When considering symptom control for EOL populations, polypharmacy is an issue of central importance. It is common that multiple pain and symptom control strategies are required simultaneously, creating a risk for drug-drug interactions and drug-disease interactions. Five other safety and cautionary issues associated with MC use and EOL populations emerge in the professional literature. These include: (1) physiological changes associated with aging, (2) CNS side-effects contributing to safety risks, such as falls, (3) potential drug-drug interactions associated with CBD, (4) cardiovascular side effects, and (5) quality assurance/cannabis contamination.
First, slowed hepatic and renal clearance of medicines is an expected and well-known part of the aging process. A dose of cannabinoids that is well tolerated in general populations can potentially cause unwanted side-effects for EOL populations (Abuhasira et al. 2018; Theisen 2017; Mahvan et al. 2017). Cannabis dosing for this patient group must start low with a gradual titration up until a therapeutic dose is identified. As a comparison, a healthy individual generally experiences the effect of vaporizing for one to three hours, while the same dose can last 24 hours in an individual with chronic kidney disease. An additional complication impacting cannabis dosing for all populations, including EOL, is the bi-phasic effect of THC and CBD, wherein a particular symptom control effect is achieved at a given dose, and the opposite effect occurs at both a higher and a lower dose.
Second, Mahvan et al. (2017) identify CNS side effects associated with THC, such as memory loss and ataxia, as an area of caution for elderly individuals. Additionally, Abuhasira et al. (2018) report "dizziness" as a common side effect of MC in their study of elderly patients. Issues of safety and falls prevention are already of central importance in EOL symptom management, as many effective medicines are associated with altering side effects. In 2008, very low THC/high CBD varieties of cannabis re-emerged. This development expanded interest in MC to new patient groups, such as children and elderly individuals, for whom moderate and high dose THC is not an appropriate option.
Third, CBD is associated with many potential drug-drug interactions. At sufficient levels, CBD is thought to temporarily inactivate cytochrome P450 enzymes, causing higher than expected levels of drugs that are metabolized by the cytochrome P450 system (Devitt-Lee 2015; Zendulka et al. 2016). Many common EOL drugs are metabolized by this enzyme system and therefore, may potentially interact with CBD. These drugs include steroids, benzodiazepines, anti-psychotics, and NSAIDS. Additional drugs that may interact with CBD include warfarin (Theisen 2017) and chemotherapy (Theisen 2017; Abrams 2017). These interactions are not a certainty. However, this is an area of caution, as evidence-based guidelines are currently unavailable.
Fourth, Cardiovascular effects associated with THC, such as tachycardia, supine hypertension and orthostatic hypotension are reported in the literature (Jones, 2002; Franz & Frishman, 2016). Franz & Frishman state that in healthy subjects, these effects diminish after several exposures. However, both Jones and Franz & Frishman state that some health risks may be associated with cannabis for patients with cardiovascular disease. According to Russo (2015), evidence regarding the cardiovascular effects of THC was gained in formal clinical trials associated with nabiximols. Russo reports that in early studies of nabiximols, rapid titration and high doses of THC (130 mg/day) were allowed, and adverse cardiovascular effects were seen occasionally. However, with slower titration and maximum dosing of THC at 32.4 mg/day, these effects were reduced to less than 2%. No studies exist examining the cardiovascular effects of cannabis in EOL populations.
Lastly, immunocompromise and sensitivity to chemicals is common in EOL patients. Exposure to particulate toxins (McPartland & Pruitt, 1997), and molds/fungi (McPartland & Pruitt; Ruchlemer et al. 2015) are important cannabis considerations for individuals with immune sensitivity. Particulates are reduced with the use of a vaporization apparatus (McPartland & Pruitt). Molds and fungi can be removed by various methods of sterilization, though this results in a loss of active cannabinoid compounds (Ruchlemer et al.). Systemic pesticides are also a concern for frail and EOL populations. A study by Torres et al. (2017) revealed that 86% of randomly selected cannabis clones from California's regulated industry tested positive for pesticides. Many tested positive for more than one pesticide. According to Land (2017), a chemist and faculty member at the University of California at Davis, the current problems with contamination will be avoided only by production that starts from seed, and utilizes sustainable growing methods, such as predator pests.
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