Plant medicine and driving is complicated. As with most aspects of plant medicine , driving is not a one size fits all approach. As this recent research study points out, there is little consensus on the degree and duration of impairment typically seen with plant medicine use.

Effect on Driving

A recent systematic review concluded that: In general, cognitive performance declined mostly in a dose-dependent manner, with a steady decline of impairment in the hours following administration. Doses were lower than those typically reported in recreational studies.

In all the studies, there was no difference between any of the medication groups and placebo on any neurocognitive measure after 4 h of recovery. Variability in the dose-dependent relationship raises the consideration that there are other important factors contributing to the duration of neurocognitive impairment besides the dose ingested.

What this review suggests is that impairment duration from ingesting plant medicine is greatly dependent on the individual person taking the medication. It also suggests that for plant medicine users, any impairment disappears after 4 hours, indicating the users are taking lower doses than recreational users.

Medically Prescribed Plant Medicine

There are a vast number of  products and types that can be prescribed by your doctor. These products can come in the form of oils, sprays, capsules and more.

If you are prescribed plant medicine containing psychoactive substances, then it is illegal to drive. This is because a psychoactive compound affects cognitive and motor skills that are necessary for safe driving. Such skills that are affected include attention, judgement, memory, vision and coordination. The substance can also be detected in the body for weeks after initial consumption. This unfortunately means users can face fines and loss of their licence despite being unaffected by the drug at that point in time.

As compared to black market products, you would never know how much psychoactive substance there is in a product and the concentration can be wildly inconsistent from batch to batch. It is far safer and even potentially cheaper to use medically prescribed plant medicine in Australia.

Plant Medicine & Crash Risk

Older research suggests that positive tested drivers are 1.1 to 1.4 times more likely to be involved in a crash. They are also found to be more liable for a crash. However other recent studies indicate that no significant increases in crash risk occurs with use, especially when the concentration is low in the blood.

In a recent survey of Australians, most respondents (72%) believed that their medical plant medicine use does not impair their driving. A similar percentage (71%) reported that their medical use does not affect their ability to assess their fitness to drive. Just over one-third (35%) of respondents reported typically driving within three hours of use. These findings highlight a need for patient education regarding the risks associated with driving under the influence of plant medicine. Be sure to discuss these risks with your doctor or GP when undergoing treatment.

Mobile Drug Testing

All Australian jurisdictions carry out random mobile drug testing (MDT), similar to random breath testing for alcohol. If roadside tests are positive, your oral fluid is then subject to further analysis in government laboratories. The three drugs that are usually tested for are THC, methamphetamine (crystal meth) and 3,4-methylenedioxymethamphetamine (MDMA), with cocaine also tested for in NSW. MDT only tests for the presence of drugs and not for impairment, and that driving with the presence of an illicit drug (i.e., ‘mere presence’) is a separate offence from driving under the influence.

Legal plant medicine is not a valid defence against prosecution under MDT laws, and patients face potentially severe penalties for driving with legal medication products in their system. This is a major barrier for patients contemplating or receiving plant medicine treatment. In particular, patients who live in remote areas who depend on being able to drive for their employment and quality of life are most affected.

Click here to read more about the penalties and possible consequences of driving under the influence of THC.

Plant Medicine Detection Times

The psychoactive substance is typically detectable in your oral fluid for 4 to 6 hours after smoking or vaporising it. This however is highly variable across individuals and depends on factors such as frequency of use. In blood, it is commonly detectable for up to seven days, and in extreme cases, for up to 30 days. In urine, it may be detectable for up to 24 days, depending on the sensitivity of the test.


Any substance that interferes with the complex task of driving can be dangerous. Plant medicine in general can have a more pronounced impairment on driving and should be handled with caution. Although some plant medicine products appear to have no significant traffic safety risk, it is best to consult with your doctor first before deciding to drive while undergoing treatment. For more information, feel free to read this research article that reviews the evidence regarding plant medicine and driving impairment. If you would like to book in a consultation with one of our doctors click here.