Herbal marijuana is not an approved drug in Canada, but court rulings have required reasonable access to a legal source of marijuana when authorized by a physician. On April 1st, Canada’s current regulatory system for medical marijuana will be replaced entirely by a new set of rules. These new regulations will have important implications for both doctors and patients.
For information on what patients need to know about medical marijuana, read Healthy Debate’s Personal Health Navigator article: Hazy Evidence on Medical Marijuana Use .
This article explores what doctors should know about the new rules for herbal marijuana for medical purposes, including the evidence for its use, available alternatives (including pharmaceutical cannabinoids), and the position of regulatory bodies such as the College of Physicians and Surgeons of Ontario. This article focuses on the use of marijuana to treat chronic pain, which is its most common therapeutic use (other potential uses not covered by this article include treatment for spasticity, anxiety, insomnia and nausea).
Note: in this article, the terms “marijuana” and “herbal marijuana” are used to describe the cannabis plant, usually dried and then consumed by smoking. The term “pharmaceutical cannabinoids” is used to describe approved medications that either mimic or contain active ingredients found in the cannabis plant.
Canada’s new rules for medical marijuana
Under the old regime, doctors who believed their patients might benefit from herbal marijuana for medical purposes signed a declaration to Health Canada, attesting that alternative therapies had been attempted or considered, but had either failed or were inappropriate. Under this system, the authority of whether to grant permission to use marijuana rested with Health Canada. Patients who were granted permission to use marijuana for medical purposes had the option to grown their own, assign someone to grow it for them or acquire it directly from Health Canada.
The new regulatory regime takes Health Canada largely out of the equation. Doctors will now be expected to issue their patients prescriptions for marijuana, much as they would other controlled substances, such as opioids. However, unlike other prescriptions, doctors will send the appropriate medical document directly to a licensed producer of medical marijuana. As of April 1st, these licensed producers will be the only legal source for patients to acquire marijuana for medical purposes. Licensed produces can either send marijuana directly to patients, or to a patient’s doctor.
These new regulations were opposed by most physician groups, including the Federation of Medical Regulatory Authorities of Canada and the Canadian Medical Association. These organizations argue that the new regulations continue to put patients at risk, because there is no standardization in the purity and potency of smoked marijuana, and insufficient evidence about its benefits and risks. “Doctors shouldn’t be told to prescribe marijuana until it has been subjected to the same rigorous testing and approval standards as other prescription medications,” says Rocco Gerace, Registrar of the College of Physicians and Surgeons of Ontario.
Marijuana not first-line therapy for any medical condition
Doctors considering prescribing marijuana to patients should note that marijuana is not first-line therapy for any medical condition. For nausea, ondasetron is both more potent and longer-lasting than marijuana. Likewise, there is a wide range of pain relievers with substantially better evidence than marijuana. There is a clear consensus among experts that when patients request marijuana for legitimate medical conditions, approved therapies should be tried first, and marijuana can be tried if these first-line agents fail to prove effective.
Limited evidence for the use marijuana to treat chronic pain
Herbal marijuana has not been approved by Health Canada under the same standards used to approve other prescription medications. In order for a prescription medication to be approved in Canada, its safety and effectiveness must be established through multiple phases of clinical trials.
In contrast, research into the safety and efficacy of herbal marijuana is much less extensive. Pre-clinical research has established an anatomical basis for the potential pain relieving effects of marijuana, but there have been few studies that have demonstrated effective pain relief in humans.
Randomized placebo controlled trials demonstrating the effectiveness of herbal marijuana for pain relief have focused exclusively on neuropathic pain (complex, chronic pain associated with damage to nerve fibers). These trials have been limited to neuropathic pain associated with a small number of conditions: HIV, diabetes, multiple sclerosis, surgery, and trauma (including spinal cord injury). But, Meldon Kahan, Medical Director of the Substance Use Service at Women’s College Hospital notes that research from Washington State’s medical marijuana program suggests that these are not the conditions for which most patients are seeking marijuana. “Most medical marijuana users tend to have a diagnosis of fibromyalgia, back pain or arthritis. There’s no evidence that marijuana will help these patients,” he says.
Also of concern is the safety of herbal marijuana. The intoxicating effects that have made marijuana popular as a recreational drug carry a number of known risks. In addition to the risk of dependence, these include impaired learning, memory, alertness, reaction speed and judgment, all of which affect driving and work performance. Long term use of marijuana during pregnancy can inhibit the development of neuronal pathways in fetuses and in early childhood and adolescence. In young adults, marijuana dependency can result in mild, but potentially permanent impairment of executive functions such as problem solving, and has been associated with a decline in IQ and the risk of psychosis.
In addition to the side effects associated with the intoxicating effects of marijuana, marijuana smoke contains toxic compounds. As a result, long term use of smoked marijuana can cause inflammation of the airways, resulting in chronic cough and wheezing. Marijuana smoke also appears to be a risk factor for lung cancer. Safety concerns about the effects of marijuana smoke may be alleviated somewhat by vaporizing marijuana, rather than smoking it.
