The Impact and Detection of Driving Impairments Associated With Acute Cannabis Smoking
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| ClinicalTrials.gov Identifier: NCT02849587 |
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Recruitment Status :
Completed
First Posted : July 29, 2016
Results First Posted : January 4, 2022
Last Update Posted : January 4, 2022
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| Condition or disease | Intervention/treatment | Phase |
|---|---|---|
| Cannabis Intoxication | Drug: Cannabis | Phase 1 Phase 2 |
There are several studies that suggest higher doses of whole-blood Δ9-tetrahydrocannabinol (Δ9-THC) concentration are associated with increased crash risk and crash culpability. However, attempts to define a cut-off point for blood Δ9-THC levels have proven to be challenging. Unlike alcohol, for which a level can be reasonably measured using a breathalyzer (and confirmed with a blood test), detection of a cut-off point for intoxication related to Δ9-THC concentration has eluded scientific verification. Recent evidence suggests blood Δ9-THC concentrations of 2-5 ng/mL are associated with substantial driving impairment, particularly in occasional smokers. Others have countered that this level leads to false positives, particularly in heavy cannabis users inasmuch as THC may be detectable in their blood specimens for 12-24 hours after inhalation. Given that 12 to 24 hours is beyond the likely period of driving impairment, this would appear to be a justifiable objection to a per se cut-off point for a Δ9-THC concentration indicative of impairment. Maximal driving impairment is found 20 to 40 minutes after smoking, and the risk of driving impairment decreases over the following hours, at least in those who smoke 18 mg Δ9-THC or less, the dose often used experimentally to duplicate a single joint. Other studies, however, report residual motor vehicle accident crash risk when cannabis is used within 4 hours prior to driving.
The roadside examination using the Standardized Field Sobriety Test (SFST) for proof of cannabis-related impairment has not been an ideal alternative to blood levels. Originally devised to evaluate impairment under the influence of alcohol, the SFST is comprised of three examinations administered in a standardized manner by law enforcement officers. The 'Horizontal Gaze Nystagmus' (HGN), the 'One Leg Stand' (OLS) and the 'Walk and Turn' test (WAT) require a person to follow instructions and perform motor activities. During the assessments, officers observe and record signs of impairment. In one study, Δ9-THC produced impairments on overall SFST performance in 50 % of the participants. In a separate study involving acute administration of cannabis, 30% of people failed the SFST. This discrepancy was thought to be in part due to the participant's cannabis use history, as well as low percentage of THC in the cannabis. The reported frequency of cannabis use varied from once a week to once every 2-6 months in the study where there was a failure on the SFST by 50% of the participants. The other study included more frequent users who smoked cannabis on at least four occasions per week.
Based upon the above, another means is needed to help law enforcement officers discern driving under the influence of cannabis. One future possibility is the development of performance-based measures of cannabis-related impairments. This will include testing of critical tracking, time estimation, balance and visual spatial learning. The investigators have selected brief measures in order to be practicably administered repeatedly over a short time period, as well as tests that have the potential to translate to a field-feasible tablet-based format, should there be benefit in possibly including these in future performance-based measures for use in the field by law enforcement officers (e.g., a cannabis-focused field sobriety test).
