Information for patients: driving and medical cannabis in New Zealand

What medical cannabis patients in New Zealand need to be aware of when it comes to driving, impairment and roadside saliva tests.

Patients in New Zealand need to be aware of how their medicinal cannabis could impact their driving ability. One of the most important aspects of driving is cognitive functioning—the ability to pay attention, process information, and make decisions quickly. Obviously, if your cognition is impaired in any way, your driving will be affected as well. Some prescribed medications, including THC-containing medicines, can cause cognitive impairment and therefore impair driving ability.

If you have been prescribed medical cannabis, some key things to keep in mind when driving include understanding your dosage and response to the medication, understanding the effects of different strains and CBD vs THC, and being aware of any possible drug interactions or side effects.

In this blog, we will provide general advice for medical patients. If you are unsure how your specific medication might affect your ability to drive safely, it is best to speak with your doctor or healthcare provider for guidance.

How medical cannabis affect your ability to drive

Driving while under the influence of medical cannabis can be dangerous. While medical cannabis may help people manage chronic medical conditions, it’s important to remember that these medicines can produce side effects such as drowsiness, impaired judgment and slower reaction times that may make driving unsafe. Medicines containing THC are more likely to cause impairment and affect your driving. As always, it is best to consult with your physician about when it is safe for you to drive after taking your medicine.

How Cannabinoid Oil affects driving ability

Cannabidiol or CBD, is a compound found in cannabis plants. Unlike THC, CBD oil does not produce psychoactive effects. This means that it cannot make you "high" but it can still make some patients feel drowsy.

Of the limited studies assessing the effects of CBD oil on driving ability, the current evidence suggests that CBD oil at therapeutic doses does not cause driver impairment. One study showed that patient driving ability was not affected, even at high doses of 1500mg. Another study assessed how vaporised cannabinoids impact driving ability and found no significant difference between cannabinoid-dominant medicines and the placebo. However, the study did show that THC-containing medicine impairs driving ability skills and increases lane weaving.

When is it safe to drive after consuming THC?

The amount of THC in your system, the method of consumption and your tolerance to the medicine will determine how impaired you are. For example, if you've only consumed a small amount of THC-containing medicine, you may only be slightly impaired and the effects may subside in the next 2-3 hours. However, if you've consumed a large amount or if you have a low tolerance for THC, you may be significantly impaired and feel the effects for longer.

It's important to note that the effects of THC can last for several hours after consumption. This means that even if you consume your medication early in the day, you may still be impaired later on. For this reason, it's always best to err on the side of caution and wait at least 6 hours after consuming THC before getting behind the wheel.

Factors That Affect How Your Body Metabolises THC

Everybody metabolises THC differently; some people may feel the effects for several hours while others may only feel it for 1-2 hours. There are a few factors that can affect how your body metabolises THC, including:

  • Your individual physiology
  • The amount of food in your stomach
  • The strength of the strain
  • How frequently you consume your medicine

If you're unsure about how long the effects of your medication will last, it's always best to first try your medicine on a day you will not need to drive. And remember: it's never worth risking your life or the lives of others by getting behind the wheel while under the influence of any prescription medicine or illicit substance.

Tips for staying safe on the roads when using medicinal cannabis

Start low and go slow

When trying medicinal cannabis for the first time, it is important to start with a low dose and go slow. It can take up to two hours for the effects of the medicine to be felt, so it is important to start small and increase your dose gradually. Get familiar with how long it takes for the effects of your medicine to subside before driving anywhere.

Avoid mixing with other substances

Inform your doctor about any medications you take. Some prescription medications and supplements can interact with cannabinoid medicines and increase impairment.

Consult your doctor

If you plan on using CBD oil or THC, it's important to get a prescription from a doctor first. A doctor can help you determine whether or not these substances are right for you and provide guidance on how to use them safely.

What does New Zealand law say?

In New Zealand, the laws for Medicinal cannabis and driving are no different than any other prescription medication that has the potential to cause impairment.

It is up to the police officer to determine whether the driver is in fact impaired. If you are using a CBD isolate medicine without THC, it is unlikely you will test positive at all.

So long as you have a legal prescription for your medicine and you are not impaired while driving, you do not need to be concerned about roadside saliva testing. If you’re not impaired but still test positive, you should not get in trouble as medicinal patients in New Zealand have an exemption under Section 16 of the Land Transport (Drug Driving) Amendment Act 2022.

What happens if I don’t have a legal prescription?

As medicinal cannabis becomes increasingly accepted by medical professionals and the general public, it's important to keep in mind that if you don't have a valid and legal prescription from your doctor, it won't be recognized as medical treatment. In the eyes of the law, medicinal cannabis without a legal prescription will be treated like any other illicit substance. If you believe medicinal cannabis could help alleviate your symptoms and improve your quality of life, make sure to discuss it with your doctor and find out what your options are.