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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Date data sharing statement initially provided
Date results information initially provided
Type of registration
Prospectively registered

Titles & IDs
Public title
The effects of medicinal cannabinoids on driving
Scientific title
The effects of medicinal cannabinoids on driving in healthy adults with prior cannabis experience
Secondary ID [1] 288440 0
Nil known
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Driving ability under the influence of the cannabinoids tetrahydrocannabidiol (THC) and cannbidiol (CBD) 297463 0
Condition category
Condition code
Other 297652 297652 0 0
Research that is not of generic health relevance and not applicable to specific health categories listed above

Study type
Description of intervention(s) / exposure
The study is a randomized, crossover, double blind trial comparing the effects of .125g inhaled vaporized cannabis containing various concentrations of tetrahydrocannabinol (THC) and cannabidiol (CBD) on driving performance. Participants will complete 3 sessions, seperated by a washout period of 7 days. Participants will receive one of three varieties of cannabis per session, in a randomised and counter-balanced order. Cannabis types will include cannabis containing either: (a) high THC/low CBD (11% THC / <1% CBD), (b) high THC/high CBD (11% THC / 11% CBD) or (c) placebo. Study medications will be administered using a Volcano Medic vaporiser under the supervision of study staff.. To assess driving ability, participants will complete a 45-minute advanced driving simulation, beginning 15 minutes after drug administration. Participants will additionally complete a series of cognitive tests designed to measure reaction time. attentional processing and executive function. Biological samples (urine, blood and saliva) will be taken before and at a series of time points following drug administration. These will later be analysed for THC, CBD and endocannabinoids.
Intervention code [1] 293766 0
Other interventions
Comparator / control treatment
The control arm of this study involves a placebo strain of cannabis that contains negligible amounts of THC and CBD. All participants will receive this placebo strain during one of the three sessions,
Control group

Primary outcome [1] 297190 0
The primary outcome measure is Standard deviation of lateral position (SDLP), which is measured by Oktal SCANeR Studio driving simulation software.
Timepoint [1] 297190 0
The primary outcome is measured twice during two driving simulation tasks; the first occurs 30 minutes after drug administration, and the second ocurs 2 1/2 hours after drug administration.
Secondary outcome [1] 320280 0
Subjective measures of drug effects and driving ability, assessed by a VAS ranging from 0-100. These include:

1. Strength of drug effect (No effect – Very strong)
2. Liking of drug effect (Disliked very much – Liked very much
3. Sedation (Not sedated – Very sedated)
4. Confidence in ability to drive safely (Not confident – Very confident)

This is a composite secondary outcome.
Timepoint [1] 320280 0
+1, +2, + 3.25, +5hr post drug administration
Secondary outcome [2] 320281 0
Cognitive Performance.

This is comprised of test performance on the following cognitive tasks:
Flankers task (measure of choice reaction time)
Digit-Symbol Substitution Task (measure of speed of information processing)
Rapid Visual Information Processing task (measure of alertness under cognitive demand)
Stop Signal Task (measure of ability to stop a planned response)
N-Back (measure of verbal working memory)

This is a composite secondary outcome.
Timepoint [2] 320281 0
+1, +2, + 3.25, +5hr post drug administration
Secondary outcome [3] 320282 0
Plasma cannabinoid concentrations, including includes measures of THC, THC-COOH, 11-OH-THC, CBD, and endocannanoids including 2-AG and anandamide.

This is a composite secondary outcome.
Timepoint [3] 320282 0
+1, +2, + 3.25, +5hr post drug administration
Secondary outcome [4] 320283 0
Oral fluid cannabinoid concentrations, incuding oral fluid of measures THC, THC-COOH, 11-OH-THC, and CBD.

This is a composite secondary outcome.
Timepoint [4] 320283 0
+1, +2, + 3.25, +5hr post drug administration
Secondary outcome [5] 331358 0
Mean speed and standard deviation of speed
Timepoint [5] 331358 0
+30 minutes, + 150 minutes post drug administration
Secondary outcome [6] 331359 0
Number of lane crossings
Timepoint [6] 331359 0
+30 minutes, +150 minutes post drug administration

Key inclusion criteria
(a) At least 18 years of age, and no more than 50 years of age
(b) Prior experience with cannabis (>10 lifetime exposures, <2x/week in previous 2 months)
(c) In possession of full Australian drivers license for at least 1 year
(d) Proficiency in English, and willing and capable of providing informed consent to the study procedures
Minimum age
18 Years
Maximum age
50 Years
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
(a) Any clinically significant prior adverse response to cannabis, cannabinoid products or synthetic cannabinoids, as assessed by an Addiction Medicine specialist (e.g. panic or other anxiety attacks, arrhythmia, falls, seizures)
(b) Cannabis dependence (ICD-10 criteria)
(c) A desire to abstain from cannabis use
(d) Past year mood or anxiety disorder (DSM-V criteria)
(e) Lifetime manic episode or psychotic illness (DSM-V criteria), or suspected family history of schizophrenia
(f) Interest in treatment for cannabis use
(g) Hypertension, cardiovascular disease, chronic pulmonary disease or asthma
(h) Under 18 years of age or over 50 years of age
(i) Use of medications that may impact upon the metabolism and excretion of cannabinoids (e.g. CYP450 enyzme inducers/inhibitors), or may impact upon driving ability (e.g. mood stabilisers, sedatives); and
(j) Pregnancy (primary plasma hCG screen in women of child bearing potential, confirmed with blood test if urine test positive) and women of child bearing potential must agree to using a reliable form of contraception during and one month after completion of the project.
(k) Required to complete drug testing for cannabis (e.g. workplace testing; court order)

