Can I drive when taking medicinal cannabis? Is it safe?

Your doctor has just prescribed medicinal cannabis. You think it’s helping. But you rely on your car to get to work and pick up the kids.

Are you allowed to drive? And more importantly, is it safe?

Here’s what the evidence says and what it means for you.

Medicinal cannabis is now widely prescribed in Australia for conditions such as chronic pain, anxiety and sleep disorders.

You can take it in a variety of different ways – for instance, by inhaling it using a vaporiser, or by ingesting an oil. There are many different active compounds. However, the main ones – known as cannabinoids – are delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD).

THC is also the intoxicating part of cannabis that gets you “stoned”. So this is where things get complicated.

What happens when you take medicinal cannabis?

When cannabis is inhaled, the effects peak in the first hour. They taper off over two to three hours, but can last for up to four to six hours.

When taken orally – for example as an oil – the effects don’t start straight away and can last for up to 8 to 12 hours. That’s because the cannabinoids are absorbed by your gut and metabolised more slowly.

THC negatively impacts cognitive functions, such as attention and memory. It impairs driving in a simulator and in the real world on a highway.

The effects of THC on driving are roughly comparable to low blood alcohol concentrations. But this depends on the dose and how often someone uses cannabis.

Medicinal cannabis used for insomnia does not cause impairment the next day, and regular cannabis users show no driving impairment after 48 hours or more of abstinence.