Physician’s Organization in Canada Releases Guidelines for Prescribing Medical Cannabis for Pain
Prescribing Patients Medical Cannabis for Pain
In December 2014, the College of Family Physicians of Canada published its preliminary recommendations for physicians recommending/prescribing smoked cannabis for chronic non-cancer pain in the organization’s journal, Canadian Family Physician. The authors reviewed the information available on cannabis for medical use, utilizing mainly level II (“well conducted observational studies”) and level III (“expert opinion”) evidence to create guidelines on the following aspects of medical cannabis use for chronic non-cancer pain:
- conditions recommended for use
- circumstances under which medical cannabis should not be recommended
- circumstances under which caution should be taken when recommending medical cannabis use
Guidelines For Canadian Physicians
The guidelines are as follows, taken verbatim from the guidelines set forth in the study:
- Smoked cannabis might be indicated for patients with severe neuropathic pain conditions who have not responded to adequate trials of pharmaceutical cannabinoids and standard analgesics (level II evidence).
- Smoked cannabis is contraindicated in patients who are 25 years of age or younger (level II evidence); who have a current, past, or strong family history of psychosis (level II evidence); who have a current or past cannabis use disorder (level III evidence); who have a current substance use disorder (level III evidence); who have cardiovascular or respiratory disease (level III evidence); or who are pregnant or planning to become pregnant (level II evidence).
- It should be used with caution in patients who smoke tobacco (level II evidence), who are at increased risk of cardiovascular disease (level III evidence), who have anxiety or mood disorders (level II evidence), or who are taking higher doses of opioids or benzodiazepines (level III evidence).
- Cannabis users should be advised not to drive for at least 3 to 4 hours after smoking, for at least 6 hours after oral ingestion, and for at least 8 hours if they experience a subjective “high” (level II evidence).
- The maximum recommended dose is 1 inhalation 4 times per day (approximately 400 mg per day) of dried cannabis containing 9% delta-9-tetrahydrocannabinol (level III evidence).
- Physicians should avoid referring patients to “cannabinoid” clinics (level III evidence).
Evaluation/Explanation of Guidelines
Generally, the regulations seem reasonable considering that the recommendations are specifically for patients with chronic non-cancer painwho are smoking their medical cannabis.
It is currently unclear whether or not cannabis use, when started in adolescence, leads to impairment in brain development. While some studies have found a link between early cannabis use and morphological brain changes, others which are more carefully controlled have found no link.
Due to the fact that cannabis use may interrupt normal brain development, children and adolescents should avoid use of cannabis unless it is deemed by a physician, in rare cases, that the potential benefits of use outweigh the risks.
History of Psychosis and Anxiety/Mood Disorders
While a link between cannabis use and certain mental health disorders has been noted, a cause-effect relationship has never been assessed. In other words, there is no definitive evidence that cannabis use actually causes mental health disorders, and the link is potentially due to the fact that those predisposed to certain mental health disorders may choose to self-medicate with cannabis.
Due to its classification as a hallucinogen, cannabis use may exacerbate certain mental health disorders, such as psychosis. Additionally, during intoxication with use of cannabis strains with higher levels of delta-9-tetrahydrocannabinol (THC), users (especially those who are inexperienced) may experience paranoia and emotional discomfort. Therefore, avoiding use in those with a past or family history of psychosis is recommended.
Anxiety and Mood Disorders
Many patients find that cannabis helps to relieve their anxiety. Regarding mood disorders, a recent study found that those with baseline major depressive disorder were more likely to begin cannabis use, but that cannabis use was not linked to an increased likelihood of having major depressive disorder. Additionally and interestingly, while “weekly to almost daily” cannabis use was associated with an increased likelihood of having baseline borderline personality disorder, daily use was not; there was also no link found between baseline borderline personality disorder and an increased likelihood to begin using cannabis. However, for those with mood and anxiety disorders, caution should be taken in using medical cannabis, for similar reasons as those noted at the beginning of this section.
Cannabis use may result in heart and vascular (i.e. blood vessel) problems in some patients (e.g. low blood pressure which can be harmful in certain diseases/disorders, potential increased risk of heart attack). While there is some evidence that cannabis use increases the risk of stroke, other evidence has suggested a decreased risk of stroke with a history of past cannabis use. Due to the fact that the impact of cannabis use on heart/vascular problems is not fully understood, use should be avoided by individuals with these health issues.
