If your patient is one of the thousands of Australians who have received a prescription for medicinal cannabis, there are rules, risks, and restrictions in place to keep them (and other drivers) safe on the road.

It’s important that your patients are aware of these rules, especially if they have been prescribed a treatment that contains THC.

Throughout this article, we’ll outline these existing rules and restrictions and provide ways to support your patients’ safe driving practices while taking medicinal cannabis treatments. 

Should your patients drive while taking medicinal cannabis? 

Because no two patients are the same, the question of whether or not your patients should drive while taking medicinal cannabis treatments will also vary from patient to patient. In Australia, it is legal for medicinal cannabis patients to drive as long as there is no detectable amount of THC in their system. 

However, there are a few other things your patients should consider when deciding whether or not to drive while taking their treatments. 

Impairment 

Any time your patient takes their prescribed (non-THC) medicinal cannabis treatments (or any other medication or legal substance that has an effect on the mind and body), they should wait until they are confident that they are safe to drive and are not experiencing any impairment or adverse side effects before doing so. 

Even though it is not illegal for medicinal cannabis patients to drive with CBD in their system, it is important that they don’t get behind the wheel while impaired by any substance. Encourage your patients to consider whether it is safe for them to drive before doing so, and advise them to wait until the effects have worn off before they drive. 

Some symptoms your patients should be mindful of before getting behind the wheel include: 

  • Dizziness 
  • Low blood pressure 
  • Drowsiness 

Testing positive for THC

The most important restriction for medicinal cannabis is that even with a valid prescription, it is currently illegal, in all Australian states and territories except Tasmania,  for patients to drive with any amount of THC in their systems 

If you have prescribed a patient a medicinal cannabis treatment containing THC, this will mean that they will need to wait until the medication has left their system before they are allowed to drive. The amount of time cannabis can stay in a person’s system can vary from patient to patient and can be dependent on factors like: 

  • The type of treatment consumed 
  • The amount of THC present in the treatment 
  • The method the patient used to consume the medication 
  • The frequency with which the patient consumes their medication’

With the above points in mind, if your patient consumes a medication containing THC and tests positive for THC in a mouth swab test, they can lose their licence – even with a valid prescription.

Detection Windows by Test Type (read on for further details on detection windows):

  • Urine Test: Most common for workplace drug testing. Detectable for 3-30 days.
  • Blood Test: Used less frequently; detects THC for 1-2 days (longer for heavy users).
  • Saliva Test: Common for roadside testing; detects THC for 1-3 days.

Is it legal for patients to drive while taking CBD? 

CBD-containing medical cannabis treatments that do not contain any THC are legal for a patient to have in their system while they drive. Your patients should always know which cannabinoids are in the cannabis treatments they are prescribed and understand the driving restrictions that exist for those treatments as well as the effects they may experience when consumed. Some CBD treatments – like CBD oils – do contain THC, while others don’t. 

Even if a prescribed treatment doesn’t contain any THC, encourage your patients to pay attention to the effects they may experience while taking their medication to ensure they aren’t driving while impaired. While CBD tends to have a minimal side effect profile, it can cause side effects like drowsiness and fatigue in some patients. 

We recommend speaking to your patients about the importance of ensuring they feel safe, alert, and confident before getting behind the wheel and waiting for side effects to wear off before they start driving. 

Is it legal for patients to drive while taking THC?

No. It is not legal for patients to drive with any amount of THC in their systems  in all states in Australia (except Tasmania), even if they are medicinal cannabis patients with a valid prescription. If a patient chooses to consume products containing THC and does not wait long enough for the THC to leave their system, they are at risk of losing their licence if they test positive for THC in a mouth swab test. 

These laws exist because THC is a psychoactive cannabinoid which can affect cognitive and motor skills that are needed for safe driving, including attention, judgement, vision, coordination and memory. However, because THC can be detected in the body for up to weeks after the initial consumption, these laws can unfortunately unfairly discriminate against legal medicinal cannabis patients who may face fines and loss of their licence even when they are unaffected and unimpaired by their medication at the time of testing. 

In fact, cannabis is the only legally prescribed medication for which you lose your licence when testing positive for presence, not impairment (except in Tasmania). Tasmania is the only state in Australia that allows unimpaired drivers who have been legally prescribed medicinal cannabis to lawfully drive.

How does medical cannabis affect driving?

Any substance that has an effect on the mind and body is capable of affecting a person’s ability to drive. This is true of both legally prescribed and recreational substances, as well as both plant-based and standard treatments.

Any time a patient begins taking a new medication, or has changes made to their treatment plan or dosage, we recommend that they wait to ensure they are not experiencing any effects or side effects that may impact their ability to drive before getting behind the wheel. 

When it comes to measuring cannabis impairment, science tells us that there are several factors which play a role – including dose, mode of ingestion, length of treatment and individual factors like weight and metabolism.

In 2020, a landmark study led by the Lambert Initiative for Cannabinoid Therapeutics at the University of Sydney and conducted at Maastricht University in the Netherlands found that CBD does not impair driving, while moderate amounts of THC produce mild driving impairment lasting up to four hours.2

A 2022 study led by the same group found that 1500mg, the highest daily medicinal dose of cannabidiol (CBD), has ‘no impact on people’s driving or cognitive abilities.’3

The results from these studies reassure us that patients using CBD-only products are most likely safe to drive, and help us understand the duration of impairment for patients using THC-dominant products. But since driving laws in Australia use a zero-tolerance policy for THC in drivers, the law still dictates that patients consuming THC should not be driving.

