Chan; Shannon Erdelyi; Scott Macdonald; Mark Asbridge; Robert E Mann; Jeffrey Eppler; Adam Lund; Andrew MacPherson; Walter Martz; William E Schreiber; Rollin Brant; Roy A Purssell Journal: Addiction Date: 2019-07-03 Impact factor: 6.526