Additionally, smoking cannabis can irritate the airways and lungs. While a recent Harvard study found that low to moderate frequency of cannabis use does not result in decreased lung function in the general population, for those (1) with health issues related to the lung or (2) who also smoke tobacco (which is highly damaging to the lungs and strongly linked to the development of cancer of various organs), smoked cannabis should be avoided. Vaporization and ingestion methods are an alternative form of cannabis administration that will help to prevent additional lung damage.
Substance Abuse Disorders
Cannabis use should be avoided for patients with past cannabis or other substance abuse disorders in most cases, due to the potential for continuing or reestablishing dependence issues.
Although use of cannabis itself during pregnancy is not definitively linked to future health issues in those exposed in the womb, it has been linked to inattention, impulsivity, and hyperactivity. However, in one 1991 study of Jamaican mothers who had used cannabis during pregnancy, no differences between children exposed to cannabis in the womb vs. children unexposed to cannabis in the womb were found by age 5 (except at day 30 post-birth, when infants who had been exposed to cannabis in the womb actually had better scores on a neonatal behavioral assessment scale). While (1) the majority of studies on how cannabis use during pregnancy impacts the fetus/child have focused on heavy rather than moderate use and (2) the link between behavioral/cognitive issues in children who were exposed to cannabis in the womb may be an issue of general parental behavior/
Cannabis use may cause slowed complex reaction times and a skewing of perception of time and space. Therefore, driving while under the influence of cannabis should be avoided. However, the implications of driving under the influence of cannabis is more nuanced than the issue of those driving under the influence of alcohol, partially because medical cannabis users still need to function in their daily lives.
While cannabis use has been shown to increase lateral (side-to-side) motion within a lane, it has not been shown to impair handling, maneuvering, or turning. Some studies of drivers who have smoked cannabis alone (i.e. no additional alcohol impairment) have shown that they are no more likely than drivers who are sober to be involved in a fatal car accident, and a federal report released in February 2015 found no link between testing positive for THC (which can occur during intoxication, but also days after intoxication) and an increased risk of car crashes. This is partially due to the fact that people who have consumed cannabis tend to drive slower, leave more space between their car and the car in front of them, and are less likely to pass other cars. Alcohol has the opposite effect, and is known to greatly increase the chance of fatal accidents. Additionally, intoxicated drivers under the influence of cannabis tend to be more aware of their impairment than intoxicated drivers under the influence of alcohol, and some cannabis users who have often practiced driving under the influence show no changes in their driving behavior under the influence, as compared to driving behavior while sober. Driving under the influence of low doses (e.g. 0-4 inhalations/day of cannabis with <9% THC–often all that is needed for medical use [e.g. pain relief]) is more similar to driving under the influence of Benadryl (which should also be avoided), rather than alcohol.
However, cannabis with higher concentrations of THC or multiple inhalations may lead to more significant impairment. Due to (1) slowed reaction times, (2) skewing of time/space perception, and (3) increased lateral lane motion under cannabis intoxication, and (4) the inability for medical users to objectively assess whether or not they are experienced drivers under the influence of cannabis, those using cannabis should not drive while experiencing intoxication (i.e. psychoactive effects) and should follow the recommendations outlined in these guidelines.
Note: Driving under the influence of both alcohol and cannabis use simultaneously is more dangerous than driving under the influence of either alone, and should always be avoided.
Overall, the guidelines provided by the College of Family Physicians of Canada are well-informed, evidence-based, reasonable, and progressive. While some may find that the guidelines attempt to put too many limitations on medicinal cannabis use, safety considerations, appropriately, seem to be at the forefront of their creation. Potential improvements to the guidelines could include (1) recommendations for diseases/symptoms, other than neuropathic pain, that may be benefited by medical cannabis use, and (2) discussion of additional methods of delivery, including vaporization and ingestion, which would be useful for all practitioners, but especially for those who are uncomfortable recommending their patients smoke.
The introduction of reasonable guidelines surrounding medical cannabis use by established physician’s organizations, in Canada and worldwide, will likely help to decrease the stigma associated with/increase knowledge about medical cannabis use, especially for older and more conservative patients and physicians, thereby increasing access to this relatively safe treatment option for those in need.