Driving and Medical Cannabis

Different cannabinoids affect the body differently. Therefore, different ratios of cannabinoids in medical cannabis products will have varying effects. 

Research is underway in some Australian universities to determine if there is measurable level of cannabinoids in the blood at which driving capability is adversely affected. Until the results are released, the law cannot begin to be reviewed and changed.

Currently the Royal Australasian College of Physicians advises that anyone taking medical cannabinoids should not drive.

There are no legal driving restrictions for people taking prescription Cannabidiol (CBD) only medicines.

However, like many other medications, Cannabidiol (CBD) a non-psychoactive cannabinoid can cause drowsiness, fatigue and in some instances lowered blood pressure when first commencing the medication. These symptoms are observed more often when the CBD is taken at high doses or with another interacting medication so extreme caution is required when operating heavy machinery or driving.

In Australia, there is zero tolerance for driving with the presence of Tetrahydrocannabinol (THC) in oral fluid, blood or urine. Even if the driver has a prescription for medical cannabis, there is no legal defence for driving with even a trace of THC. 

THC can affect cognitive and motor skills necessary for safe driving such as attention, judgement, memory, vision and coordination.

Those taking medical cannabis need to be aware that THC can be detected in urine for many days after the last dose of medical cannabis. It can take up to five days for 80 – 90% to be excreted from the body. 

More research is needed in the area of driving and medical cannabis but so far the research has shown:

• vaporised cannabis containing THC can increase lane weaving and impair cognitive function in a driving simulator
• combining cannabis containing THC and alcohol dramatically impairs performance
• risks are greatest when a person first starts taking medical cannabis containing THC or if the dosage increases.

Unlike alcohol, a direct relationship between blood levels of THC and levels of driving impairment has not yet been established.