• Drug Policy Implications of Inhaled Cannabis: Driving Skills and Subjective Effects, Vaporized Cannabinoid Pharmacokinetics, and Interactions with Alcohol

      Hartman, Rebecca Lynn; Huestis, Marilyn; 0000-0002-1960-3296 (2015)
      Increasing medical and recreational cannabis legalization and shifting public attitudes are accompanied by increased driving under the influence of cannabis (DUIC) cases and changing administration routes, including vaporization. Cannabis' driving effects are poorly understood, and cannabis driving per se laws heavily debated--especially when considering blood collection delays. Cannabis and alcohol are frequently encountered together in drugged driving cases, but interactive effects are not fully elucidated. Oral fluid (OF) is an advantageous alternative matrix for documenting cannabis exposure, with interest in correlating cannabis' effects with OF cannabinoid concentrations. This research aimed to 1) evaluate cannabis' effect on driving lateral control relative to blood delta9-tetrahydrocannabinol (THC) concentrations, with and without alcohol; 2) assess vaporized cannabis' subjective effects and pharmacokinetic disposition in blood, plasma, and OF, with and without alcohol. Current cannabis smokers drank placebo or low-dose alcohol and inhaled vaporized placebo, low (2.9%), or high (6.7%)-THC vaporized bulk cannabis (6 conditions, within-subject). Participants drove 45min simulated drives 0.5h post-dose. Subjective effects, blood and OF, and breath alcohol concentration (BrAC) were measured at baseline and up to 8.3h post-dose. Cannabis increased standard deviation of lateral position (SDLP, lane weaving) but not maximum lateral acceleration or lane departures/min. BrAC increased all three; cannabis-alcohol SDLP effects were additive rather than synergistic. Cannabinoids' time courses and subjective effects exhibited patterns similar to those after smoking, with THC maximum concentration (Cmax) occurring immediately post-dose and decreasing rapidly thereafter, then subsequent slower excretion. Approximately half of participants self-titrated doses to individual comfort levels via inhalation technique, resulting in similar THC Cmax after low and high doses. Blood THC concentrations 7-10ug/L during driving increased SDLP similarly to 0.05g/210L [impairing] BrAC; 20ug/L, more than 0.08g/210L [US illegal BrAC]. Because SDLP effects were additive, 5ug/L THC+0.05g/210L alcohol produced similar SDLP to 0.08g/210L. Blood THC during driving generally is much higher than at time of blood draw in authentic DUIC cases. OF cannabinoids documented intake, but THC concentration variability limited interpretation. Data demonstrate significant cannabis effects on driving, provide blood and OF concentrations after vaporized cannabis, and will benefit clinicians and policymakers by improving DUIC and clinical interpretation.
    • Effectiveness of an ignition interlock device in reducing alcohol-impaired driving recidivism and alcohol-impaired motor vehicle crashes in Maryland

      Kerns, Timothy; Smith, Gordon S., M.B., Ch.B., M.P.H.; Hirshon, Jon Mark (2017)
      Background: Multiple studies have shown that ignition interlock devices reduce alcohol impaired driving recidivism while the device is installed on the vehicle. However, many of these studies rely on convictions and have limited follow-up after the device has been removed from the vehicle. Objectives: The aims of this study were to compare the characteristics of drivers who installed an ignition interlock device after receiving an alcohol impaired driving citation and a control group that did not install the device and to determine their risk of receiving a subsequent alcohol related citation or being involved in an alcohol related crash. Methods: A Cox proportional hazard test was used to compare the risk of a subsequent citation or motor vehicle crash between the study groups. Results: The interlock group had a lower proportion of females (22.2% interlock vs 24.2% control, p<0.05), and a higher mean age (36.5 years vs 34.3 years, p<0.05). Forty-six percent of those installing an ignition interlock device had a BAC above 0.15 g/dL as compared with 25% in the control group (p<0.05). The BAC test refusal rate was higher among interlock installers (41.4% vs 33.0%, p<0.05). While the device was installed on the subject's vehicle, drivers were 22% less likely to receive an impaired driving citation as compared to the time when the device was not installed (HR=0.78; 95% CI: 0.73-0.84). After removal, the interlock group was 32% more likely to receive an impaired driving citation versus controls (HR=1.32; 95% CI: 1.22-1.42). Similar patterns were observed with respect to motor vehicle crashes. Conclusion: Drivers who have installed an ignition device on their vehicle have a lower risk of receiving a subsequent alcohol involved driving citation and of being involved in an alcohol related motor vehicle crash while the device is on the vehicle as compared to the control group. Upon removal, the risk of both citations and crashes is higher for those who had an interlock device installed. Ignition interlock devices are effective for the time they are used but should not be the only tool to prevent future events of alcohol involved driving among those previously arrested for impaired driving.