Pharmacology of cannabis use in older adults

The advent of medicinal and recreational cannabis legalization has prompted an increase in cannabis use among all age groups. There is evidence that the increase has been greatest among older adults. Research suggests that there are many medical and psychiatric conditions for which cannabis or cannabinoids may be useful, including many conditions affecting older adults (e.g., neuropathic pain). It is therefore likely that there may be even greater uptake of cannabis use by older adults in the coming years.

Little research exists on the pharmacokinetics and pharmacodynamics of cannabis use in older individuals. Older adults are often not included in cannabis use-related studies, and occasionally are specifically excluded from this research. However, understanding the effects of cannabis on older adults is particularly important, given the increased likelihood of concomitant use with other psychoactive agents. Moreover, aging itself is associated with substantial changes in pharmacokinetics and pharmacodynamics, such as reduced hepatic drug clearance and renal elimination, and increased body fat and decreased lean body mass, which could result in an increase depot for cannabinoids and their metabolites. Taken together, it is therefore possible that previous research addressing the potentially impairing effects of cannabis may not be representative of the impacts seen in older individuals.

Emphasizing the importance of this research, the National Academies of Sciences, Engineering, and Medicine have specifically called for future research that examines “…the health effects of cannabis use in at-risk or under-researched populations, such as…and older populations (generally over 50 years of age)” and investigates “…the pharmacokinetic and pharmacodynamic properties of cannabis, modes of delivery, different concentrations, in various populations, including the dose–response relationships of cannabis and tetrahydrocannabinol (THC) or other cannabinoids” (NASEM, 2017).

Research is needed to accomplish one or more of the following specific objectives:

• Measure and compare the pharmacokinetics/dynamics among cannabis users of different ages (e.g., age groups like: young adults, middle-aged, young-old, old-old)
• Examine effects of acute administration of cannabis, using repeated fluid collection (blood) during the course of 4-6 hours
• Assess self-reported psychoactive effects of cannabis use, as well as objective measures of cognitive change

• Examine effects of cannabis interactions with:

  *   Alcohol (previous research suggests
  

  the presence of alcohol increases the level of THC in the blood)

  • Concomitant medications, particularly the most commonly prescribed psychoactive medications among older adults

• Compare and test the effects of different strains/strengths of cannabis (e.g., THC level, CBD-enriched or not) and routes of administration (smoke, vaporization, edibles, tinctures, etc.)

Of note, research studies should include consideration of:

• Inclusiveness, regarding the representativeness of sex, race/ethnicity
• Analyses (e.g., stratification) should address use history (to address possible tolerance to cannabis effects)

Research in these specific areas would generate critical information about potential differential effects of cannabis on different age groups, and in particular the “vulnerable” population of older adults with concomitant medical conditions.

National Academies of Sciences, Engineering, and Medicine (NASEM). 2017. The health effects of cannabis and cannabinoids: The current state of evidence and recommendations for research. Washington, DC: The National Academies Press. doi: 10.17226/24625.

Sets the stage for subsequent studies regarding the medical and safety impacts of cannabis use in older adults