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s
The people administering the treatment/s
The people assessing the outcomes
The people analysing the results/data
Intervention assignment
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)
Recruitment hospital [1] 5203 0
Royal Prince Alfred Hospital - Camperdown

Funding & Sponsors
Funding source category [1] 292788 0
Name [1] 292788 0
The Lambert Initiative for Cannabinoid Therapeutics at The University of Sydney
Address [1] 292788 0
Level 6
Brain and Mind Centre
94 Mallet St Camperdown 2050
Country [1] 292788 0
Primary sponsor type
The University of Sydney
The University of Sydney
NSW 2006
Secondary sponsor category [1] 291522 0
Name [1] 291522 0
Address [1] 291522 0
Country [1] 291522 0

Ethics approval
Ethics application status
Ethics committee name [1] 294278 0
SLHD Ethics Review Committee (RPAH Zone)
Ethics committee address [1] 294278 0
c/- Research Development Office
Royal Prince Alfred Hospital
Missenden Road
Ethics committee country [1] 294278 0
Date submitted for ethics approval [1] 294278 0
Approval date [1] 294278 0
Ethics approval number [1] 294278 0

Brief summary
Following the recent decision made by the Australian Commonwealth government to enable the cultivation of cannabis crops for medicinal grade products, it is likely that medicinal cannabis products – plant matter or extracts – will become more available in Australia in the years to follow. Various states including NSW are also investing in clinical trials of cannabinoid medicines for a number of debilitating illnesses, including the use of vaporised leaf cannabis products containing THC ( In will therefore become increasingly relevant, from a road safety and medico-legal perspective, to better understand the effects of these medicines on driving.

The psychoactive constituent of cannabis, THC, is only one of over 100 phytocannabinoids present in the Cannabis Sativa plant that may be promising therapeutic targets in medicine. CBD, for example, is a non-psychoactive cannabinoid with anti-inflammatory, neuroprotective antioxidant, anticonvulsive and antipsychotic properties. Preliminary studies suggest that in animal models CBD also modulates the pharmacological action of THC, dampening its psychotomimetic properties. The presence of phytocannabinoids other than THC (such as CBD) in some medicinal grade cannabinoid products distinguishes them from Australian street grade illicit cannabis, which contains very little to nil CBD. The presence of CBD could have important implications for the effects of cannabis-based medicines on driving.

Although other medicines such as benzodiazepines, opioids, and some antidepressants have been shown to impair driving ability, NSW law permits a person who is taking these medicines to drive so long as the drivers’ mental or physical faculties are not affected [9]. The current legal framework for driving under the influence of cannabis (where it is a criminal offence to be driving if THC is detected in saliva – with no functional assessment) reflects the illegal status of cannabis and predates the emergence of medicinal cannabinoid preparations.

The premise of the current proposal is to test the effects of a variety of medicinal cannabinoid preparations that differ in their concentrations of the cannabinoids THC and CBD. It is hypothesised that the impairing effects of THC will be modulated and possibly negated by the presence of CBD in medical grade cannabis. This study also seeks to test the efficacy of roadside testing equipment in discerning impaired from non-impaired driving. To establish if there are methods other than saliva testing that can predict driving impairment, this study will utilise an eye-tracking task, subjective measures and cognitive testing procedures.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 63082 0
Prof Iain McGregor
Address 63082 0
School of Psychology
University of Sydney
Building A18
NSW 2006
Country 63082 0
Phone 63082 0
+61 2 9351 3571
Fax 63082 0
Email 63082 0
Contact person for public queries
Name 63083 0
Mr Thomas Arkell
Address 63083 0
Room 243
School of Psychology
University of Sydney
Building A18
NSW 2006
Country 63083 0
Phone 63083 0
+61 2 9351 3433
Fax 63083 0
Email 63083 0
Contact person for scientific queries
Name 63084 0
Mr Thomas Arkell
Address 63084 0
Room 243
School of Psychology
University of Sydney
Building A18
NSW 2006
Country 63084 0
Phone 63084 0
+61 2 9351 3433
Fax 63084 0
Email 63084 0

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
What data in particular will be shared?
Individual participant data of published results only.
When will data be available (start and end dates)?
Immediately following publication, no end date.
Available to whom?
Only researchers who provide a methodologically sound proposal.
Available for what types of analyses?
For meta-analyses.
How or where can data be obtained?
Please contact the principal investigator (
What supporting documents are/will be available?
No other documents available
Summary results
Have study results been published in a peer-reviewed journal?
Journal publication details
Publication date and citation/details [1] 2876 0
Arkell, T.R., Lintzeris, N., Kevin, R.C. et al. Psychopharmacology (2019).
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary
Both active cannabis types increased lane weaving during a car-following task but had little effect on other driving performance measures. Active cannabis types impaired performance on the Digit Symbol Substitution Task (DSST), Divided Attention Task (DAT) and Paced Auditory Serial Addition Task (PASAT) with impairment on the latter two tasks worse with THC/CBD equivalent cannabis. Subjective drug effects (e.g., “stoned”) and confidence in driving ability did not vary with CBD content. Peak plasma THC concentrations were higher following THC/CBD equivalent cannabis relative to THC-dominant cannabis, suggesting a possible pharmacokinetic interaction.