Why medical cannabis patients should be allowed to drive

People who take cannabis containing delta-9-tetrahydrocannabinol (THC) for medicinal reasons are not allowed to drive, which can significantly affect their quality of life by restricting their freedom of movement.

Australia first introduced a regulatory framework allowing patients to legally access medical cannabis in 2016. Since then, the rate of prescribing has rapidly increased.

The approvals for access to medical cannabis via the Special Access Scheme Category B (SAS-B) alone exceeded 375 000, as of May 2023.

The SAS-B scheme allows health practitioners to apply for a permit to prescribe unapproved products to individual patients.

The majority of these prescriptions (~200 000) were for chronic pain, and most products prescribed were orally administered oils.

There have also been over 30 000 applications for patient access from 2035 prescribers via the Authorised Prescriber pathway.

Under current presence laws, which prohibit driving with a proscribed drug (in this case, cannabis containing THC) in one’s system, patients using medical cannabis products containing THC are banned from driving in each state with the exception of Tasmania.

These laws are enforced via roadside drug testing (RDT) that looks for the presence of THC and other drugs in oral fluid.

Although RDT is carried out in all Australian states and territories, Tasmania is the only jurisdiction where patients have a medical defence if they happen to test positive to THC and have a valid prescription for medical cannabis.

In Tasmania, driving with any detectable amount of THC is an offence, unless the product was obtained and administered in accordance with the Poisons Act 1971.

This restriction on driving has been the focus of several recent proposed legislative amendments.

In New South Wales, a Road Transport Amendment (Medicinal Cannabis – Exemptions from Offences) Bill was proposed in 2021 but rejected in 2022 due to concerns with perceived increase risk of road safety risk.

A similar bill – the Road Safety Amendment (Medicinal Cannabis) Bill 2023 — is now before the Victorian parliament and appears to have the support of the Premier.

What does the evidence say about medical cannabis and driving?

It is important to distinguish recreational cannabis laws and risks to driving compared with the prescribing of medical cannabis products containing THC prescribed by doctors for medical reasons.

Recreational cannabis contains unknown concentrations of THC with the aim to obtain a "high" from higher levels. This is not the aim with Medical Cannabis products.

Most of the international research on cannabis and driving is specific to THC. Cannabidiol (CBD), a non-psychoactive compound that is often found in medical cannabis, does not impair driving, and there is no restriction on driving for patients who are using CBD-only medical cannabis.

There is considerable dispute on the actual crash risk associated with driving with THC in one’s system. For example, a rapid review of the literature by Monash University concluded that “there is global consensus that the use of THC results in a range of impairments specific to driving, with these impairments being associated with an increase in crash risk”.

A separate Australian review also concluded that THC increases crash risk but noted that the magnitude of the increase is modest.

One of the most comprehensive reviews on the topic was conducted by members of the International Council on Alcohol, Drugs and Traffic Safety.

In 2021, over 20 experts from 11 different counties formed a Cannabis and Driving Working Group to address concerns around increasing cannabis use and implications for traffic safety.

The working group have since published a series of publicly available fact sheets that review the scientific evidence on cannabis and driving.

In one of these fact sheets, the working group reviewed the limited evidence that currently exists on the impact of medical cannabis (not recreational cannabis) on driving, quoting studies that show a nil impact or a reduction in fatal crashes in jurisdictions introducing medical-only access pathways.

In contrast, in jurisdictions where recreational cannabis was legalised or decriminalised, THC was associated with an increase in fatalities for some groups.

The quality of this evidence for the legalisation of recreational cannabis is generally good, as these studies use government data on crashes and hospital admissions, but it may be sometime yet before we have a clear picture of how changing cannabis laws have truly affected road safety.

It is important to distinguish recreational cannabis laws and risks to driving compared with the prescribing of medical cannabis products containing THC prescribed by doctors for medical reasons.

Ultimately, the working group concluded that “medical cannabis consumers should not be subject to THC zero-tolerance laws that make it illegal to drive with any detectable level of THC, as is the case with some other types of impairing medications, but they should still be subject to impaired driving laws.”

What would a patient exemption look like in practice?

A patient exemption from RDT for THC detection and the associated presence offence is not tantamount to giving patients the liberty to drive while impaired.

Any such change could bring medical cannabis (only when prescribed and used as directed) into line with other medications that can also impair driving, such as benzodiazepines and opioids, both of which appear to actually increase crash risk more than cannabis.

Patients would still remain vulnerable to impaired driving laws and the associated offence of driving under the influence.

Several international jurisdictions have already implemented policies enabling medical cannabis patients to drive so long as they are unimpaired.

New Zealand, for instance, recently passed legislation allowing oral fluid testing, but a medical defence is available to drivers who have taken medical cannabis in accordance with their prescription and are not demonstrating impairment during driving, such as lane weaving or failing to adhere to road rules.

Oral fluid testing was also recently introduced in Canada, but police must first have a reasonable suspicion, based on objectively discernible facts (eg, red eyes, speech patterns) that a driver is affected by a drug.

Other countries, including Norway, Germany, Ireland and the United Kingdom, also exempt patients from cannabis-impaired driving charges so long as they are unimpaired and were using their medication as prescribed.

What are some of the challenges to implementing a patient exemption?

