FAQs: Medical Cannabis Information

This section features answers to frequently asked questions, by healthcare professionals, about medical cannabis treatment options for patients.

Which medical conditions has medical cannabis shown efficacy for?
Clinical research has shown efficacy for Epilepsy, Spasticity (Multiple Sclerosis), Chronic Non-Cancer Pain, CINV anti-emetic & Palliative care. There are many ongoing trials to study medical cannabis for other medical conditions.
What common conditions and symptoms do Harvest Medicine patients note that medical cannabis has been helpful in managing?
The most common medical conditions patients seek consultations with us for are: arthritis, anxiety, cancer treatment side effects (such as nausea induced vomiting), chronic pain, depression, fibromyalgia, insomnia, irritable bowel syndrome, multiple sclerosis, & sleep disorders. Visit our patient reported outcomes for additional information about how medical cannabis has improved symptom management and/or quality of life for our patients.
What is the difference between CBD & THC?
THC, Tetrahydrocannabinol, is the psychoactive component of cannabis, in that it creates the feelings of euphoria and impairment that are traditionally associated with cannabis usage. Patients report that THC may be helpful as an appetite stimulant, sleep aid, and with mood disorders and pain relief. CBD, Cannabidiol, is the second most common active cannabinoid. It is considered to be non-impairing with anxiolytic, anti-seizure, anti-inflammatory, & pain relief properties.
Are there any contraindications for medical cannabis?
Yes. THC is the most prominent for contraindications, but there a few for CBD as well. Cannabis is metabolized by CYP450: therefore, CBD and THC should be assessed the same way as medications causing concern as inducers and inhibitors of cytochrome P450. General contraindication categories are cannabis allergies, known substance abuse, psychosis, cardiovascular disease, operating heavy machinery, pregnancy, breastfeeding, & < 25 yrs (On a case by case basis, certain conditions may be evaluated for CBD treatments, given consent from the patient’s specialist(s) healthcare team).
What are the most commonly experienced side effects?
Dry eyes and mouth, increased appetite or weight loss, increased appetite or weight loss, drowsiness and fatigue, feeling faint or lightheaded, headache, diarrhea, impaired memory, increased risk of falls, disturbances in attention and concentration. Patients using products high in CBD & low in THC concentrations will generally experience fewer side effects than when only consuming highly concentrated THC products. Note that certain side effects may be beneficial for symptom management. For example, a patient with a sleep disorder or who cannot sleep due to pain will benefit from the sedative properties of cannabis. Reactions to medical cannabis vary from individual to individual however, some key differentiating factors include the route of administration, metabolization, strain type, cannabinoid concentrations, and quantity consumed.
What are the short and long-term side effects of CBD & THC?
Experienced side effects from THC & CBD will depend on the quantity consumed, method of intake, & individual sensitivities. The short-term effects of THC may include drowsiness, fatigue, dizziness, dry mouth, confusion, feeling high, euphoria, psychomotor impairment, tachycardia, arrhythmia, BP disturbances, acute psychosis, and hallucinations. Long-term effects of THC may include worsening anxiety and depression, the possibility of exacerbating pre-existing schizophrenia, amotivational syndrome, risk of cannabis hyperemesis syndrome, chronic bronchitis cough, wheeze, sputum, and fetal exposure is teratogenic. CBD tends to have low toxicity overall and is well-tolerated. The long-term side effects of CBD are not fully characterized but may include weight changes and abnormal LFTs, however, short-term experienced side effects may include drowsiness, fatigue, decreased appetite, diarrhea, dry mouth, and sleep disruptions.
What are its effects on the brain? What are its effects in the developing brain?
Long-term, CBD may be neuroprotective. Depending on age and length of use, THC can cause abnormal brain development and limits in functioning. Short-term, THC can cause memory impairment, decreases in concentration and executive function.
How long does cannabis remain active in the body and how do routes of administration affect bioavailability? 
When cannabis is consumed by inhalation, it has a rapid-acting onset within 5-10 minutes with experienced peak effects at 10-20minutes. The duration of action is 2-4 hours, while it may remain for up to 24hrs. Factors that influence plasma concentrations are depth of inhalation, puff duration, and breath hold. If cannabis is consumed by ingestion the onset is delayed at 0.5-3 hours and has long-acting effect that remain active for 6-8 hours (up to 24 hours). Factors influencing plasma concentration are fasted/fed state (there is higher absorption when taken with healthy fatty food), vehicle (oil, extract, edibles), and physiological factors such as a GI disease. Although wide variability exists regarding time to onset and peak effects of oro-mucosal and intranasal administration, peak plasma concentrations have been found at 2-4 hours. Rectal administration bypasses the first-pass metabolism which can result in higher bioavailability than the oral route and peak plasma concentrations have been found at 2-8 hours. Topical applications require transport across the aqueous layer which is a rate-limiting step in the diffusion process and systemic absorption is expected to be slow with a large Tmax.
After administration, for how long are metabolites detected?
A study by Alain G Verstraete, in 2004, on the detection times of drugs of abuse in blood, urine and oral fluid shows that “the detection times depend mainly on the dose and sensitivity of the method used and also on the preparation and route of administration, the duration of use (acute or chronic), the matrix that is analyzed, the molecule or metabolite that is looked for, the pH and concentration of the matrix (urine, oral fluid), and the interindividual variation in metabolic and renal clearance. In general, the detection time is longest in hair, followed by urine, sweat, oral fluid, and blood. In blood or plasma, most drugs of abuse can be detected at the low nanogram per millilitre level for 1 or 2 days. In urine, the detection time of a single dose is 1.5 to 4 days. In chronic users, drugs of abuse can be detected in urine for approximately 1 week after last use, and in extreme cases even longer in cocaine and cannabis users. In oral fluid, drugs of abuse can be detected for 5-48 hours at a low nanogram per millilitre level.”
How do urine/ saliva/ blood tests for cannabis work?
Companies such as Cannabix are actively pursuing new cannabinoid detection tools to help determine recent use and impairment. These tools will be useful for law enforcement for early detection at roadside check stops and to confirm impaired driving. To detect THC, Cannabix utilizes high-field ion mobility and mass spectrometry in a diverse portfolio of breath testing technologies. Visit the Department of Justice online for additional information on impaired driving laws, including cannabis (THC), in Canada.
Is it addictive? How does it compare to opioids & be utilized for opioid reduction?
Research has shown that cannabis has less addiction potential than opiates; with fewer potential long term, harmful side effects and reduced withdrawal symptoms. A 2019 study shows promising evidence that cannabis could be beneficial for opioid reduction as part of a harm reduction strategy. Evaluation of the Effects of CBD Hemp Extract on Opioid Use and Quality of Life Indicators in Chronic Pain Patients: A Prospective Cohort Study (2019); in which over 50% of the participants using the cannabinoid extract were able to reduce opioid medications at week 8 with other polypharmacy reductions. There is still a need for more well-designed placebo-controlled RCTs assessing CBD’s effects in managing opioid use disorders to confirm efficacy and safety.
How are products standardized to provide consistent dosing to patients?
Licensed producers follow GPP, GMP, or EU-GMP regulations to ensure the consistency and safety of medical cannabis products. At the end of manufacturing processes product sampling for potency and contamination is completed by a third-party lab, with a COA (Certificate of Analysis) issued. If cannabinoid content, mould, pesticide and heavy metal content fall within the limits set by Health Canada guidelines, it is deemed safe for consumption and can be packaged for sale. Product stability programs are also in place to confirm that potency remains within the set tolerance.

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