Another 2022 study4 conducted by researchers at the University of Sydney’s Lambert Initiative which analysed all available studies on the relationship between driving performance and concentrations of THC in blood and saliva found ‘blood and oral fluid THC concentrations to be relatively poor or inconsistent indicators of cannabis-induced impairment.’ This is in contrast to the much stronger relationship that can be seen between blood and alcohol concentrations and driving impairment.

‘Higher blood THC concentrations were only weakly associated with increased impairment in occasional cannabis users while no significant relationship was detected in regular cannabis users.’ – Lead author Dr Danielle McCartney, Lambert Initiative for Cannabinoid Therapeutics 

So while this research does not suggest there is no relationship between THC intoxication and driving impairment, it does call into question the validity of the methods used to assess cannabis-related impairment in drivers in Australia. This highlights the need for more reliable methods of assessing cannabis-impairment in drivers and a reform of the cannabis-driving laws which unfairly impact patients who are using legal medicinal cannabis products who cannot currently drive, even when they are not impaired.

The findings of this study were reported on The Project, Network 10:

DRUG DRIVING DISCOVERY - The Project Network 10As of May 2024 the Victorian State Government has partnered with Swinburne University to conduct the first Australian medicinal cannabis driving trials where participants who have been using medicinal cannabis for a minimum of 6 months will undergo a series of driving tests in a controlled closed circuit track. The study will go for 18 months and will monitor how participants are affected pre- and post-cannabis administration. Hoping to use this data to implement safe and effective driving laws while also providing important information to Healthcare professionals when it comes to medicinal cannabis.

How long after consuming medicinal cannabis is it safe for a patient to drive?

If your patient consumes a medicinal cannabis product containing no THC (such as a CBD-only oil), then it is safe for them to drive – provided that they are not experiencing any adverse side effects like dizziness or low blood pressure. 

When consuming CBD-only products, patients only need to wait until they are certain they are no longer experiencing any side effects that may impact their driving. CBD-only products will not show up on a drug test, and it is legal for patients to drive after taking them. 

If your patient consumes a medicinal cannabis product containing THC, the answer to this question is a little more complicated. Because it is illegal for a person to drive with any amount of THC in their system, and because the amount of time it takes for THC to leave a person’s system varies so much from patient to patient, there is no definitive answer to how soon a person can drive after consuming THC. 

While the above research tells us that the impairing effects of THC fade after four hours of having consumed it, Australian police test for THC presence, not impairment, when drug testing drivers. So, it’s important that your patients understand how long cannabis can stay in their system before driving. 

How long does cannabis stay in a patient’s system?

Unfortunately, there is no definitive answer to this question, as it varies from individual to individual depending on a range of factors, such as:

  • The amount of THC / cannabis consumed
  • How often your patient consumes cannabis
  • Your patient’s body fat percentage
  • Your patient’s metabolism
  • How much exercise your patient does
  • The type and sensitivity of the drug test taken

Generally, random roadside saliva tests can detect THC for about 12 hours5 after use in people who use cannabis less frequently. But for those who frequently use cannabis, such as medicinal cannabis patients who use cannabis to help treat chronic conditions, THC can usually be detected for around 30 hours5 after use. Again, these numbers will vary from person to person.

For other types of drug tests, which may be required in certain workplaces or other settings, cannabis can be detected in a person’s system for even longer, including up to 6 days for blood tests,6 up to a month for urine tests5 and up to 3 months for hair tests.7 

Because it is so difficult to know when and if a patient might legally be able to drive after consuming THC, if your patient has to drive frequently for work or other activities, you may want to encourage them to consider a CBD treatment rather than a THC one under the current driving laws in Australia. 

Driving and cannabis law reform in Australia through Drive Change

Drive Change is an Australian law reform campaign fighting to give medicinal cannabis patients the same rights as other patients. They are a team of educators and advocates who believe that current drug driving laws ‘fail to improve road safety, discriminate against medical cannabis patients and impede public health outcomes.’

Drive Change proposes equal rights for legal medical cannabis patients through the following solution:

‘The government implements Australia-wide uniform drug driving laws to allow for a complete defence to the presence of THC in a driver’s oral fluid or blood when:

  • The driver has a valid doctor’s prescription for a medicine containing THC
  • The offence does not involve dangerous or reckless driving; and
  • An officer cannot establish driver impairment.’

Visit Drive Change to learn more about how you can support the campaign and help create equal driving rights for legal medical cannabis patients.

How to support your patients in understanding the cannabis driving laws in their state

If a patient approaches you with questions or concerns surrounding medicinal cannabis driving laws, the below resources contain state-specific information regarding the driving laws in each state: New South Wales

Queensland

Victoria

South Australia

Western Australia

Tasmania

ACT

NT

The bottom line

It can be difficult for medicinal cannabis patients to know whether or not they should drive. But no matter what their situation is, they should never drive while impaired. Patients who take THC-free / CBD-only medicinal cannabis products can safely and legally drive provided they are not experiencing any adverse side effects that might impede their driving ability. However, patients taking THC medicinal cannabis products can face fines and even the loss of their licence if any amount of THC is detected in their system in a roadside test.

It is important that both the prescribing doctor and patient are aware of the cannabinoids and ingredients in the prescribed treatment, and are familiar with any driving restrictions that may exist for that treatment within their state or territory. 

Help create equal driving rights for legal medical cannabis patients by visiting Drive Change.

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