Marijuana
Maria G. Tanzi, PharmD
Marijuana use has increased, with millions of Americans using the drug both medicinally and recreationally. A comprehensive review published in the January 28, 2020, issue of the Journal of the American College of Cardiology (JACC) highlighted cardiovascular (CV) considerations, pharmacological interactions, and clinical implications of cannabis use in patients with CV disease (CVD). Pharmacists should be aware of which of their patients are currently using cannabis products and the potential for CV adverse effects and drug–drug interactions.
“Though cannabis has shown favorable outcomes for patients with neurologic issues, it has shown harmful effects in patients with CV, in addition to interactions with a large variety of CV medications,” said study author Rhynn Malloy, PharmD, BCPS, BCCP, clinical specialist of cardiology at Brigham and Women’s Hospital. “It is important to educate patients on this risk and try to provide other treatment options to patients using this medication.”
Adverse CV effects
Cannabinoid receptors are distributed in multiple tissue beds and cells, including platelets, adipose tissue, and myocytes. Some data suggest that activation of cannabinoid receptor 1 in cardiomyocytes, vascular endothelial cells, and smooth muscle cells may result in effects such as oxidative stress, inflammation, and fibrosis.
In the acute setting, cannabis smoking may result in an increase in heart rate and blood pressure, secondary to sympathetic nervous system activation. This can be particularly problematic in those with underlying coronary artery disease. Smoking marijuana carries many of the same CV health hazards as smoking tobacco, the JACC review authors wrote.
Potential for drug–drug interactions
Malloy noted that multiple receptors are involved with cannabinoids, with the most traditional being the CYP receptors. The different components of cannabis—cannabidiol, tetrahydrocannabinol, and cannabinol—act primarily as inhibitors of CYP3A/4, CYP2D6, and CYP2C, while also acting as substrates to others. Based on potential interactions with cannabis, common medication classes that may see increased effects include calcium channel blockers, statins, beta-blockers, vitamin K antagonists, NSAIDs, and antiarrhythmic medications.
P-glycoprotein (P-gp) receptors may also be affected, with chronic exposure to cannabinoids resulting in down-regulation of P-gp and short exposure resulting in up-regulation. Unfortunately, limited clinical data are available to guide dose or therapeutic changes for these potential drug–drug interactions.
Counseling patients
Most patients tend to avoid discussing their cannabis use, as marijuana is often thought of as an “illicit” drug, said Malloy. For this reason, Malloy advised that “it is imperative to create a trusting environment where the patient feels comfortable discussing its use.” Patients are generally aware of the many negative connotations linked to marijuana use, so letting them know it’s okay to discuss it will help with the information-sharing process. Screening for cannabis use is especially important in states with prevalent use and in younger patients.
It is also important to differentiate between marijuana products when counseling patients. Traditional marijuana contains components that are different from those in CBD oil, which may also vary by product, as most are not FDA regulated.
“Once you are discussing the use of cannabis, I would begin with asking the patient what they know about the substance, and why they are using it,” said Malloy. Despite the limited data on cannabis use, there are certain indications for which the drug has been shown to have favorable outcomes, she noted. “It is important to understand the reason patients are using it in case it may be ‘the only thing that works’ versus they have not tried other therapies to treat their issues.”
By the end of the counseling session, patients with CVD should understand the potential risks of cannabis use. If appropriate, pharmacists should ask whether they may consider changing their cannabis therapy to an alternative treatment. Shared decision making is advised, especially if the patient is using marijuana for symptom management or palliative purposes. Clinicians should also consider estimates of life expectancy and CV risks.