| Study Type : | Interventional (Clinical Trial) |
| Actual Enrollment : | 199 participants |
| Allocation: | Randomized |
| Intervention Model: | Parallel Assignment |
| Intervention Model Description: | Participants will be randomized to smoke a cannabis cigarette containing placebo (.02%), 5.9% or 13.4% THC. |
| Masking: | Triple (Participant, Investigator, Outcomes Assessor) |
| Masking Description: | Product will be dispensed from the Research Pharmacy. All assessors, investigators, and participants are blinded to the THC content. |
| Primary Purpose: | Screening |
| Official Title: | A Randomized, Controlled Trial of Cannabis in Healthy Volunteers Evaluating Simulated Driving, Field Performance Tests and Cannabinoid Levels |
| Actual Study Start Date : | February 24, 2017 |
| Actual Primary Completion Date : | June 17, 2019 |
| Actual Study Completion Date : | June 17, 2019 |
| Arm | Intervention/treatment |
|---|---|
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Placebo Comparator: Placebo Cannabis
Subjects will smoke cannabis with placebo THC (.02%) ad libitum
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Drug: Cannabis
Participants will smoke a cannabis cigarette ad libitum as per their usual routine
Other Name: Marijuana |
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Experimental: Cannabis with 5.9% THC
Subjects will smoke cannabis cigarettes with 5.9% THC ad libitum
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Drug: Cannabis
Participants will smoke a cannabis cigarette ad libitum as per their usual routine
Other Name: Marijuana |
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Experimental: Cannabis with 13.4% THC
Subjects will smoke cannabis cigarettes with 13.4% THC ad libitum
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Drug: Cannabis
Participants will smoke a cannabis cigarette ad libitum as per their usual routine
Other Name: Marijuana |
- Change in Composite Drive Score (CDS) From Pre-smoking Simulation [ Time Frame: Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking ]
The Composite Drive Score (CDS) is a z-score comprised of key variables from the simulator tasks (SDLP, speed deviation, and task accuracy during the modified Surrogate Reference Task (mSuRT); coherence from the car following task). This outcome reflects the change in CDS from the pre-smoking assessment, at each timepoint.
The z-score indicates the number of standard deviations away from the mean from the baseline performance for the entire group (n = 191). A Z-score of 0 is equal to the mean of a reference population (in this case the pre-smoking performance for the entire group).
Higher z-scores at each timepoint indicate worse performance (variables that went in the opposite direction were reflected in order to have all variables have the same direction). When examining the change in Composite Drive Score (this outcome variable), a higher score indicates a decline in performance (e.g., Time 2 minus Time 1).
- Simulator: Standard Deviation of Lateral Position (SDLP) [ Time Frame: Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking ]This measures the standard deviation of lateral (lane) position, or the degree to which the participant "swerves" within the road lane on the driving simulation during the modified Surrogate Reference Task (mSuRT). The range is from .39 to 3.33. A higher score indicates worse performance.
- Simulator: Speed Deviation [ Time Frame: Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking ]The variability in speed during the modified Surrogate Reference Test (mSuRT). The speed is in miles per hour. Range is from .17 to 12.85. A higher score indicates worse performance.
- Simulator: Correct Hits on mSuRT [ Time Frame: Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking ]The number of times the participant touched the correct stimulus (circle) on the iPad, during modified Surrogate Reference Task (mSuRT). Range is from 8 to 32. A higher score is a better score.
- Simulator: Car Following - Coherence [ Time Frame: Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking ]Coherence is the correlation (0 to 1) between the participant and the lead car (which speeds up and slows down), representing the participant's ability to accurately speed up and slow down similarly to the lead car. Range of scores is from .01 to .97. A higher score is a better score.
- Simulator: Response Delay - Car Following [ Time Frame: Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking ]Time delay (in seconds) in responding to changes in the lead car's speed. Range is from -5.8 to 6.0. A higher score indicates a worse score.
- Simulator: Distance From Lead Car - Car Following [ Time Frame: Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking ]The outcome is distance from the lead car (in virtual feet) during the Car Following Task
- Tablet Assessment: Dual Attention Missed Switches [ Time Frame: Participants assessed pre-smoking and 1 hour, 2 hours, 4 hours, and 5 hours after smoking ]The participant follows a moving target (square) with her/his finger, and switches to following a new stimulus when it appears in the corner of the screen. Each participant was classified as to whether he/she missed any of these switches during the trial. The outcome is the proportion of participants within each group who missed at least one switch. The range is from 0 to 1. Higher indicates a worse score.
- Tablet Assessment: Lane Tracking Standard Deviation [ Time Frame: Participants assessed pre-smoking and 1 hour, 2 hours, 4 hours, and 5 hours after smoking ]The participant is to rotate the iPad in order to keep a round object in the center, between two lines (lanes). This measure is the standard deviation of the position of the round object during the task (in essence, how much "swerving" there is within the lane). The range is from 8.2 to 189.4. A higher score indicates worse performance.
