Medical cannabis 101: A discussion with Dr. Caroline MacCallum
Medical cannabis has been legalized in all but 14 states in the U.S. and its use for treating a range of conditions is a growing topic of conversation in the medical community. We talked with Caroline MacCallum, MD, a specialist in internal medicine, with expertise in complex pain and cannabinoid medicine. Dr. MacCallum is the medical director of Greenleaf Medical Clinic, where she has assessed and developed cannabinoid treatment plans for more than 5,000 patients using legal medical cannabis approved by Health Canada. She also is a clinical faculty member in the department of medicine at the University of British Columbia. Dr. MacCallum has published several articles in peer-reviewed medical journals and presented at numerous international conferences on topics related to medical cannabis.
Pinnacle Care (PC): Can you explain the basics of how cannabis works as a medical treatment?
Dr. Caroline MacCallum (CM): The endocannabinoid system is present in all animal species. This system has a number of functions, including regulating sleep, pain, and eating. It’s involved in several day-to-day metabolic processes that our body undertakes when it’s in good health. The main components of the endocannabinoid system are the CB1 and CB2 receptors. There are also natural chemicals produced in the body that mimic the effects of THC and CBD.
There are multiple strains or chemovars of the cannabis plant, including indica, sativa, and hybrids. In the plant, there are about 500 chemical compounds, some of which are active and some of which are inactive. The raw plant contains THCA and CBDA, which are the acids contained within the tricones (glandular or mushroom-like structures on the buds, which you can hardly see with the naked eye).
PC: Do patients have reservations about being treated with medical cannabis because of the stigma that some people associate with this medicine?
CM: Yes, patients have reservations about the use of cannabis. Cannabis has historically been stigmatized in our culture and that stigma makes people feel shame or guilt or feel hesitant to seek out this form of treatment.
When patients first see us, we always start with education about the plant so they see this is a medical tool, which we are using in an intentional way to achieve specific goals individualized to that patient. This approach helps patients feel more comfortable with the treatment.
PC: What is the medical evidence that supports the use of medical cannabis and for what conditions has it been shown to be effective?
CM: The best evidence and research for cannabis, where we have seen significant benefits, is for treatment of neuropathic or chronic pain, spasticity related to multiple sclerosis, chemotherapy-induced nausea and vomiting, and certain treatment-resistant seizure types, such as Dravet and Lennox-Gastaut syndrome. These are syndromes often found in children, which can be the cause of hundreds of seizures a day.
Many patients come in with symptom clusters, meaning they’re not just dealing with one diagnosis. For example, they may have cancer or pain, AND they also have trouble sleeping and are experiencing anxiety and depression. Cannabis can be useful in managing not only their main conditions, but also these secondary symptoms
PC: Why is it important to see a physician who specializes or is experienced in treating patients with medical cannabis?
CM: Cannabis is not a one-size-fits-all treatment. You can have very different experiences using cannabis on your own and using it under the direction of an experienced clinician. I find it helpful for patients to complete pain, anxiety, and quality of life questionnaires pre- and post-cannabis initiation. That way we have an objective way of tracking symptom response.
Different conditions require different types of plants and different routes of administration, such as inhalation vs. oral ingestion of oils or topical application to the skin. CBD, for example, is commonly used two to three times per day with minimal or no impairment. However, if a patient is using THC, I like to take advantage of the bedtime window, which allows us to minimize side effects. Starting with low dose THC and titrating slowly, tolerance to side effects can slowly develop. If necessary, we can also begin introducing low doses during the day as required for symptom control.
PC: Can medical cannabis cause side effects?
CM: There are some potential side effects, including anxiety, dizziness, dry mouth, and fatigue. More serious or rarer side effects include psychosis and panic attacks. Side effects are dose dependent. If you take a large dose of THC without testing your tolerance, you could experience some of the more severe side effects.
THC may not be suitable for those with unstable heart conditions or psychosis. However, CBD may be an option for these patients. It is important for anyone with multiple health conditions and potential drug interactions to be evaluated by a physician with cannabis expertise.
Emerging studies suggest than cannabis can help curb cravings for those with opioid or heroin addiction or serve as a potential replacement for people with substance use disorder. However, close monitoring and caution must be taken with these patients who are also at risk of cannabis use disorder. (Cannabis dependency or addiction is not common in individuals using less than 3 grams of dried cannabis or less than 40mg THC oil per day.)
Cannabis is just one tool in our toolbox. We are frequently adding cannabis as an adjunct to a person’s treatment plan rather than replacing other treatments with cannabis. It is also not a replacement for eating well and getting exercise. It’s part of a holistic approach to treatment.