By Dr Janelle Trees, BSC (HONS), MBBS (HONS), FRACGP
When beginning any new medication, it’s important for a patient to consider its potential effect on driving or work. Driving and operating machinery could be affected by medicinal marijuana, especially when you are just beginning to use it. Any medication can affect a person in unpredictable ways. Let’s briefly review some of the issues related to cannabis-based medicines in this context.
- THC Affects Your Head.
Cannabis-based medicines are made from cannabinoids, active constituents of marijuana. The cannabinoids we now have available as medicines in Australia are THC (Tetrahydrocannabinol) and CBD (Cannabinidiol). Almost all medicinal marijuana is based on a combination of these two cannabinoids. The exception is regulated strains of natural marijuana leaf or flower, which also contain the many other cannabinoids (there are about seventy that we know). THC and CBD have different effects and varying proportions of the compounds are used to make different medicines with diverse uses.
THC is the cannabinoid which causes the psychoactive effects of cannabis. It makes people high, which is the major reason people use cannabis recreationally. This pleasurable effect can be a useful side effect or the main effect sought in using cannabis-based medicines for anxiety, addiction or some kinds of pain management. Because of this, some medicinal marijuana, including for pain management, is predominantly THC.
If your doctor, in consultation with you and perhaps another specialist, wants to try these THC-dominant medicines for your medical condition and gets permission to do so, you may need to be especially cautious about possible negative effects on your driving and work while your dosage and type of medicine is being worked out.
2. What Could Go Wrong?
Dizziness, drowsiness, low blood pressure and perceptual disturbances are all potential side-effects of a dose of marijuana which is too high.
Recreational users of medicinal cannabinoids are at increased risk of a fatal car accident or an industrial accident. When medicinal marijuana is prescribed, this risk is modified by control of dosage and regulation of the contents of the medicine. Prescribed medicine is always safer than the uncontrolled (and in Australia usually still illegal) herb. Medicinal marijuana is prescribed in lower doses than people take recreationally because the aim is to keep the patient in a steady state of being well.
While driving under the influence of cannabis is a clear public danger, most of the information we have about it is from recreational users of cannabis who have had accidents, people who tend to combine their cannabis use with alcohol and to take much larger doses of both substances to intoxicate themselves.
- What about CBD-based medicines?
Side effects may be milder with CBD-based medicines. They are particularly useful for people who have had previous experience of unpleasant effects from THC in marijuana—feeling out of control, paranoid or panicked. CBD itself does not have psychoactive effects. Some patients find the effect of CBD-based medicines quite subtle when they begin taking it.
Medicines in which CBD predominates have anti-inflammatory and anti-spasmodic effects. They can be useful in managing pain, nausea and anxiety.
- How do we go ahead, then?
Like many medicines, cannabis-based medicines need to be commenced at the lowest practical dose. After a trial of this low dose, perhaps over three or four days, the dose can be increased by small increments to find the smallest effective dose. During the time that a new dose is being started patients need to be cautious about driving, operating machinery or other tasks which could be affected by unwanted side effects. Be alert for feeling unwell and be informed of the potential side effects, just as you would for any other new medicine. You might even choose to plan the start of your new medicine or higher dose so that you can take it easy and concentrate on how the medicine is affecting you, for example, starting the higher dose or different med on your day off.
This kind of regime is familiar to anyone who has taken opiates for pain relief (like Oxycodone), psychoactive drugs (eg antidepressants) or anticonvulsants (for epilepsy or neuropathic pain). Think about whether you will need time off work (depending what your responsibilities there are) and if you have to go to work, consider asking a friend to drive you or using public transport. Think about what you would do to protect yourself (and others) if you suffer adverse effects from the medication.
- What about drug testing?
If you work for an employer who enforces a drug-free workplace by regular or random drug screening, you will need to consider how a positive screen for THC will affect your work situation. This is possible even when you take strongly CBD-based medicine, as a trace of THC is likely to be present. If your employer is aware of your medical condition and the cannabis-based medications make you a better worker, there may be room for discussion. Be aware, though, that some occupations or workplaces may not yet have experience with workers taking medicinal cannabis. If you work in the armed forces, in aviation or mining, for example, it is likely that you will not yet be permitted to use this medicine and continue in your usual role. Be cautious and investigate your circumstances before you apply to be allowed to use this medicine. Talk to your doctor, who may refer you to a colleague who specializes in occupational health.
The point of taking marijuana-based medicines is to become more functional. If you have uncontrollable pain, or seizures or anxiety or whatever the medicine treats, the symptoms of your illness can greatly impair your ability to drive or work. Your doctor’s aim, working with your medical team and perhaps the advice of an Australian medical marijuana clinic, is to get you onto a steady regular dose of medicinal marijuana medicine with predictable, beneficial effects.