Physicians' Knowledge of Marijuana Risks Falls Short

Batya Swift Yasgur, MA, LSW

February 27, 2018

Physicians need to be familiar with issues surrounding contemporary cannabis use so they can counsel patients regarding its risks, new research suggests.

Cannabis can cause psychosis and impaired social or occupational functioning and can create safety risks for the families of users, the investigators note.

They add that in order to provide adequate counseling, physicians must understand the patient's patterns of use, including the type, dose, and delivery method of the cannabis product.

"We noticed that many of our patients were using novel cannabis products that we didn't know much about. We realized that many physicians — including us — had only basic, often dated knowledge," lead author Jeremy Peters, DO, Department of Psychiatry, the Oregon Health and Science University, Portland, told Medscape Medical News.

The investigators undertook the review to educate clinicians, who should "absolutely initiate discussion with patients about cannabis use, even though the available time with patients is often limited," said Peters.

The review was published in the February issue of the Journal of the American Osteopathic Association.

Cannabinoid Primer

Cannabis is "one of the most widely used and controversial substances worldwide," the authors write. In the United States, its medical use, although federally prohibited, is legal in 30 states. Its recreational use is legal in eight states; both types of use are legal in the District of Columbia.

A burgeoning multibillion dollar cannabis industry has emerged, and an array of products are now available, including high-potency herbal cannabis, mass-produced cannabis edibles, cannabis oils, concentrates, and topical preparations, the researchers note.

Cannabinoids THC and CBD are the main pharmacologically active ingredients. THC binds to CB1 and CB2 receptors, and CBD appears to work as an inverse agonist at the CB1 or CB2 receptors, the authors explain.

Although ingesting THC elevates the risk for psychosis, CBD may have antipsychotic and anxiolytic properties.

There are several potential medical uses for THC, including use for analgesia in patients with chronic neuropathic or cancer pain. It has also been shown to be of benefit in alleviating spasticity associated with multiple sclerosis. Low-quality evidence suggests that cannabinoids may also help the nausea and vomiting associated with chemotherapy.

Dosing Complicated

Cannabis has increased in strength during the past half century. In the 1960s, cannabis products contained from 1% to 5% of THC by weight; today, products contain as much as 15% to 25% by weight, and even 30% or greater.

Determining the dose of THC that is consumed is complex, because its percentage by weight differs between products. Two people can smoke the same amount of the product but be exposed to different doses of THC.

The delivery method also affects the dose, because some active chemicals are lost to combustion, side stream, or exhalation, depending on how the product is taken.

The new report reviews the routes by which users are exposed to cannabis products, beginning with herbal cannabis inhaled via cigarettes, cigars, or pipes.

Intoxication can occur as soon as 2 minutes after the first inhalation. The peak effect occurs 30 minutes after use, and intoxication continues for 2 to 4 hours. Some minor effects, such as impaired working memory, can persist for more than 24 hours.

Lack of standardization makes it difficult to calculate the amount of cannabis smoked, so clinicians are advised to gather data regarding how frequently the patient purchases cannabis, the quantity typically purchased, how many bowls are smoked per ingestion, and how many times the cannabis is used before the next purchase.

The authors emphasize that only 25% of the total amount of cannabinoids in the combustible form of the product is absorbed. By contrast, the user absorbs up to 33% of the total cannabinoids present if they inhale a vaporized product.

Hashish, which consists of the compacted, sticky resin glands of the cannabis plant, is less likely to be used than other forms of herbal cannabis. It is either smoked or ingested via vapor.

Because hashish is so highly concentrated, only a small amount is needed to feel an effect, so users who are accustomed to a lower percentage of THC in herbal products may end up taking a very high dose, leading to adverse effects, such as psychosis or cognitive impairment.

Edibles, Topicals

Orally ingested cannabis products ("edibles") are becoming increasingly popular and can take the form of beverages, candies, cookies, honey sticks, butter, and cooking oils.

THC is absorbed "inconsistently" when ingested orally. It is extensively metabolized via the first-pass mechanism; effects are experienced 2 to 4 hours after ingestion and last 6 to 8 hours.

When edibles are used, more THC is required in order to feel its effect, in comparison with smoking, although the effect appears to be more intense and to last longer with edibles.

Edibles carry a particularly high risk to family members, especially children, the authors note.

"Edibles tend to be sweets, and packaging is sometimes designed to mimic familiar objects, such as candy bars," they write.

For this reason, "during clinical visits, physicians should advise cannabis users on the safe storage of cannabis products to avoid accidental ingestion by children or other cohabitants."

"A lockbox can limit accidental exposure," Peters said.

Cannabis oils are often homemade by users via grain alcohol extraction or cooking the herbal cannabis in fatty substances. These oils have become popular because they are said to have some anticancer effects, although these claims are not evidence based.

Cannabis oils are often taken orally in liquid form, sometimes incorporated into food items, and occasionally are smoked after being added to herbal cannabis.

Cannabis can also be applied topically. It is available in lotions, creams, and oils that may help with local inflammation and pain but are rarely absorbed systemically and do not lead to intoxication.

Emphasize Safety

"The most important talking points are safety related," Peters emphasized.

Even in states where recreational cannabis is legal, driving under the influence is a crime, and impaired driving is dangerous, so "patients must be reminded not to drive while intoxicated."

Additional health concerns are with regard to the potential risk for fungal infection from moldy cannabis, impaired memory and concentration, amotivationalism, and potential psychosis in patients with bipolar disorder.

Patients with bipolar disorder or social anxiety disorder should be counseled to avoid cannabis, the authors suggest.

Patients whose use of cannabis results in impaired health or impaired social and occupational functioning may be overusing the substance. Such patients should be counseled to stop or should be referred to substance abuse treatment providers, the authors recommend.

"Patients who wish to use should start with the smallest dose for desired effect, using low-THC, high-CBD strains, and clinicians should always be ready to support a patient who feels ready to quit using," Peters advised.

"Polarizing Topic"

Commenting on the review for Medscape Medical News, Walter Prozialeck, PhD, professor and chair of the Department of Pharmacology, Chicago College of Osteopathic Medicine and Midwestern University, Illinois, who was not involved with the review, said it "raises the very important issue of people responding differently to these different products and highlights that some of these products are more likely than others to cause problems in users."

Prozialeck noted that even in states that allow use of medical marijuana, many physicians are not familiar with it, so "it is hard for them to advise patients."

Moreover, in many states, "physicians who are familiar with it are not even allowed to advertise that they provide marijuana counseling."

Another issue is that few clinical studies have been conducted regarding the potential interaction between cannabis and other drugs. "Cannabinoid receptors are involved in so many processes, it would seem reasonable that they would interact with other drugs," Peters noted.

Cannabis is "often a polarizing topic," he added.

"I've had patients whose mental health greatly improved once they quit using cannabis, and I've had patients who have made amazing strides after starting medical cannabis," he recounted.

He emphasized that it is "important that we keep an open mind and continue to research cannabinoids without bias for or against its use."

The study authors and Dr Prozialeck have reported no relevant financial relationships.

J Am Osteopath Assoc. 2018;118:67-70. Full text

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