Medical Marijuana Use in Older Adults

Joshua Briscoe, MD; David Casarett, MD

Disclosures

J Am Geriatr Soc. 2018;66(5):859-863. 

In This Article

Abstract and Introduction

Abstract

Symptom management in older adults, including pain and distressing non–pain symptoms, can be challenging. Medications can cause side effects that worsen quality of life or create other symptoms, and polypharmacy itself can be detrimental in older adults. Cannabinoids may offer a way of managing selected symptoms with fewer side effects. Medical marijuana is an important area of study for older adults because of the side effects of other medications. It is also important for Baby Boomers, who are likely to have more experience with marijuana than older adults of previous generations. Therefore, geriatricians should understand medical marijuana's clinical indications, adverse effects, and legal context. This article reviews the evidence regarding indications for and risks of medical marijuana use in older adults.

Introduction

Symptom management in older adults can be challenging. Medications can cause side effects that worsen quality of life or create other symptoms. Opioids in particular can increase the risk of constipation, confusion, falls, and fractures.[1,2] Benzodiazepines also increase the risk of fracture and soft tissue injury.[3] Dopamine antagonists may increase the risk of death in older adults with dementia.[4] First–generation dopamine antagonists (e.g., haloperidol) can cause extrapyramidal adverse effects, and second–generation dopamine antagonists (e.g., olanzapine) can cause metabolic disturbances.[5]

Given these problems with the current armamentarium of symptomatic interventions, cannabinoids may offer a solution. The evidence for their use is modest but continues to grow, helped by state laws that permit its use in the medical setting—so–called medical marijuana (MM). (Cannabis is the technically correct term, but marijuana will be used throughout this article because it is better known.) Marijuana contains many substances, although delta–9–tetrahydrocannabinol (THC), its best known psychoactive component, and cannabidiol (CBD) are present in the largest amounts.[6] MM is an important area of study for today's older adults because of the aforementioned burden of side effects, to which older adults may be exquisitely sensitive, and is particularly important for tomorrow's older adults as a population that is likely to have experience with marijuana grows into old age. This group will have more familiarity with using marijuana in recreational settings and will probably have different expectations and fewer reservations about using marijuana in the medical setting.[7] Therefore, geriatricians should understand MM's clinical indications, adverse effects, and legal context.

Epidemiology and Legalization

Twenty–nine states, the District of Columbia, Guam, and Puerto Rico have legalized MM; an additional 15 states allow products that are low in THC and high in CBD.[8,9] Although marijuana remains a Schedule I substance, and it is a federal crime to sell or transport it, individual states regulate MM and differ on how much marijuana they permit people to possess for medical purposes and whether individuals can grown such products or must obtain it from a dispensary. Clinicians should be mindful of these nuances as they counsel people regarding MM's therapeutic (and adverse) effects, because content may vary from state to state. Some states permit the recreational use of marijuana, which is beyond the scope of this article.

States also vary in how they regulate the physician's role in the distribution and use of MM, although in general, laws require that a physician certify that a person has a qualifying condition before the person can obtain MM from a dispensary. A prescription is not generally required.

Neurochemistry

Cannabinoids exist in 3 major categories: endocannabinoids (produced naturally by the body), phytocannabinoids (found in the cannabis plant), and synthetic cannabinoids. Although 104 cannabinoids have been identified in cannabis, at the levels typically found in the plant, THC and CBD are probably responsible for the majority of the physiological effects that result from ingestion.[10] THC is the more intensively studied and better known molecule because of its psychoactive effects, but CBD has physiological effects as well. It is not known how these effects may change as people age. In theory, the greater adiposity in older adults could create a larger depot for cannabinoids and their metabolites, which could lengthen their effective half–life, but it is not known whether this difference would have clinical significance.

THC, and to a much lesser extent CBD, binds to and activates cannabinoid receptor types 1 and 2. Endocannabinoids are involved in numerous physiological functions that can presumably be manipulated through plant– and synthetic–based means, among them being pain modulation, appetite induction, and nausea modulation.[11] The two synthetic cannabinoids approved for use in the United States are dronabinol (synthetic THC) and nabilone (a synthetic cannabinoid similar to THC).

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