In the context of this study, the review of existing literature on therapeutic use refers to therapeutic use that is related to a diagnosis, treatment, mitigation or prevention of a disease, disorder or abnormal physical state, or its symptoms. The discussion may include both potential and/or measured benefits for older adults. Potential benefits, risks and harms are discussed because data is often limited and firm conclusions cannot always be made (Abuhasira et al., 2018; Ahmed et al., 2014; Bertram et al., 2020; van den Elsen et al., 2014; Fernando, 2018; Minerbi et al., 2019; Scott et al., 2019; Sexton et al., 2019). Some research findings fail to be generalizable to the older adult population, while others are extrapolated. Extrapolation results in products that are approved for use on the older adult population with some caution.
2.4.2 Treatment. Doctor decision making is assisted in a multitude of ways. The weighting of benefit vs risk is an important factor that doctors consider when authorizing the use of CTP. Sources include federal documents such as Health Canada’s information for health care professionals, professional organizational guidelines such as from the College of Family
Physicians of Canada (CFPC) or Canadian Nurses Association (CNA), research studies and continuing education (Abramovici, 2018; Allen et al., 2018).
2.4.2.1 Approved indications. Health products containing cannabis are only approved for a
limited number of indications in Canada: Dronabinol is used for AIDS-related anorexia and/or nausea and vomiting associated with cancer chemotherapy; Nabilone is used for nausea and vomiting associated with cancer chemotherapy; and nabiximols are used as an adjunctive treatment for spasticity from Multiple Sclerosis (MS) and/or as adjunctive treatment for neuropathic pain from MS and/or as adjunctive analgesic treatment for advanced cancer pain. Cannabidiol (CBD) is still being studied in clinical trials for use in Canada (Abramovici, 2018; Greenwich Biosciences, 2019). While these are the approved indications of health products containing cannabis, there is the potential for off-label use of these products. Examples of off label use are outlined in the section below.
2.4.2.2 Indications. Among older adults, possible indications include non-specific pain,
cancer pain, neuropathic pain, cachexia, anorexia, behavioural/mood disturbances and agitation in dementia, dyskinesia in Parkinson’s disease, chemotherapy induced nausea and vomiting, breath- lessness in Chronic Obstructive Pulmonary Disease (COPD), spasticity associated with MS and spinal cord injuries, anxiety, dystonia, Huntington's disease, Post-Traumatic Stress Disorder (PTSD), psychosis, Tourette syndrome, epilepsy, sleep disturbances, arthritis and more (Abuhasira et al., 2018; van den Elsen et al., 2014; Minerbi et al., 2019).
2.4.2.3 Contraindications. General contraindications provided by healthcare practitioners
are currently based upon the available pharmacopoeia of health products containing cannabis (Ex. dronabinol, nabilone, nabiximols) (Abramovici, 2018). These contraindications are listed in
product facts sheets and/or product monographs which are evidence based as products have undergone clinical trials. Contraindications are extended to medical cannabis products, however medical cannabis is not homogenous to the current health products containing cannabis.
There is a variety of contraindications for health products containing cannabis relevant to older adults. Contraindications for nabiximols (Sativex) include patients who are hypersensitive to this drug or to any ingredient in the formulation, including any non-medicinal ingredient, or component of the container, patients with cardiovascular diseases, such as ischemic heart disease, arrhythmias, poorly controlled hypertension, severe heart failure and patients with a history of schizophrenia or any other psychotic disorder (GW Pharmaceuticals, 2019). Nabilone (Cesamet) parallels hypersensitivity to cannabinoids and a history of psychotic disorders (Valeant Pharmaceuticals, 2009). Dronabinol (Marinol) parallels all the above while adding a contraindication for patients with significant hepatic or renal impairment (Unimed Pharmaceuticals, 2011). All three product monographs state data on the older adult population is limited and no conclusions could be made aside from recommendations to monitor patients, use caution (especially in patients with hypertension or heart disease) and titrate the dose due to “the greater frequency of decreased hepatic, renal, or cardiac function, increased sensitivity to psychoactive effects and of concomitant disease or other drug therapy” (GW Pharmaceuticals, 2019; Valeant Pharmaceuticals, 2009; Unimed Pharmaceuticals, 2011, p. 8). In addition to contraindications, there are also harms, risks and adverse events that may weigh in on a doctor’s decision to prescribe treatment of CTP.
2.4.3 Safety. Studies on the safety of cannabinoids require examining the general safety, tolerability, any adverse events (AEs) as well as pharmacokinetic (PK) and pharmacodynamic (PD) effects. Broadly, pharmacokinetics describes how drugs move throughout the body, while
pharmacodynamics describe biological responses to drugs in the body. Some common drug classes (>4 listed) potentially interacted with are antidepressants, anticonvulsants, antidiabetics, Central Nervous System (CNS) depressants, antiarrhythmic, antipsychotic, antiretroviral, opioids, hormones and immunosuppressants (See Appendix F, for a list of specific drugs). Current pharmacopeia cannot be used conclude on the safety of cannabinoids for use with the older adult population is insufficient (Abramovici, 2018; Abuhasira et al., 2018). Information direct from clinical studies on older adult use of health products containing cannabis cannot be used as all three product monographs state data on the older adult population is limited and no conclusions could be made aside from recommendations to monitor patients (GW Pharmaceuticals, 2019; Valeant Pharmaceuticals, 2009; Unimed Pharmaceuticals, 2011). Further, data on the safety of cannabinoids cannot be generalized to older adults due to the fact that PK and PD factors change with age (van den Elsen et al., 2014; Abuhasira et al., 2018).
There have only been a few studies that examined the use of cannabis in older adults. It is difficult to summarize these studies as they do not build upon one another and are distinct in their purpose, sample population, treatment methods, and dose. Overall, it appears low doses (up to 10mg) of Dronabinol (Namisol), sublingually administrated whole cannabis extracts (THC and CBD combination or CBD only), and herbal cannabis (CBD or THC rich strains) oils have a low rate of mild adverse events in older adults (Abuhasira et al., 2018; Abuhasira et al. 2019; Ahmed et al., 2014; Sexton et al., 2019). Studies on older adults stress the importance of patient monitoring by HCPs (Abuhasira et al., 2019; Minerbi et al., 2019) and dose titration (Ahmed et al., 2014; Minerbi et al., 2019) following a lack of evidence to guide treatment decisions (van den Elsen et al., 2014).
The cannabis policy environment is rapidly changing around the world, especially in Canada. Evidence in many areas of cannabis research is lacking, especially research related to older adults in both non-medical and medical populations, which makes evidence-based policy making a challenge. Clinical research capacity on cannabis has historically been limited by its classification as an illegal drug, only recently increasing via public and private improvements in licensing, funding, production capacity and vigorous dissemination of results alongside federal legalization. Older adult use of cannabis is increasing and insight from their perspectives on the use of CTP is imperative to protect the health and safety of Canadians. The next chapter examines how the current study will investigate the research objectives in outlined in the introduction.