There are several challenges that need acknowledging. For instance:

• what happens if a patient is combining prescribed medical cannabis with illicit cannabis?
• And how would police test for impairment if a driver does have a prescription but is demonstrably impaired?

The first of these two issues could be effectively managed through diligence at the point of prescription.

Doctors can and should inquire about previous cannabis and other drug use before prescribing medical cannabis.

If there are indications that a patient has a history of drug dependence or concurrent cannabis use, doctors might consider prescribing a CBD-only product without any THC or refusing access to medical cannabis.

Doctors can also use SafeScript and other real-time prescribing tools to identify patients who are currently prescribed other drugs of dependency (eg, benzodiazepines and opioids), and patients who might be “doctor shopping”.

SafeScript provides immediate alerts to the medical practitioner when trying to prescribe medical cannabis containing THC on top of other drugs of dependence. This is a very useful tool.

As outlined further below, a patient exemption might exclude certain groups of patients who already have an elevated crash risk, such as young drivers and people using inhaled products with high amounts of THC and/or alcohol.

The second issue, which relates to the determination of impairment, especially at a crash site, is one for which we already have a template.

Police can conduct what is known as a field sobriety assessment; this involves assessing a person’s balance, coordination, and overall behaviour.

Police can also look for signs of intoxication (eg, red eyes, speech patterns) and recent cannabis use (eg, smell of cannabis in the car).

If a police officer has a reasonable suspicion that a driver is impaired and intoxicated, then this may warrant an RDT for presence of THC, other illicit drugs, and alcohol in the body.

Research is currently looking at ways to improve the detection of impairment.

For instance, studies are looking at whether driver state monitoring systems might be able to identify alcohol and drug-related impairment in real time.

Driver monitoring systems devices help drivers, including across other areas of transportation such as aviation and rail, to provide real-time assessment of their capacity to perform the driving task.

Driver state monitoring systems are already widely implemented in modern vehicles to monitor fatigue and distraction, and they are mandatory for all new vehicles in the European Union.

What safeguards could be implemented to manage the risks?

Warnings about safe driving would potentially follow the same approach that doctors use when advising patients how to minimise the risk of impairment with any other potentially impairing medication.

For example, a label warning on the medical cannabis product can warn patients to avoid driving or using machinery if they experience sedation or drowsiness.

There are multiple safeguards that can be put in place from the point of prescription onwards to help minimise the risk of impairment associated with the use of THC-based products.

Examples derived from our own personal clinical experience include:

• Require patients to sign a consent form acknowledging the risk of side effects and contraindications to driving (eg, sedation, drowsiness) with THC-related products.
• Warn patients they cannot drive if impaired, just as we advise patients to not drive if impaired with pharmaceuticals such as benzodiazepines and opioids.
• Prescribe CBD-based products, which are non-intoxicating, first before considering the inclusion of THC, which can be intoxicating depending on the dose. Medicinal cannabis products contain a range of concentrations from CBD alone or CBD dominant, to a combination of CBD and THC of various ratios, to THC dominant products.
• Work from the principle of “start low, go slow”, titrating doses upwards slowly to use the lowest possible dose of THC, and avoiding THC altogether where contraindicated.
• Trial orally administered, low dose THC products before prescribing products for inhalation, as oral products can be dosed more precisely.
• Instruct patients to avoid driving for the first two to four weeks when initiating treatment with a THC-containing product, and avoid driving for at least 48 hours after each dose increment where the risk of impairment can increase (here, here and here).
• Instruct the patient to avoid driving for four to six hours after using inhaled products, and for eight to ten hours after ingesting oral products.
• Advise patients to avoid concomitant use of alcohol, other drugs of dependency, and illicit drugs that are known to increase the risk of impairment when used with THC-based medical cannabis products.
• Ensure prescribers have the authority to assess patients and prohibit driving if they believe a patient is unfit to drive.

It would also be wise to set parameters around which patients should be given an exemption, such as bus drivers, truck drivers, drivers in certain age groups more at risk of being involved in a crash, and drivers who already have alcohol or other drugs in their system.

The Victorian State Government has formulated useful recommendations based on existing driving guidelines that prescribers can consider when deciding on a patient’s fitness to drive.

Conclusion

At present, patients who take medical cannabis containing THC cannot legally drive in any Australian jurisdiction except for Tasmania.

An effective framework for allowing patients who take medical cannabis to drive is one that prioritises road safety while also recognising the importance of driving for freedom of movement and quality of life.

We believe it is possible to strike this balance, by drawing upon existing frameworks in other jurisdictions, providing warnings as doctors do with prescriptive drugs of dependency, and by establishing a set of risk-mitigating safeguards.

Dr Thomas Arkell is a Research Fellow at Swinburne University of Technology. His research focuses on the behavioural pharmacology of cannabis, including its effects on driving and cognitive function.

Associate Professor Vicki Kotsirilos AM is a medical practitioner, and Australia’s first Authorised GP Medicinal Cannabis Prescriber. Associate Professor Vicki Kotsirilos also served on the Medicinal Cannabis and Safe Driving Working Group, Department of Justice Victorian Ministerial Government committee from December 2020 to March 2021.

The statements or opinions expressed in this article reflect the views of the authors and do not necessarily represent the official policy of the AMA, the MJA or InSight+ unless so stated. 

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