Mark Ware, a scientist at McGill University and the executive director of the Canadian Consortium for the Investigation of Cannabanoids, agrees that the evidence for herbal marijuana’s safety and effectiveness is limited. “Very little research has been done to date, because the climate of prohibition made it very difficult to access research funding, legal marijuana for research purposes, and accurate use data,” he explains. He also notes that the prohibition on marijuana has meant that research has tended to focus on its harms, rather than its benefits. But Ware believes that the limited clinical research that does exist is very promising. He is hopeful that Canada’s new rules will facilitate more and better research into the safety and effectiveness of marijuana.
Pharmaceutical cannabinoids vs. herbal marijuana
While herbal marijuana has not been approved as a drug by Health Canada, several pharmaceutical cannabinoids – which contain or simulate the active ingredients found in marijuana – are approved and available in Canada. Unlike herbal marijuana, these pharmaceutical cannabinoids have undergone phase 3 clinical trials and are available in standardized dosages.
There are two pharmaceutical cannabinoids approved for use in Canada. Nabiximols (trade name Sativex) is a mouth spray that contains both cannabinoids found in marijuana: tetrahydrocannabinol (THC) and cannabidiol (CBD). Nabilone (trade name Cesamet) is a pill that mimics THC, the cannabinoid associated with the intoxicating effects of marijuana.
Kahan says that doctors who believe marijuana might help their patients should always begin by prescribing pharmaceutical cannabinoids, rather than herbal marijuana. In addition to having more robust evidence about effectiveness, pharmaceutical cannabinoids appear to be safer, he explains. Pharmaceutical cannabinoids do not tend to produce the same level of euphoria, making them less prone to abuse than smoked herbal marijuana. Also, since pharmaceutical cannabinoids are administered through pills and mouth sprays, they do not pose the same respiratory and carcinogenic concerns as smoked marijuana.
Doctors may also prefer to prescribe pharmaceutical cannabinoids, because while patients must pay out-of-pocket for herbal marijuana, nabilone is covered by both the Ontario Drug Benefit program and Alberta Health, as well as some private drug plans.
Ware agrees that doctors should try pharmaceutical cannabinoids before prescribing herbal marijuana, particularly if a doctor is relatively inexperienced with prescribing marijuana. But he does note that inhaled herbal marijuana may still have an important role to play for some patients. “Because inhaled marijuana is absorbed through the lungs, rather than the stomach, it can take effect much faster and may have a more powerful – though shorter term – effect on pain,” he says. Ware likens the difference to short-acting versus long-acting opioids, though he notes more head-to-head trials of inhaled herbal marijuana versus pharmaceutical cannabinoids are needed in order to better understand their respective clinical indications.
Screening for risk factors
Kahan urges doctors considering prescribing marijuana to screen their patients for a number of risk factors.
“Doctors should screen all patients who request medical marijuana for a cannabis use disorder and for factors that put them at risk for developing a cannabis use disorder,” he says. These risk factors include younger age, current or past problems with marijuana or other substances, as well as active mental illness. Patients with risk factors should not be given a prescription, he advises.
Patients who have a cannabis use disorder should be offered counseling and follow up, says Kahan, and those who are not able to reduce or quit should be referred to an addiction medicine doctor and/or treatment program.
Other groups at high risk of suffering side effects from marijuana include people with past or family history of psychosis, anyone under the age of 25 and pregnant women or women who may become pregnant.
Refusing to prescribe
Because of the lack of evidence about the effectiveness and safety of herbal marijuana, as well as the danger of abuse, some doctors may wish to refuse to prescribe marijuana to their patients.
In Ontario, doctors have a right to refuse to prescribe marijuana under the policies of the College of Physicians and Surgeons of Ontario (CPSO). The CPSO is currently revising this policy in light of the new federal regulations, but Gerace expects its substance to remain unchanged.
The College of Physicians and Surgeons of Alberta recommends that their members not prescribe marijuana for medical purposes.
Proceed with caution
While effective treatments have been developed for many types of chronic pain, not all treatments work for all patients. As a result, Ware believes doctors have an ethical obligation to be open to new therapies that might help patients for whom existing medications are ineffective. “The suffering of some patients is the impetus for us to continue to explore medical applications [of marijuana],” he says.
Kahan, however, worries that expanding the use of medical marijuana could put patients at risk of abuse. “The prescription opioid crisis was created when we loosened regulations around opioid prescribing,” he remarks; “I hope history doesn’t repeat itself.”
Doctors who do choose to prescribe marijuana to their patients have precious few resources to help guide them, as no clinical guidelines currently exist. These doctors are urged by experts to consider smoked herbal marijuana only after conventional therapies and pharmaceutical cannabinoids have been tried, and to screen their patients for risk factors.
Note: this article is not intended as a prescribing guide for clinicians. Doctors considering prescribing herbal marijuana or pharmaceutical cannabinoids to their patients should consult other sources, including Health Canada’s Information for Health Care Professionals: Cannabis and the Cannabinoids and Daily Amount Fact Sheet.