Indeterminacy of cannabis impairment and ∆9-tetrahydrocannabinol (∆9-THC) levels in blood and breath

Abstract

Previous investigators have found no clear relationship between specific blood concentrations of ∆9-tetrahydrocannabinol (∆9-THC) and impairment, and thus no scientific justification for use of legal “per se” ∆9-THC blood concentration limits. Analyzing blood from 30 subjects showed ∆9-THC concentrations that exceeded 5 ng/mL in 16 of the 30 subjects following a 12-h period of abstinence in the absence of any impairment. In blood and exhaled breath samples collected from a group of 34 subjects at baseline prior to smoking, increasing breath ∆9-THC levels were correlated with increasing blood levels (P < 0.0001) in the absence of impairment, suggesting that single measurements of ∆9-THC in breath, as in blood, are not related to impairment. When post-smoking duration of impairment was compared to baseline ∆9-THC blood concentrations, subjects with the highest baseline ∆9-THC levels tended to have the shortest duration of impairment. It was further shown that subjects with the shortest duration of impairment also had the lowest incidence of horizontal gaze nystagmus at 3 h post-smoking compared to subjects with the longest duration of impairment (P < 0.05). Finally, analysis of breath samples from a group of 44 subjects revealed the presence of transient cannabinoids such as cannabigerol, cannabichromene, and ∆9-tetrahydrocannabivarin during the peak impairment window, suggesting that these compounds may be key indicators of recent cannabis use through inhalation. In conclusion, these results provide further evidence that single measurements of ∆9-THC in blood, and now in exhaled breath, do not correlate with impairment following inhalation, and that other cannabinoids may be key indicators of recent cannabis inhalation.

Examining impairment and kinetic patterns associated with recent use of hemp-derived Δ8-tetrahydrocannabinol: case studies

“…The available literature does, however, suggest that ∆ 8 -THC and ∆ 9 -THC are pharmacodynamically quite similar (Hazekamp et al 2010 ; Abrahamov et al 1995 ; Kruger and Kruger 2021 ; Kruger and Kruger 2022 ), which is consistent with the findings of the present study. Prior to smoking ∆ 9 -THC in the previous study, the subjects showed no evidence of impairment despite measurable blood ∆ 9 -THC levels, which is consistent with recently published studies showing no significant correlation between impairment and specific blood concentrations of ∆ 9 -THC (Brubacher et al 2019 ; Hartman et al 2016 ; McCartney et al 2022 ; Hubbard et al 2021 ; Wurz and DeGregorio 2022 ).…”

Does the co-use of cannabis exacerbate the effect of alcohol on the risk of crashing? A systematic review and meta-analysis

“…The degree of impairment resulting from cannabis use is clearly related to the dosage administered (e.g., Schlienz et al, 2020). However, that relationship does not seem to translate into demonstrable dose-response relationship between the concentration of THC in the blood or oral fluid and either the level of impairment (Arkell et al, 2021; White and Burns, 2022b: 16-18; Wurz and DeGregorio, 2022) or the risk of crashing (Macdonald, 2018: 96; White and Burns, 2021: 12-13). Nevertheless, it is certainly possible to get so intoxicated on cannabis that one is incapable of safely driving a car.…”

An analytical approach for on‐site analysis of breath samples for Δ9‐tetrahydrocannabinol (THC)

“…The determination of therapeutic drugs in human breath has been reported 25 as well as toxicology applications where a number of abused drugs have been detected shortly after intake 26 . Part of the success of these easier sample collection techniques is the improvement in sensitivity and selectivity of modern LC/MS techniques 25,27–29 …”

“…26 Part of the success of these easier sample collection techniques is the improvement in sensitivity and selectivity of modern LC/MS techniques. 25,[27][28][29] In the recent past, a first-generation breath collection device was reported, which described the LC/MS/MS determination of a series of common drugs of abuse in subjects who had taken these drugs. 30 A subsequent report described the direct real-time measurement of volatiles in human breath with a compact mass spectrometer using atmospheric pressure chemical ionization (APCI) but without LC/MS coupling.…”