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Considerations for Clinicians Looking to Advise Patients About Cannabis


It isn’t often that a nurse practitioner is mobbed by audience members at the end of a session at a psychiatry conference, but Maria Mangini, PhD, FNP-BC, has hands-on, practical knowledge about using cannabis to bring relief to thousands of patients.

It isn’t often that a nurse practitioner is mobbed by audience members at the end of a session at a psychiatry conference, but Maria Mangini, PhD, FNP-BC, has hands-on, practical knowledge about using cannabis to bring relief to thousands of patients.

During her presentation, "Cannabis Therapeutics: Advising Patients on Safe and Effective Use,” at Psych Congress 2018 in Orlando, Florida, Mangini noted that with 31 states and the District of Columbia allowing cannabis in some form, there’s confusion and reluctance among providers about how to guide their patients properly in its use. (It is also not covered by health insurers for use in cancer care).

“I’m assuming that your patients are going to ask you about cannabis,” she said to a packed ballroom, which responded with a wave of muted laughter.

She began by explaining the growing recognition of the endocannabinoid system in the human body, which influences physiological processes like pain, seizure threshold, appetite, mood, and more. It is with this system that the 2 most well-known cannabinoids interact—cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC). THC is the active component in marijuana that causes the feeling of being intoxicated or “high,” as well as dizziness, sleepiness, and disorientation.

In order to safely prescribe medical cannabis or guide patients on how to use—clinicians need to understand what Mangini called “the entourage effect.” When THC is given along with CBD, the CBD acts to blunt some of THC’s psychoactive properties, like intoxication and sedation. CBD may also counteract anxiety and depression, and may positively influence the side effect profile of cannabis, as well as the receptor binding of THC.

In a small clinical trial, 16 patients were given either 600 mg of CBD, 10 mg of THC, or a placebo. There were no acute behaviors or physiological effects from the CBD, she said.

When starting a patient out on a cannabis routine, Mangini said she advocates for starting at a low dose, setting a threshold and gradually adding to it. When Mangini starts off a patient on CBD, she begins with 5 mg per kilogram of body weight and divides the dose 3 times per day. She said she finds the optimal CBD:THC ratio is 8:1. At a lower ratio, say 2:1, the CBD will work to actually increase the undesirable effects of THC.

While there is no long-term safety data on CBD, there are no absolute contraindications; some studies report that it can block the metabolism of some kidney drugs.

CBD and THC may interact with other pharmaceuticals, she said. THC may decrease the effect of theophylline, clozapine, chlorpromazine, and other drugs, while CBD may increase the bioavailability and effect of macrolides, antihistamines, haloperidol, and sildenafil.

Terpenes, or terpenoids, also play a role, she said. Besides giving cannabis its distinctive smell, they amplify the effects of cannabinoids and reduce the psychoactivity of THC.

Mangini noted that she works in an area of the country known for cannabis usage. While many patients have access to cannabis if they want it, most physicians are not trained or have information about how to advise patients about what they need to be aware of.

With medical cannabis, there are certain things that clinicians absolutely should know about, she said. For instance, dispensary labels are not regulated, and the content may or may not be accurate. The labels don’t mention where the terpene plant content was grown, and if it is free of mold, pesticides and other contaminants.

She also noted that the effect of cannabis consumption depends on many factors, such as:

  • Dose
  • How it is administered: smoked, vaped, edibles, ointment, oral (not every form is legal in every state)
  • Timing
  • Patient health status, including age and other medications
  • Whether or not the patient is cannabis-naïve

At the end of the talk, people lined up to ask a variety of questions. One woman said her 80-year-old father has recently had his acetaminophen/oxycodone prescription discontinued by his doctor, allegedly because of a fear about the crackdown on opioid prescribers by the government, and she asked what Mangini would recommend for geriatric patients. A Florida doctor expressed frustration that pain management clinics would not work with patients who take CBD. A Kentucky doctor asked what she could do about finding “reputable” sources of CBD. And a community mental health provider asked about studies linking heavy, regular cannabis usage to dementia.

Mangini responded that those studies were not looking at medical cannabis and said if someone is smoking that much every day, “that’s not a drug problem, that’s a despair problem.”

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