In 2018, when 29 states and Washington, D.C., have medical cannabis programs and nine states allow recreational use of marijuana, it may be time for physicians to familiarize themselves with the plant.
Emergency medicine physician Charles V. Pollack Jr., MD, MA, covered the basic chemical properties of cannabis during his Friday session, “Marijuana: Its Roles, Rewards, and Risks.”
The main psychoactive component of the plant is thought to be delta-9-tetrahydrocannabinol (THC), and the main nonpsychoactive component, which seems to have anti-inflammatory properties, is cannabidiol (CBD), he explained. Currently, there are two FDA-approved cannabinoids: dronabinol and nabilone, which both come in pill form and are approved to treat nausea and vomiting associated with cancer chemotherapy, as well as wasting illnesses such as HIV and cancer, Dr. Pollack noted.
But cannabis contains at least 400 known chemical compounds, some of which have only recently begun to be understood, said Dr. Pollack, director of the Lambert Center for the Study of Medicinal Cannabis & Hemp at Thomas Jefferson University in Philadelphia.
Recent research on the plant's terpenoids and flavonoids, which produce its characteristic smell and taste, has suggested therapeutic properties of these aspects as well, he said. “These chemicals do potentially enhance cortical activity and cerebral blood flow, they can kill respiratory pathogens, and they also have some anti-inflammatory activity,” Dr. Pollack said.
However, he noted that a concept called the “entourage effect” makes studying the complete effects of cannabis challenging. “As scientists, we tend to look at isolated compounds to see what sort of biological impact they have … but when people are exposed, as they have been since the third millennium BCE, to whole-plant cannabis, then they're also getting the other cannabinoids and these terpenoids and flavonoids,” Dr. Pollack said.
The way in which all the components of the plant work together “is not at all understood,” he said, making it challenging for physicians to confidently recommend medical marijuana to patients (they cannot prescribe it). Plus, on a federal level, marijuana remains a Schedule I substance, and the only cannabis plants in the country that are approved for use in medical research are grown in one facility at the University of Mississippi.
To date, there are 53 different conditions for which states have permitted medical use of cannabis, the most common of which are insomnia, pain, cancer-related symptoms, and anxiety/post-traumatic stress disorder, Dr. Pollack said.
A 2017 report from the National Academies of Sciences, Engineering, and Medicine reviewed the conditions for which there is evidence of the effectiveness of cannabis or cannabinoids. The conditions with conclusive or substantial evidence fit on just one of Dr. Pollack's slides: chronic pain in adults (cannabis), chemotherapy-induced nausea and vomiting (oral cannabinoids), and patient-reported multiple sclerosis spasticity symptoms (oral cannabinoids).
In addition, there is moderate evidence that cannabinoids (1:1 THC and CBD) are effective for improving short-term sleep outcomes in those with sleep disturbance associated with obstructive sleep apnea syndrome, fibromyalgia, chronic pain, and multiple sclerosis, Dr. Pollack noted.
Just this week, Pennsylvania regulators added opioid withdrawal symptoms as a qualifying condition for medical marijuana treatment, but there are “zero data for that,” he said. However, many believe cannabis may be the “silver bullet” for opioid use disorder, Dr. Pollack said. “And it may be, but we're many studies and, unfortunately, probably many years away.”
Legal and scientific barriers aside, he offered some tips for providing sensible medical marijuana recommendations to patients who might benefit. “There's a lot of good doctoring associated with this,” Dr. Pollack said.
When considering the therapeutic use of cannabis in your patients, be sure to take a good history of their prior use of marijuana and marijuana products, he said. “Because if they have not used marijuana much in the past, they are likely to be very sensitive to THC. Even if you're treating something like neuropathic pain, where the data we do have suggest that higher THC as a component is important, ... start slow,” Dr. Pollack said, noting that risks include acute psychosis.
Also, be sure patients understand that, when using marijuana, they should not be driving or operating machinery, he said. Newer research has suggested that cannabis likely doesn't cause schizophrenia, Dr. Pollack said. However, it can hasten onset in predisposed patients, so in those with a personal or family history of schizophrenia, “You might want to think twice about it because you may unmask the schizophrenia by giving the patient cannabis,” he said.
Cannabis use is long on history but short on evidence, so use your best clinical judgment when advising patients and be aware that you will often be operating in an “evidence-free zone,” Dr. Pollack said. “If you're considering this … there is really no better example of the need for good doctoring and for shared decision making.”