clinician writing prescription for medical marijuana
HealthMay 26, 2021

Cannabis and CBD: A Clinician’s Guide to Advising Patients

By: Nina M. Bemben, PharmD, BCPS
Although cannabis may be legal or an accepted medical treatment in more than half the states in the U.S., it remains an illegal substance at the federal level and is NOT approved by the FDA. This creates a conundrum for clinicians who must responsibly advise those patients using cannabis while facing a lack of clinical standards and reliable evidence from which to draw.

In a recent article on the health and wellness website MedShadow, I explained that, "There is no official guidance about what medications might be contraindicated for [use in combination with marijuana], or cannabis. We also don't have official guidance about [what is] a dose of cannabis, which makes interpreting interaction information difficult."

Therefore, it is up to us as pharmacists and clinicians to stay as current as possible with changing laws and standards of practice and to strive to keep lines of communication open and honest with patients to promote safe use of cannabis and cannabis-related products and to avoid potentially harmful drug interactions.

Understanding cannabis and its challenges

Cannabis refers to the whole plant product and is generally what people mean when they talk about marijuana, either used medically or recreationally. There are also medications that are derived from cannabis, like cannabidiol (brand name Epidiolex), which is approved by the FDA for the treatment of certain seizure disorders. Dronabinol (brand name Marinol) is also derived from cannabis and approved by the FDA for nausea and vomiting related to chemotherapy and for anorexia in patients with AIDS. For the FDA-approved products cannabidiol and dronabinol, we have more information about standard dosing and drug interactions.

The quality and potency of cannabis products can vary widely. When you take a medication that's FDA-approved, like ibuprofen for example, you know exactly how many milligrams you're consuming. It's not as clear-cut with cannabis. Because cannabis itself is not FDA-approved, it's hard to compare the cannabis used in any given study to the cannabis a patient might be using at home.

Additionally, cannabis is made up of many different compounds. It can be challenging to determine whether an interaction is occurring with just one of those compounds, such as cannabidiol or another component, or the entire plant product, cannabis.

When we see news coverage of new cannabis-related studies, they're often treated equally. Some studies, however, are more reliable or provide a greater level of evidence than others.

The clinician's responsibility regarding cannabis

When making recommendations regarding any cannabis-derived product that is NOT FDA-approved, pharmacists should be familiar with the laws surrounding use of those products in their state. Every state will have different processes, procedures, and regulations, and it's important that you know what's legal in yours before making any recommendations.

Because marijuana remains illegal on federal level, some institutions may be reluctant to formally incorporate marijuana into patients' treatment plans or conduct research on marijuana due to concerns about federal enforcement. So, it's also important to be familiar with your institution's approach and any policies regarding recommendation of marijuana to patients.

To navigate any uncertainty regarding drug safety, a pharmacist can turn to a drug interaction checker like Lexi-Interact within Lexicomp. The database assigns a documentation rating to describe the level of evidence supporting a drug interaction.

Talking openly with patients about cannabis use

To recommend safe treatment, you need to draw out honest reporting of previous or current marijuana use from your patients. Telling patients why you're asking about marijuana use – in order to check for drug interactions, for example – helps to show them you are asking from a standpoint of providing care, rather than for punitive or judgmental reasons. It can also be helpful to ask all patients about marijuana (and other substance) use in a similar way, so that patients understand these are standard questions used to develop a treatment plan and that they are not being treated differently for any reason.

If the patient is taking or considering taking cannabis (or a cannabis-derived product) for a medical reason or to treat a symptom, start by reviewing with them whether there is any evidence to support that use. If there is, discuss how long it typically takes to see a response, and if there is a point at which they should stop using cannabis, either due to lack of effect or side effects.

I would always recommend a "start low, go slow" approach and encourage patients to be cautious when trying a new product. Suggest patients use the product at home first and give themselves time to see how their body responds before driving or doing other similar activities. It would also be helpful to record how well a particular product and amount worked for a patient's symptoms and any side effects they experienced to determine if any changes should be made.

To learn more about cannabis and drug interactions, read MedShadow's article "Can Cannabis or CBD Mess With My Meds?"


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Nina M. Bemben, PharmD, BCPS
Senior Clinical Content Specialist for Wolters Kluwer, Health
Nina M. Bemben, PharmD, BCPS, is a Senior Clinical Content Specialist for Wolters Kluwer, Health. She received her Doctor of Pharmacy degree from the University of Michigan College of Pharmacy. Board-certified in Pharmacotherapy, she has authored numerous publications and continuing education programs regarding pain management, palliative care, and medication management.
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Clinicians choose Lexicomp® for evidence-based drug information to support smart, safe medication decisions. Studies show that Lexicomp is the preferred drug reference solution for care teams.
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