Pot Talk: Review Urges Cardiologists to Discuss Marijuana Use

With several million CVD patients in the United States estimated to be using marijuana, experts say cardiologists need to be factoring this into their conversations and sharing with their patients what’s known about the associated adverse cardiovascular risks and potential for drug interactions.

“This is increasingly becoming a common conversation that patients and clinicians are having. Patients are often seeking advice regarding the cardiovascular safety of using marijuana,” Muthiah Vaduganathan, MD (Harvard Medical School, Boston, MA), told TCTMD. “As clinicians, including cardiologists and pharmacists, it's our responsibility to provide them with the best scientific evidence.”

Vaduganathan is the senior author of a review paper published this week in the Journal of the American College of Cardiology. He and colleagues, led by Ersilia M. DeFilippis, MD (Columbia University Irving Medical Center, New York, NY), encourage a practical approach for clinicians that includes screening and testing where appropriate, especially in younger patients and in densely concentrated areas of known marijuana use. Whenever possible, they say, clinicians should be asking about frequency, quantity, and methods of administration, which can range from hand-rolled joints and pipes to vaporizers, edibles, and oils.

What Is Known

In their review of the literature, the researchers found that receptors targeted by marijuana, the cannabinoid receptors, are broadly expressed in the body, including on key tissue beds and cell types that influence the heart. On a physiological level, the acute administration of marijuana causes increases in sympathetic activity and in heart rate and blood pressure that have the potential to post safety risks for high-risk CVD patients, including those with a recent ACS. Observational studies have linked marijuana across the spectrum of CVD, including increasing the risk of MI, stroke, arrythmias, heart failure, and potentially having an impact on worsening peripheral vascular disease outcomes.

Importantly, research also indicates that marijuana is metabolized via the same pathways that many commonly administered cardiovascular therapies are metabolized, the cytochrome 450 family in the liver. 

“So, for many common therapies, dosing may actually have to be modified because the relative levels in the blood are influenced by concurrent use of marijuana,” Vaduganathan told TCTMD. Patients with known marijuana use, he added, may benefit from a multidisciplinary assessment with a pharmacist to determine what changes, if any, are needed in their medications. Therapies that may be affected by marijuana use can include antiarrhythmic drugs, calcium-channel blockers, statins, beta-blockers, and warfarin.

The review also notes that, for the first time, marijuana use exceeds cigarette smoking in the United States. An examination of the National Health and Nutrition Examination Survey suggests that 2 million of the nearly 90 million adults who reported marijuana use also had CVD.

“While that proportion is relatively small, it does suggest that overall many patients that we see in practice are using marijuana,” Vaduganathan said.

Unknowns and Gaps in Research

Other important considerations for cardiologists, he and his and colleagues note, are being in the loop regarding local regulations and legalization status of marijuana products in their state as well as being knowledgeable about available screening tools and tests. One caveat with regard to the screening tools, however, is that most of them have only been validated in adolescents and young adults, with no universally accepted method or guidelines on who should be screened.

“Only in certain select circumstances is there a structured screening pathway for marijuana use [such as] prior to heart transplantation,” Vaduganathan explained. “In other clinical scenarios, even at the time of cardiovascular events, we often may limit screening for marijuana.” He noted that discussions about screening with patients should be put into the context of safety and drug dosing.

While some cardiologists and others may not feel comfortable asking about marijuana use, especially if patients use the substance in a state where it isn’t legalized, Vaduganathan said it really comes down to viewing it as a harm reduction conversation in the same vein as drinking alcohol, smoking cigarettes, and using opioids.  

The paper notes that while significant gaps exist in the current understanding of the effects of marijuana on cardiovascular and other diseases, a big impediment to marijuana research is its designation as a Schedule I drug. According to Vaduganathan, accelerating use and legalization may provide the leverage needed to broaden research efforts in the US to match those being done in other countries.