Can Pharm J (Ott). 2019 Jan-Feb; 152(1): 10–13.
Published online 2018 Dec 12. doi: 10.1177/1715163518814273
Pharmacists should counsel users of medical cannabis, but should they be dispensing it?
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Canada has, since 2001, regulated the medical use of cannabis. To access medical cannabis, individuals must first obtain written authorization from a physician or nurse practitioner and then fax or mail the authorization form to a licensed producer, a commercial vendor approved and regulated by Health Canada. Licensed producers then ship the cannabis directly to the individual’s residence. Authorized individuals also have the option of cultivating cannabis for personal use. While Health Canada regulates the quality of the cannabis products available for sale (ensuring that they are not contaminated by mold or pesticide residue, for instance), there is no regulation of the levels of its 2 primary active ingredients, delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). Moreover, prescribers are not required to indicate the levels of THC and CBD on the authorization form, which is known as a “medical document.” Some patients therefore have some latitude in selecting cannabis potency.
A growing number of Canadians are accessing cannabis through the regulated system. In the last quarter of 2017, there were over 250,000 authorized cannabis consumers, and the number of users is increasing exponentially. Licensed producers shipped over 40,000 kg of cannabis to consumers in 2017.1
Recently, the Canadian Pharmacists Association (CPhA) urged the federal government to allow pharmacists to dispense medical cannabis.2 The CPhA argues that pharmacists are ideally situated to help patients manage their medical cannabis use. It is unclear if the CPhA proposes that pharmacies be the exclusive distributors of medical cannabis. However, a KPMG report commissioned by the association3 did propose this.
The proposal that pharmacists oversee patients’ cannabis use has much to recommend it. Pharmacists can help avoid potentially harmful interactions between cannabis and prescription drugs. In vitro and clinical studies indicate that inhaled cannabis and tobacco induce CYP1A2, with a synergistic induction effect, which could potentially lead to drug interactions and toxicities. This is especially true for drugs with a narrow therapeutic index.4 The literature indicates that Canadians who consume cannabis therapeutically use it primarily to manage pain and insomnia, as well as alleviate psychiatric symptoms (i.e., anxiety and depression).5-7 The demonstrated effects of CYP3A4 inducers and inhibitors on THC/CBD pharmacokinetics4 suggest that people currently on sedative psychotropic agents, opioids and benzodiazepines should be advised on potential drug interactions.
Second, it appears that a majority of regular medical cannabis users use THC-rich varieties; THC is the principal euphoriant compound in cannabis. While we have no data on cannabis prescribing patterns, there is indirect evidence to support this claim. We examined the product catalogs of licensed producers in May 2018 and graphed the levels of THC and CBD of each of the dry cannabis varieties available for sale (see Figure 1). Over three-quarters of the products available had THC levels in excess of 10%.
Dried cannabis sold by licensed producers, May 2018, by level of THC and CBD and cannabis strain
THC, delta-9-tetrahydrocannabinol; CBD, cannabidiol.
Regular use of high-THC cannabis can lead to psychoses,8 hyperemesis9,10 and dependence. Cannabis users have a lifetime risk of dependence estimated at 9%, rising to 25% to 50% among those who smoke cannabis daily.11 Cross-sectional studies demonstrate increased risk for development of substance use disorders in patients with substance use and a comorbid psychiatric disorder.12 Pharmacist-initiated interventions to reduce cannabis harms could be invaluable.
Finally, we have concerns over the use of cannabis in youth. The human brain continues to develop until the age of approximately 21 years.13,14 During this developmental period, the brain and endocannabinoid system14,15 are intrinsically vulnerable to the harmful effects of cannabis.13,14,16,17 Approximately 1 in 6 who initiate cannabis use in adolescence become addicted.4 Pharmacist oversight of the cannabis use of young people appears to be warranted.
While there is a sound rationale for pharmacist oversight of regular cannabis use, it is unclear if pharmacist dispensing of medical cannabis is the best route to achieve this. We see several problems.
First, the majority of regular users procure cannabis outside the regulated system18; many obtain cannabis from dispensaries, online vendors and other unauthorized channels. To give some perspective, Statistics Canada estimates that Canadians consumed approximately 773 tons of cannabis in 2017.19 The amount shipped to authorized medical cannabis users in 2017 was 40 tons or about 5% of the estimated total national consumption. Of course, some of this consumption is by infrequent users; such users likely do not require pharmacist guidance. However, a sizable share of the population consumes cannabis regularly. Our analysis of the Statistics Canada 2015 Canadian Tobacco, Alcohol and Drugs Survey (CTADS)20 found that about 5% of Canadians 15 years and older consumed cannabis either daily or weekly. Using the 2016 national population estimates, this works out to 1.8 million Canadians. The number of individuals enrolled in the medical cannabis access program is about 250,000, or only 14% of total regular cannabis users.
We could find no reliable data on the potency of the cannabis available outside of the regulated system. We therefore conducted a survey of online cannabis vendors. Figure 2 plots the levels of THC and CBD found in the product catalogs of the first 20 online vendors that appeared in a Google search of “online cannabis Canada.” Most of the cannabis varieties that we found contained high levels of THC. We also surveyed the cannabis varieties sold by 6 dispensaries (retail outlets) in the Toronto region. These varieties were also typically high in THC.