- Tablet Assessment: Visual Spatial Learning Test Number Correct [ Time Frame: Participants assessed pre-smoking and 1 hour, 2 hours, 4 hours, and 5 hours after smoking ]Assessment of short-term memory for abstract figures. The participant is to memorize abstract figures and their locations on a 3 x 3 grid. After initial viewing (10 seconds), the figures go away for either 4, 12, or 24 seconds. The participant is then to identify which figures were in the initial viewing (from a list at the bottom of the screen), and place them at the correct location. This is the number of correctly identified figures. The range is from 0 to 12. A higher score indicates better performance.
- Tablet Assessment: Time Estimation [ Time Frame: Participants assessed pre-smoking and 1 hour, 2 hours, 4 hours, and 5 hours after smoking ]The participant is to estimate the amount of time that has passed while performing a secondary task. This outcome is the ratio of 1) the estimated time that has passed (seconds), divided by 2) the actual amount of time that has passed. The range is from 0.204 to 1.89. A higher score indicates a better performance.
- Tablet Assessment: Balance [ Time Frame: Participants assessed pre-smoking and 1 hour, 2 hours, 4 hours, and 5 hours after smoking ]While standing and keeping their feet still, this is a measure of the participant's "sway", which is the total distance that the participant's body moved (in meters) from his/her initial vertical position. This was measured using an accelerometer placed on the participant's back. The range of scores is from .222 to 1.661. A higher score indicates worse performance.
- THC Concentrations: Correlation Between Blood and Oral Fluid [ Time Frame: Approximately 15 minutes post-smoking ]Spearman's correlation between THC concentrations in whole blood and oral fluid. Higher scores are better.
- THC Concentrations: Correlation Between Whole Blood and Breath [ Time Frame: Approximately 15 minutes post-smoking ]Spearman's correlation between THC concentrations in whole blood and breath
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| Ages Eligible for Study: | 21 Years to 55 Years (Adult) |
| Sexes Eligible for Study: | All |
| Accepts Healthy Volunteers: | Yes |
Inclusion Criteria:
- Be a licensed driver.
- Need to have acuity of 20/40 or better, with or without correction on a Snellen Visual Acuity eye chart.
Exclusion Criteria:
- At the discretion of the examining physician, individuals with significant cardiovascular, hepatic or renal disease, uncontrolled hypertension, and chronic pulmonary disease (eg, asthma, COPD) will be excluded.
- Unwillingness to abstain from cannabis for 2 days prior to screening and experimental visits
- Positive pregnancy test
- A positive result on toxicity screening for cocaine, amphetamines, opiates, and phencyclidine (PCP) will exclude individuals from participation.
- Unwilling to refrain from driving or operating heavy machinery for four hours after consuming study medication.
To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.
Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT02849587
| United States, California | |
| Center for Medicinal Cannabis Research, UC San Diego | |
| San Diego, California, United States, 92103 | |
| Principal Investigator: | Thomas D Marcotte, PhD | University of California, San Diego |
Documents provided by Thomas D. Marcotte, PhD, University of California, San Diego:
Publications of Results:
Other Publications:
Publications automatically indexed to this study by ClinicalTrials.gov Identifier (NCT Number):
| Responsible Party: | Thomas D. Marcotte, PhD, Professor, University of California, San Diego |
| ClinicalTrials.gov Identifier: | NCT02849587 |
| Other Study ID Numbers: |
160641 |
| First Posted: | July 29, 2016 Key Record Dates |
| Results First Posted: | January 4, 2022 |
| Last Update Posted: | January 4, 2022 |
| Last Verified: | December 2021 |
| Individual Participant Data (IPD) Sharing Statement: | |
| Plan to Share IPD: | Yes |
| Plan Description: | Data to facilitate meta-analyses |
| Supporting Materials: |
Study Protocol Statistical Analysis Plan (SAP) Informed Consent Form (ICF) |
| Time Frame: | Upon manuscript publications |
| Access Criteria: | Approved researchers |
| Studies a U.S. FDA-regulated Drug Product: | Yes |
| Studies a U.S. FDA-regulated Device Product: | No |
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Driving Under the Influence Memory Impairment Reaction Time Time Perception Cannabis |
Marijuana Whole Blood Oral Fluid Breath Driving simulator |
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Marijuana Abuse Substance-Related Disorders Chemically-Induced Disorders Mental Disorders |